Thèses sur le sujet « Mountain soil »

Alpine soils are young, poorly developed soils that occur above treeline. This study investigates soils located in the alpine-subalpine zone of the Wallowa Mountains, northeast Oregon. Parent material, topography, and vegetation are the most influential pedogenic factors in the high alpine landscape of the Wallowas. Soil samples were collected from the Eagle Cap Wilderness Area of the Wallowas at three mountain locations: Eagle Cap, Sacajawea, and Matterhorn. Catenas were studied in the Windblown and Minimum Snowcover zones to examine different pedogenic factors, according to the Synthetic Alpine Slope model. · Field and laboratory testing characterized the alpine soils as predominantly loamy-sands with weak structural development. The 1:1 water pH values range from 6.5 to 7.3, and the soil hues are lOYR and 2. SY in color. Soil classification characterized Eagle Cap soils as Andisols: Lithic and Typic Haplocryands. The Matterhorn and Sacajawea residuum was not classified. Parent material influence on soil development was more noticeable on granodiorite than basalt, reflecting the propensity of granodiorite to weather rapidly. Marble and shale sites lacked soil development. All the soils exhibited eolian influence, determined from silt mineralogy results. While this component did not dominate the soils as in other alpine areas, its presence was ·proven by quartz and feldspars in soils developed on marble and calcite in soils developed on granodiorite. Sodium fluoride (NaF) pH tests indicate that there is also a high aluminum content in the alpine soils, probably due to influx of Mazama volcanic ash. Krummholz and alpine turf increase the organic content of the soil, although soils beneath krummholz were not as deep. This is partially due to decreased snowcover, subsequent lack of moisture, and different parent material. All soils show a decrease in organic carbon with depth indicating that bioturbation was either low, or the soil recovered from the disturbance rapidly. Organocutans found on the bottom of rocks in the B horizon illustrate organic trans location. The increase in pH with depth shows the influence of surficial organic matter, translocated dusts, and ash. Nunatak and landmass influence on soil development was undetermined.

This study analyzes tree, soil, and microtopographic patterns present within the Cranberry Glades, a bog wetland complex located in the mountains of West Virginia. The Cranberry Glades are comprised of four open bog meadows, which provide unique habitat to several rare and endangered plant species. However, these meadows are filling in with trees and alder. This research is a study on the factors that may be involved in the processes and patterns influencing tree encroachment into the bog meadows across the open meadow â bog forest ecotone. To determine the patterns of infilling and the potential relationships among the trees, microtopography, and soil conditions, I collected and analyzed data on each of these factors within nine belt transects located across the ecotone. I gathered tree data on the following: location within transect, species, diameter at breast height or diameter at ground level, height class, associated microtopography, and growing conditions on 1,389 trees. Soil samples were gathered across the ecotone and analyzed for percent moisture, pH, and various nutrients and metals. I assessed historical aerial photographs to gain a temporal history on the patterns of infilling. The results indicate that trees decrease in density across the ecotone towards the peatland interior, and that trees are likely to be growing on hummock features and within tree islands. Soil properties resulted in mixed conclusions. The aerial photograph assessment revealed that trees and alders have been steadily encroaching into the open peatlands for at least the past 52 years. The finding of this research lend to increased knowledge on southern peatlands, wetland succession, and the Cranberry Glades Botanical Area.
Master of Science

Thesis (MSc)--University of Stellenbosch, 2001.
ENGLISH ABSTRACT: Mucoralean fungi are mostly saprotrophs that are frequently encountered in soil habitats. Using an isolation temperature of circa 25°C, other workers obtained these fungi from a wide diversity of geographical areas in southern Africa. However, it is known that psychrotolerant mucoralean fungi, able to grow at 25°C as well as at 5°C, occur in pristine Alti Mountain Grassland. Nothing is known about the diversity of these psychrotolerant soil fungi in other vegetation types of South Africa. Consequently, in this study, the psychrotolerant fungal taxa and numbers in soil from a vineyard and from pristine Mountain Fynbos were determined using an incubation temperature of 4°C and a complex isolation medium. The latter contained agar, malt extract, peptone, yeast extract, penicillin and streptomycin sulphate. Soil samples were analysed in late summer, autumn and mid-winter. It was found that, for the samples taken in late summer and autumn, the diversity of mucoralean species in the soil differed between fynbos and vineyard. In winter however, no significant difference was detected between the Shannon's diversity indices of mucoralean species in the soil samples taken from the two habitats. It was found that in both soil types, the percentage mucoralean fungi on the plates increased from summer to winter. In addition, the numbers of detectable Morlierella subgenus Morlierella on the plates were higher in winter than in late summer. The diversity of mucoralean species obtained during winter in fynbos and vineyard soil was significantly less than the diversity of these species in Alti Mountain Grassland soil. To determine if the Morlierella subgenus Morlierella isolates from the fynbos and vineyard soil, and those obtained from Alti Mountain Grassland, differ in the ability to grow at low temperatures, the radial growth rate on malt extract agar at 4°C and BOC was determined for each isolate. The results indicate that not only did seasonal changes occur in the taxa within Morlierella subgenus Morlierella, but that the isolates dominating the soil in different seasons also differed in the ability to grow at low temperatures. The percentage of isolates that had reached greater colony diameters after B days of incubation at 4°C, was higher for the isolates obtained in the cold wet month of July than for those obtained in the warmer dryer month of February. Similar results were obtained with the radial growth experiments conducted at BOC. The Morlierella subgenus Morlierella isolates obtained in winter from fynbos and vineyard soil showed less variation in low temperature growth rate than the isolates of this taxon obtained in winter from Alti Mountain Grassland soil during a previous study. This variation corresponds to the greater number (20) of Morlierella subgenus Morlierella species found in the grassland soil. Altogether only seven species of this subgenus was detected during the present study in the fynbos and vineyard soil samples. It was speculated that this difference in diversity between the fynbos and vineyard isolates, and the grassland isolates obtained in a previous study, might have been as a result of differences in the habitat or the enumeration methods used. The phylogenetic relationship between different psychrotolerant isolates of Morlierella subgenus Morlierella originating from the soil of the fynbos, vineyard and Alti Mountain Grassland, was subsequently determine through comparison of ITS regions, within ribosomal RNA repeats. Consequently, 45 psychrotolerant Morlierella subgenus Morlierella isolates originating from the three soil habitats was compared on the basis ITS 1 nucleotide sequence composition and radial growth rate at 4°C. Phylogenetic analyses showed that the isolates could be grouped into two clusters correlating with the ability to grow at low temperatures. Each cluster was further subdivided into two subgroups. It was found that except for one subgroup and the reference strain occurring in another subgroup, all the subgroups contain isolates originating from a single soil habitat. Therefore, the ITS 1 sequence of these fungi seems to indicate the original habitat and ability to grow at low temperatures. This correlation of the ITS sequence with the ecological habitat of a fungus has also been observed by other workers for other fungal groups.
AFRIKAANSE OPSOMMING: Mucoraliese fungi is meestal saprotrofe wat dikwels in grondhabitatte aangetref word. Deur gebruik te maak van 'n isolasietemperatuur van circa 25°C, het ander werkers dié fungi van 'n wye verskeidenheid geografiese gebiede in suidelike Afrika verkry. Dit is egter bekend dat die psigrotolerante mucoraliese fungi, wat in staat is om by 2SoC en ook by SaC te groei, in ongeskonde Alti Berg-Grasland voorkom. Niks is egter bekend oor die diversiteit van dié psigrotolerante grondfungi in ander veldtipes van suidelike Afrika nie. Die psigrotolerante fungustaksa en -getalle in grond van 'n wingerd en van ongeskonde Berg Fynbos is gevolglik in dié studie bepaal deur gebruik te maak van 'n inkubasietemperatuur van 4"C en 'n komplekse isolasiemedium. Laasgenoemde het agar, moutekstrak, peptoon, gisekstrak, penisillien en streptomisiensulfaat bevat. Grondmonsters is in die laatsomer, herfs en midwinter geanaliseer. Daar is 'n verskil gevind tussen die diversiteit van die mucoraliese spesies in die grond van fynbos en dié van wingerd in die monsters wat in die laatsomer en midwinter geneem is. In die winter is daar egter geen beduidende verskil gevind tussen die Shannon diversiteitsindekse van mucoraliese spesies in die grondmonsters wat uit die twee habitatte getrek is nie. In albei grondtipes is daar gevind dat die persentasie mucoraliese fungi op die plate toegeneem het van somer tot winter. Daarby was die aantal waarneembare Morlierella subgenus Morlierella op die plate meer in die winter as in die laatsomer. Die diversiteit van mucoraliese spesies wat in die winter uit fynbos- en wingerdgrond verkry is, was beduidend minder as die diversiteit van dié spesies in Alti Berg-Grasland grond. Om te bepaal of die Morlierella subgenus Morlierella isolate van die fynbos- en wingerdgrond en dié van Alti Berg-Grasland van mekaar verskil ten opsigte van hul vermoë om by lae temperature te groei, is die radiale groeitempo op moutekstrak by 4"C en aoc vir elke isolaat bepaal. Die resultate dui aan dat daar nie alleen seisoenale veranderinge in die taksa binne Morlierella subgenus Morlierella voorkom nie, maar dat die isolate wat tydens verskillende seisoene uit die grond verkry is, ook ten opsigte van hul groeivermoë by lae temperature van mekaar verskil. Die persentasie isolate wat groter kolonie diameters bereik het ná B dae inkubasie by 4°C, was hoër vir die isolate van die koue, nat Juliemaand as vir dié wat in die warmer en droër Februariemaand verkry is. Soortgelyke resultate is verkry met radiale groei-eksperimente wat by BOC gedoen is. Die MortierelIa subgenus MortierelIa isolate wat in die winter uit fynbos- en wingerdgrond verkry is, het In kleiner variasie in hul groeitempo by lae temperature getoon as die isolate in dié takson wat tydens 'n vorige studie in die winter uit Alti Berg-Grasland grond verkry is. Dié variasie stem ooreen met die groter aantal (20) MortierelIa subgenus MortierelIa spesies wat in die graslandgrond gevind is. Slegs sewe spesies van dié subgenus is gedurende die huidige studie in die fynbos- en wingerdgrondmonsters waargeneem. Daar is gespekuleer dat dié verskil in diversiteit tussen die fynbos- en wingerdisolate en die graslandisolate van die vorige studie die gevolg mag wees van verskille tussen die habitat of die enumerasiemetodes wat gebruik is. Die filogenetiese verwantskap tussen verskillende psigrotolerante isolate van MortierelIa subgenus MortierelIa uit die grond van die fynbos, wingerd en Alti Berg-Grasland, is vervolgens bepaal deur 'n vergelyking van interne getranskribeerde spasieerder (ITS) areas, binne ribosomale RNS herhalings. Daar is gevolglik 45 psigrotolerante MortierelIa subgenus MortierelIa isolate uit die drie grondhabitatte met mekaar vergelyk op grond van die basis ITS 1 nukleotied opeenvolgingsamestelling en radiale groeitempo by 4°C. Filogenetiese analises het die isolate in twee groepe verdeel op grond van hul vermoë om by lae temperature te groei. Elke groep is verder in twee subgroepe verdeel. Daar is gevind dat behalwe vir een subgroep en die verwysingstam wat in 'n ander subgroep voorgekom het, elkeen van die subgroepe bestaan het uit isolate wat van 'n enkele grond habitat verkry is. Dit wil dus voorkom of die ITS 1 opeenvolging van dié fungi 'n aanduiding gee van die oorspronklike habitat en die vermoë om by lae temperature te groei. Dié korrelasie tussen die ITS opeenvolging en die ekologiese habitat van 'n fungus is ook deur ander werkers vir ander fungusgroepe waargeneem.

Soils formed from ultramafic rocks are normally by pH values close to neutrality, a high base status and are usually rich in Mg, Fe and heavy metals. The low Ca/Mg ratio and the high heavy metal content could cause toxic effects in the biological communities. Plant communities, in particular, are usually different from nearby areas with different substrates and rich in endemisms and adapted species and subspecies. Despite their great environmental and ecological interest, pedological and ecological properties of mountain or boreal soils developed on similar substrates have seldom been studied worldwide. 198 soil pits (associated with phytosociological surveys) have been opened and analyzed in the ophiolitic area of Mont Avic Natural Park (Val d’Aosta, Western Alps, Italy), beween 900 and 2900 m above see level. Soils formed from ultramafic, mafic rocks and calcschists have been observed, in order to recognize the most ecologically important soil factors. The results show that soil properties are related with altitude and slope aspect in forest habitats, while the effect of substrate becomes important above timberline. Strong leaching in forest soils, related to high acidity and to the podzolization process, decrease the total and bioavailable heavy metal contents, above the treeline pedogenic and geomorphic processes release and accumulate large quantities of potentially hazardous trace elements. The plant communities strictly depend on the edaphic properties above the treeline, while in the forest habitats the differences caused by substrate are less discernible. Microbial and microarthropodal communities suffer stress caused by heavy metals in forest soils, while at the alpine level non significant statistical or ecological correlation are visible. Heavy metals (Ni, in particular) are the most important edaphic properties in differentiating plant communities on different substrata, while the Ca/Mg ratio (usually considered the most influencing soil properties on ultramafic soils) has no particular ecological effect.

The aim of this research is to conduct an investigation on the soils, paleosols and landforms of the area of Mt Cusna ridge (Northern Apennines - Italy) in order to define the relationship between geomorphic evolution and soil development, to characterise the main pedogenetic processes and factors acting on soils in past and present times, and to provide new information to understanding the Holocene climatic variations in the area. For this purpose, several sets of field, laboratory and microscopic analyses were carried out. A comprehensive survey of the study area allowed the production of a geomorphological map (scale 1:10000, attached to this thesis) expanding and revising the existing cartography (Panizza et al., 1982). At the same time, also the soils were surveyed and described, in order to provide a detailed characterisation of the soil types of the area. Selected soil profiles were sampled and underwent a wide set of laboratory analyses, including measurements of pH, exchangeable bases and cation exchange capacity (CEC), organic carbon content, total nitrogen and exchangeable phosphorus; along these iron oxides were investigated with the measurement of total iron and its extractable forms; grain size analyses and x-ray diffractions on the clay fraction were also carried out; finally, micromorphology of soil thin sections and SEM observations and analyses were also carried out on a subset of significant horizons. Geomorphological survey results allowed to compare the active and inactive processes. Glacial and periglacial processes, though mainly inactive since the beginning of the Holocene, still give an important forcing on the present landscape through their deposits, produced during the Last Glacial period. During the Holocene, different phases of stability and instability could be detected from the activation an reactivation of slope dynamics as the result of both climate fluctuations and structural constraints. The result is a very diversified landscape in which erosion and deposition alternate in space and time. The present day conditions are characterised by a prevalence of washout and erosion activity, mainly on lithologies more susceptible to surface processes. Soils were attributed to different landscape units, highlighting differences in processes and development between them. Degree of pedogenesis, in fact, varies from weakly developed soils on the highest and steeper areas to deep and more weathered profiles at lower elevations and/or on flatter surfaces. Among the latter, the presence of a paleosurface, characterised by the presence of paleosol units truncated and buried by colluvial deposits, has been detected in the stable areas above 1650 m a.s.l.. Laboratory geopedological analyses showed how soil in the area are characterised by being mainly silty-clayey, with low values of pH and organic C which tends to concentrate at the surface and in many cases also in the uppermost horizon of buried soil units. Iron oxides are usually present in its crystalline form, with some exceptions in peculiar soils. The crystalline/total iron ratio (weathering index) is generally low, higher inside paleosurface buried units. Clay fraction mineralogy shows the presence of quartz and chlorite inherited from parent material; neoformed clay minerals consist in illite and mixed layer clays. Micromorphological analysis mainly involved paleosurface horizons. Colluvial units show the presence of variable quantities of pedorelicts (Brewer, 1967) in their groundmass, as well as features pointing to multiple depositional events. The buried unit shows different phases of clay illuviation relatable to environmental changes. In flat areas a 2Ab horizon is found between the two units, showing accumulation of excrements and organic material; features of frost action are also present. Particular conditions are related to higher elevations as well as areas with steeper slopes. Data obtained from field and analytical approaches allowed to outline the main pedogenetic processes acting in the area. Pedogenesis started since the glacial retreat: clay mineralogy and iron oxide content are compatible with a soil formation taking place during the Holocene. The main active process in the area is Brunification (Duchaufour, 1983), which drive the development of Regosols and Cambisols (FAO, 2014); these soils are better developed at lower elevations on flat areas and stable deposits, whereas soils on steeper slopes and higher elevations show evidences of a weaker pedogenesis. Luvisols (FAO, 2014) were also formed in the past and are mainly preserved as paleosols of the buried units related to the paleosurface; moreover the clayey pedofeatures of these paleosols allowed the identification of three different clay illuviation phases, preceding the Subboreal climatic recrudescence 14C dated (Compostella et al., 2012; Giraudi, 2014). During the Late Holocene in the area appears Podzolisation (Duchaufour, 1983) as a secondary process, as testified by the presence of cryptopodzolisation features in soil profiles from different areas. Traces of this process could be also found inside the 2Ab horizon, marking the top of the buried unit in some soil profiles surveyed on the paleosurface; this horizon can be characterised as an accumulation of insect excrements and organic material developed in cold conditions. A change in vegetation cover detected by anthracological assemblages (Compostella et al., 2012) seems to confirm this hypothesis. 14C dating (Compostella et al., 2012) and frost features inside the 2Ab horizon date its burial to the Little Ice Age (LIA), which marks a phase of general erosion causing colluvial deposition also in flatter areas, which probably happened in multiple events through time. The colluvial layers show apparent pedogenesis caused by the presence of pre-weathered soil material and signs of homogenisation probably related to cryoturbation processes. Finally, the presence of frost and solifluction features inside these recent soils point to the characterisation of the LIA as a drier period in which winter precipitation were less abundant and snow cover thinner. This study outlined the existence of complex interactions between pedogenic, geomorphic and environmental processes throughout the Holocene. The influence of these aspects on soil features could be detected and used to describe and interpret the present landscape in the light of its modifications through time.

The study was carried out at Abujubeha area (10? 52 48.17 ‐11? 23 08.79 N and 30? 00 05.99 ‐ 31? 28 04.91’ E) in Northeast Nuba Mountain, South Kordofan region, Sudan. In order to investigate the soil degradation aspects in the study area, its causal, rate per time and mapping; the remote sensing and GIS technologies were used beside the routine soil survey and laboratory analyses. Quantitative information on soils degradation and vegetation cover changes was acquired. Using multi‐spectral satellite imagery the most dynamic land cover types have been able to be mapped with 64% accuracy (Dense Forest, Moderate Forest, Light Forest, Fallow and Bare soils). The result showed that 38% of the forested areas were lost in the last two decades at annual rate of 1.8%. Forest clearance in the last 5 (199‐2005) years equal two times the clearance happened in the previous 15 years (1986‐1999). The geostatistical characterization of soil variability showed that soil properties are highly spatially dependent, with significant sensitivity to soil‐forming factors. Soils dynamic are affected by land use system as well as with soil physiographic position. The Red soils (Gardud) are more dynamic than the Dark clayey soils. The Universal Soil Loss Equation (USLE) was used; the result revealed that the study area is potentially susceptible to be eroded by water. The Erosion rate was measured in term of erosion Risk Assessment. The model indicated that the overall average of soil loss is 1.32 t/ha /y.

As a response to rising wildfire hazard and forest structure and composition concerns, the National Fire and Fire Surrogate Study was established in 2000 to determine how fuel reduction and ecosystem restoration techniques might affect ecosystem properties and processes across the United States. Soil chemistry and the southern Appalachian Mountains were an ecosystem property and ecoregion of interest, respectively. Treatments utilized at this site included: prescribed fire alone (3 burns), mechanical cutting of understory shrubs and midstory trees alone (2 cuttings), and a combination of the two (2 installations). Soils were sampled in 2018 to determine potential treatment impacts for: O horizon and mineral soil (0-10 cm depth) carbon (C), nitrogen (N), carbon:nitrogen (C:N) and mineral soil calcium (Ca), magnesium (Mg), phosphorus (P), potassium (K), and pH. Results suggested slight, but statistically significant changes in O horizon C and N and mineral soil C, N, C:N, Ca, and P values from 2001-2018 differed statistically between the treatments. Soil responses differed significantly between the replications utilized in this study and also did not fully agree with results from previous sampling that occurred following the first implementation of these treatments. This research highlights the spatial and temporal nature of soil responses to management. When considered with previously reported vegetation and fuels results from this site, it appeared that prescribed burning with and without mechanical cutting presented the most promise to achieve ecosystem restoration and fuel reduction properties without altering forest soil chemistry.
Master of Science
Fire was historically present in the southern Appalachian Mountains from both natural and anthropogenic sources. A common natural cause resulted from lightning ignitions while some common anthropogenic sources resulted from Native American ignitions. Their fire-use goals included understory clearing, reduction of pests and diseases, hunting, and even warfare. These practices were adopted by early European settlers and were implemented regularly across the landscape through the late 19th century. In the early 20th century, however, fire exclusion policies were implemented across broad acreages of the continental United States. Over 80 years later, such policies led to forests that have been altered from their historic composition. Some of these alterations include changes to plant species composition. In portions of eastern United States forests, fire intolerant, shade tolerant species now exert a dominant influence beyond what would be expected in a frequently altered state. This process, referred to as mesophication, is a positive-feedback cycle that changes the composition of the forest floor, as well, as a result of the vegetative composition alterations. This cycle has led to substantial forest floor fuel accumulations comprised of vegetative litter and duff. Essentially, this policy shift and subsequent fuel alteration has potentially increased wildfire hazard when dry weather conditions and ignitions coalesce. In 2000, the National Fire and Fire Surrogate Study (FFSS) was designed and implemented to study ecosystem responses to fuel reduction treatments in 13 locations across the United States. One of these locations was the southern Appalachian Mountains near Hendersonville, North Carolina. For this particular study, soil chemistry was the observed ecosystem trait. The treatments included untreated control, prescribed fire, mechanical cutting of vegetation, and a combination of prescribed fire and cutting. From 2001-2018, 4 prescribed burns, 2 cutting treatments, and 2 combination treatments have been implemented. Prior to the first treatments in 2001, soils were sampled to determine pre-treatment soil chemistry. In 2018, soils were re-sampled to determine the potential long-term impacts of repeated implementations of these management techniques on forest soil chemistry. Overall, the results suggested that forest soil chemistry was altered in ways that do not appear biologically significant and may in fact fail to alter soils in ways that might benefit and sustain long-term ecological restoration objectives. Continued treatment applications may be necessary to obtain more desirable conditions.

We analyzed soils in Alder Bald, Grassy Bald, and Rhododendron Bald communities on Roan Mountain to infer the influence of vegetation on soil and to help guide management strategies. In all vegetation types, soils were acid (pH = 4–5) sandy loams. We found vegetation-associated differences for organic content, cation exchange capacity, acidity, two plant macronutrients (K, Mg), and three cations (Fe, Na, Zn). We predicted that nitrogen compounds would be highest in the Alder Bald because Alnus viridis ssp. crispa (Green Alder) can harbor nitrogen-fixing bacteria. Organic content was highest at the alder-bald sites, ammonium was similar among vegetation types, and nitrate was high at only some sample sites. The unique soil properties of the Alder Bald community, its likely role in primary succession, and its documentation as a long-standing community type on Roan Mountain suggest that management should be directed towards its conservation.

Site classification in the biogeoclimatic ecosystem classification system is based on three differentiating properties: climatic regimes (expressed by biogeoclimatic subzones or variants), soil moisture regimes (SMRs), and soil nutrient regimes (SNRs). A SNR represents a segment of a regional soil nutrient gradient, i.e., soils which provide similar levels of plant-available nutrients over a long period. SNRs are identified in the field using a number of easily observable soil morphological properties and indicator plant species. However, we need to know to what extent soil nutrient properties support these indirect field-estimates. There have been several studies that quantitatively characterize regional soil nutrient gradients in different climatic regions, but no study has yet been done in the subalpine coastal forest (Mountain Hemlock zone). Influenced by a maritime subalpine boreal climate, high-elevation coastal soils differ from low-elevation soils by having a thicker forest floor and a higher organic matter content. In the study summarized here, relationships between soil chemical properties and field-estimated SNRs are examined and soil chemical properties and field-identified SNRs are related to the site index of Pacific silver fir (Abies amabilis (Dougl. ex Loud.) Forbes) - one of the major timber crop species in the Coastal Western Hemlock and Mountain Hemlock zones.

The Supramontes region and Gennargentu massif are two of the most interesting territories of Central Eastern Northern Sardinia. Riparian vegetation among mountainous waterways of these territories are mainly constituted by Alnus glutinosa with other associated taxa such as Taxus baccata, Ilex aquifolium and Rhamnus persicifolia. Rare and threatened Sardinian endemic species such as Ribes multiflorum subsp. sandalioticum, Aquilegia barbaricina, Rhamnus persicifolia and Paeonia corsica grow under and close to the canopy of such riparian woods. Temperature is considered one of the major environmental factor governing seed germination in moist soil and, also is responsible for changes in dormancy states of seeds. Seed dormancy prevents germination in a specified period of time, under any combination of environmental factors that otherwise favour germination and it is mediated, at least in part, by the plant hormones abscisic acid and gibberellins. Dormancy can be broken by some environmental stimuli, such as a cold and/or warm stratification and gibberellic acid (GA) treatment. As dormancy is present throughout the higher plants in all major climatic regions, adaptation has resulted in divergent responses to the environment. Through this adaptation, germination is timed to avoid unfavourable weather for subsequent plant establishment and reproductive growth. In non-dormant seeds, the germination response to accumulated temperature could be modelled by a thermal time (θ) approach; in this model, seeds accumulate units of thermal time (°Cd) to germinate for a percentile g of the population. When seeds are subjected to temperatures (T) above a base temperature for germination (Tb), germination rate increases linearly with temperature to an optimum temperature (To), above which germination rate starts to decrease. In the sub-optimal range (To – Tb), germination occurs in the time tg, when the thermal time accumulated has reached the critical value (θg) for a percentile g of the population, and can be described as θg = (T –Tb)tg. In this work, the class of dormancy and thermal requirements for seed dormancy release and germination were investigate and/or confirmed for R. persicifolia, A. barbaricina, P. corsica and R. multiflorum subsp. sandalioticum; a thermal-time model, based on a soil heat sum approach, was developed in order to characterize its Thermal niche for germination and predict its seed germination phenology in the field.R. persicifolia showed physiological dormancy (PD), while the other three species highlighted morphophysiological dormancy (MPD); in particular, epicotyls MPD was found in P. corsica and confirmed in R. multiflorum subsp. sandalioticum. Thermal thresholds (Tb and θ50) requirements of seed germination were identified for all these species; in addition, the thermal thresholds for embryo growth was detected for A. barbaricina. The soil heat sum model developed in this work may have applicability to predictions of in situ regeneration of other species growing on Mediterranean mountain waterways. This work could confirmed that the studied species, belonging to different families placed in different phylogenetic clades, could have experienced a convergent evolution on their seed morphology and type of seed dormancy, as a response to similar environmental and climatic conditions due by the same habitat and ecosystem.

In the present thesis, implications of pasture establishment, fertilization and abandonment on soil C and nutrient dynamics were investigated for the mountain rainforest region of southern Ecuador. Over the past decades the natural forest of the study area has been threatened by conversion to cattle pastures. However, the soil fertility of these extensively grazed pastures (active pastures) declines continuously during pasture use. The invasion of bracken fern (Pteridium arachnoideum) leads to pasture abandonment when bracken becomes dominant. In order to reveal the mechanisms behind the deterioration of soil fertility, biotic and abiotic soil properties and their interaction were analyzed along a land‐use gradient (natural forest – active pasture – abandoned pasture). The ecosystem disturbance of the mountain rainforest through pasture use changed the microbial function and structure, and affected soil CO2‐C fluxes. Annually, 2 Mg soil CO2‐C ha‐1 were additionally emitted from the pasture land. This acceleration in soil respiration rates was related to accelerated rates of microbial C mineralization and fine‐root respiration. The high‐quality, N‐rich above‐ and belowground residues of the pasture grass (S. sphacelata, C4‐plant), especially the huge fine‐root biomass, provided a high C and N availability for soil microbes. Compared to the forest, increased soil pH and accelerated base saturation were further factors beneficial for soil microbial growth and metabolism of the upper mineral soil at active pastures. Three times higher amounts of microbial biomass C and a significant shift in the microbial community structure towards a higher relative abundance of Gram(‐)‐ bacteria and fungi were observed. Long‐term pasture use and the invasion of bracken (C3‐plant) diminished beneficial effects for microbes, causing a significant decrease in the C, net, and gross N mineralization rates as well as a two‐third reduction in the microbial biomass. A preferential substrate utilization of grass‐derived C4 by the soil microbes resulted in a rapid decline of the C4‐pool. As a consequence, the less available C3‐pool from bracken and former forest increased its dominance in the SOC‐pool, further decreasing pasture productivity and finally causing pasture abandonment. The lower quality and quantity of above‐ and belowground residues of the bracken (high lignin content, C/N) resulted in resource‐limited conditions that influenced the microbial function to greater extent than their structure. The microbial structure seemed to be sensitive mainly to soil pH along the land‐use gradient. Thus, a disconnection between microbial structure and function was identified. Fertilization experiments were conducted both in the lab and in the field to evaluate the impact of urea and/or rock phosphate amendment on SOM dynamics and on pasture productivity of active pastures. After combined fertilization the pasture yield was most efficiently increased by 2 Mg ha−1 a−1, indicating a NP‐limitation of grass growth. Furthermore, the fodder quality was improved by a higher content of P and Ca in the grass biomass. The microorganisms of the active pasture soil responded with an adaptation of their structure to the increased substrate availability in the short term, but did not change their initial functions in the long term. After urea/ rock phosphate addition a significant increase in the relative fungal abundance was detected, but neither a microbial limitation of energy nor of N or P was observed. However, urea addition accelerated gaseous losses of soil CO2‐C in the short term. In the study area, pronounced alterations in ecosystem functioning due to land‐use changes were detected, especially in soil C and N cycling rates. For a sustainable land‐use in this region it is crucial to prevent pasture degradation and to rehabilitate degraded pastures in order to protect the prevailing mountain rainforest ecosystem. It is of crucial importance for active pasture soils to maintain or even increase resource availability, being one indicator of soil fertility. In this context, the soil organic matter has to be retained in the long‐term to maintain high microbial activity and biomass, and thus pasture productivity. A moderate fertilization with urea and rock phosphate can be a first step to provide continuous nutrient supply for grass growth and to strengthen livestock health through increased fodder quality. However, the risk of further additional emissions of soil CO2‐C due to increased loads of urea fertilizer application has to be kept in mind. Overall, for the establishment of a sustainable land‐use management the control of bracken invasion and an adjusted nutrient management are needed. Further investigations on the reduction of soil nutrient losses and increased nutrient use efficiencies of plants, such as combined planting with legumes or the usage of cultivars with special nutrient acquisition strategies, should be in the focus of future work
In der vorliegenden Dissertation werden die Auswirkungen der Weideetablierung, ‐düngung sowie des Verlassens von Weiden auf Bodenkohlenstoff‐ und Nährstoffdynamik in einer tropischen Bergregenwaldregion Ecuadors zusammenfassend dargestellt und diskutiert. Der Naturwald des Untersuchungsgebietes ist seit Jahrzehnten durch Brandrodung und die Umwandlung in extensiv genutztes Weideland (aktive Weide) in seinem flächenhaften Bestand bedroht. Als Problem hat sich der Verlust an Fruchtbarkeit der Weideböden während ihrer Bewirtschaftung herausgestellt. Des Weiteren führt die Einwanderung des Tropischen Adlerfarns (Pteridium arachnoideum, C3‐Pflanze) zu einer Reduktion der oberirdischen Grasbiomasse. Nimmt diese Entwicklung überhand, werden die betroffenen Flächen von den Bauern nicht mehr aktiv genutzt, verlassen und neuer Regenwald gerodet. Um mehr über die Mechanismen der Verringerung der Bodenfruchtbarkeit zu erfahren, wurden biotische und abiotische Bodeneigenschaften und deren Interaktion entlang eines Landnutzungsgradienten (Naturwald – aktive Weide – verlassene Weide) untersucht. Die Zerstörung des Bergregenwaldökosystems und die Überführung der gerodeten Flächen zur Weidebewirtschaftung verändert die Funktion und Struktur der Bodenmikroorganismen und beeinflusst den CO2‐C Fluss aus dem Boden. Jährlich werden 2 t CO2‐C ha‐1 zusätzlich vom Weideland emittiert. Diese Erhöhung der Bodenatmungsraten kann mit erhöhten Raten der mikrobiellen C‐Mineralisierung und Feinwurzelatmung in Verbindung gebracht werden. Das Weidegras (S. sphacelata, C4‐Pflanze) liefert C‐ und N‐reiche ober und unterirdische organische Substanz (z.B. durch die Feinwurzelbiomasse) und trägt damit zu einer Erhöhung der C‐ und N‐Verfügbarkeit für die mikroorganismen bei. Darüber hinaus stellen ein höherer pH‐Wert und eine erhöhte Basensättigung im oberen Mineralboden der aktiven Weide günstige Bedingungen für mikrobielles Wachstum und Metabolismus dar. Als Konsequenz sind die Gehalte an mikrobiellem Biomassekohlenstoff um das Dreifache erhöht und die mikrobiellen Gemeinschaftsstrukturen signifikant in Richtung einer höheren relativen Abundanz der Gram(‐)‐Bakterien und Pilze verschoben. Eine längerfristige Weidebewirtschaftung ohne Kompensation von Nährstoffverlusten sowie die Einwanderung des Tropischen Adlerfarnes verschlechterte die Bedingungen für die Mikroorganismen, was zu einem signifikanten Rückgang des SOC, der Netto‐ und Brutto‐N‐Mineralisierungsraten sowie zu einer Halbierung der mikrobiellen Biomasse führt. Eine bevorzugte Substratnutzung von Graskohlenstoff (C4) durch die Mikroorganismen hat einen schnellen Abbau des C4‐Pools zur Folge. Somit dominiert nun der mikrobiell schlechter verfügbare C3‐Pool den Bodenkohlenstoffpool. Dies führt zu einem weiteren Rückgang der Weideproduktivität und schließlich zum Offenlassen der Weide. Die geringere Qualität und Quantität der vom Farn stammenden ober‐ und unterirdischen organischen Substanz (hoher Ligninanteil, weites C/N), führten zu einer Limitierung der Ressourcen für die Mikroorganismen, welche deren Funktionen in größerem Maße beeinflussen als deren Gemeinschaftsstruktur. Im Gegensatz dazu wird entlang des Landnutzungsgradienten die Struktur hauptsächlich durch den pH‐Wert beeinflusst. Daraus folgt, dass Struktur und Funktion der Bodenmikroorganismen voneinander entkoppelt auf Veränderungen reagieren können. Um den Einfluss von Harnstoff‐ und/ oder Rohphosphatdüngung aktiver Weiden auf die Dynamik der organischen Bodensubstanz und auf die Weideproduktivität zu untersuchen, wurden sowohl Labor‐ als auch Feldversuche durchgeführt. Im Feldexperiment wurde gezeigt, dass eine NP‐Limitierung der Grasbiomasseproduktion vorliegt und durch eine geringe NP‐Kombinationsdüngung die oberirdische Phytomasseproduktion um 2 t ha−1 a−1 gesteigert und die Futterqualität durch eine Erhöhung der P‐ und Ca‐ Gehalte verbessert werden kann. Die Mikroorganismen reagierten mit einer Anpassung ihrer Struktur an die kurzzeitig erhöhte Substratverfügbarkeit. Nach Gabe von Harnstoff und/ oder Rohphosphat wurde weder eine N‐ noch eine P‐Limitierung der Bodenmikroorganismen festgestellt, und die mikrobiellen Funktionen wurden langfristig nicht verändert. Dagegen bewirkte die Düngergabe einen erhöhten relativen Anteil der Pilzabundanz. Im Labor sowie im Feld kam es nach Harnstoffdüngung kurzzeitig zu verstärkten gasförmigen Verlusten des Bodenkohlenstoffs. Aufgrund der Landnutzungsänderungen im Untersuchungsgebiet veränderten sich die Ökosystemfunktionen stark, speziell die Boden‐C‐ und Boden‐N‐Umsatzraten. Für eine nachhaltige Landnutzung in der Region, d. h., für den Schutz der noch verbliebenen natürlichen Bergregenwaldflächen, ist es von entscheidender Bedeutung, dass die Weidedegradierung verhindert wird und degradierte Flächen wieder in Nutzung genommen werden. Als entscheidend für die Weideproduktivität hat sich in dieser Studie die Ressourcenverfügbarkeit für Bodenmikroorganismen herausgestellt. Daher ist es sehr wichtig, diese Ressourcenverfügbarkeit in Böden aktiv‐genutzter Weiden zu erhalten oder noch zu erhöhen, denn sie wirkt sich vor allem auf die organische Bodensubstanz und im Wechselspiel damit auf die mikrobielle Biomasse und Aktivität aus. Eine moderate Kombinationsdüngung aus Harnstoff und Rohphosphat ist ein erster Schritt in diese Richtung. Dabei sollte jedoch das Risiko zusätzlicher bodenbürtiger CO2‐C Emissionen in Folge höherer Düngergaben berücksichtigt werden. Für ein nachhaltiges Landnutzungsmanagement sind Maßnahmen gegen die Einwanderung des Adlerfarnes und ein angepasstes Nährstoffmanagement notwendig. Weitere Untersuchungen sollten auf eine Minimierung der Nährstoffverluste und eine erhöhte Nährstoffnutzungseffizienz der Pflanzen fokussiert werden. Weidemischkulturen aus Gräsern mit Leguminosen sowie der Einsatz von Kulturen mit speziellen Nährstoffaneignungsstrategien könnten dabei eine große Rolle spielen und sollten in der Region erprobt werden
La tesis presentada investiga el impacto del establecimiento de pasto, de su fertilización y de su manejo tradicional (abandono del pastizal) a la dinámica del carbono y de los nutrientes de suelo en la región de los bosques tropicales montañosos en el Sur de Ecuador. Durante las últimas décadas el bosque natural en el área de estudio ha estado amenazada por su conversión a pastizales. Sin embargo, la fertilidad del suelo en pastos de tipo extensivo (pastos activos) decrece frecuentemente durante el uso de los pastos. La invasión de Llashipa (Pteridium arachnoideum) conduce al abandono de los pastos cuando la ésta se vuelve dominante. Con la finalidad de revelar los mecanismos detrás de esta disminución de la fertilidad de suelo, se analizaron las propiedades bióticas y abióticas del suelo y sus interacciones, a lo largo de una gradiente del uso de la tierra (bosque natural —pasto activo — pastos abandonados). La perturbación del ecosistema de bosque tropical montañoso por su cambio de uso, mediante el establecimiento de pastizales, ha alterado la función y la estructura de los microorganismos y ha afectado el flujo de CO2‐C del suelo. Cada año 2 Mg CO2‐C ha‐1 fueron emitidas adicionalmente por el establecimiento de pastos. Esta aceleración en la tasa de respiración del suelo está relacionada con el aumento de las tasas de mineralización microbiana de carbono y de la respiración de las raíces. La alta calidad y abundancia de N de los residuos orgánicos del suelo con pasto Mequeron (S. sphacelata, C4‐planta), especialmente debido a la gran biomasa de las raíces finas, ofrecen una disponibilidad alta de C y N para los microorganismos. En comparación con el bosque natural, el aumento del pH y la saturación bases acelerada fueron condiciones más favorables para el crecimiento microbiano y para el metabolismo microbiano en el parte superior del suelo mineral en pastos activos. La cantidad de C de la biomasa de los microorganismos fue tres veces mayor que la del bosque y se ha observado un cambio significativo de la estructura de la comunidad microbiana, en donde la abundancia relativa de los hongos y de las bacterias Gram(‐) ha aumentado. El uso de pasto a largo plazo y la invasión de Llashipa (C3‐planta) han reducido los efectos benéficos para los microorganismos, que resultaron en una reducción significativa de las tasas de la mineralización de C y N, y en una reducción en dos tercios de la biomasa microbiana. El uso preferencial de los microorganismos por sustrato de pasto C4 han resultado en una rápida disminución de la reserva de C4. Como consecuencia, la menor disponibilidad de la reserva de C3 de las plantas de Llashipa y de la cobertura anterior de bosque ha incrementado su dominancia en la reserva de materia orgánica del suelo. Eso resulta, en una mayor disminución de la productividad de los pastos, conduciendo finalmente al abandono de los campos de pastos. La menor calidad y cantidad de los residuos acumulados sobre y bajo el suelo provenientes de la Llashipa han dado como resultado un sustrato de limitadas condiciones que están afectando más a las funciones microbiales antes que a su estructura. La estructura microbiana parece ser más sensible al pH del suelo a largo de la gradiente del uso de la tierra; de manera que se ha identificado una desconexión entre la estructura y función microbial. Experimentos de fertilización en laboratorio y en campo han sido realizados para evaluar el impacto de la aplicación de enmiendas (urea y/o roca fosfórica) a la dinámica de la materia orgánica y a la productividad de los pastos activos. El resultado del experimento de campo ha demostrado que la fertilización combinada es más efectiva, mostrando un aumento en la producción de biomasa de 2 Mg ha−1 a−1, lo que indica una limitación de N y P para el crecimiento del pasto. Además, la calidad de forraje se mostró incrementada ya que el contenido de P y de Ca han aumentado significativamente. Los microorganismos del suelo en el pasto activo han respondido a corto plazo con una adaptación de su estructura ante la disponibilidad de sustrato, pero no han mostrado un cambio de sus funciones iniciales a largo plazo. Después de la aplicación de urea y de la roca fosfórica, se detectó un incremento significativo en la abundancia de los hongos, pero tampoco se observó una limitación de energía microbial ni de N o P. Sin embargo, la aplicación de urea ha aumentado la pérdida gaseosa de CO2‐C del suelo a corto plazo. Debido al cambio de uso de la tierra en la área de investigación, se ha detectado una alteración notable de la función del ecosistema, especialmente en el ciclo de C y N de suelo. Para un uso sostenible de la tierra en esta región, es crucial el prevenir la degradación de pastos y rehabilitar aquellos degradados. En el suelo de pastos activos es de gran importancia el mantener o aún mejor el aumentar la disponibilidad del sustrato, que es uno de los indicadores de la fertilidad del suelo. En este contexto, la materia orgánica se debe ser retenida a largo plazo para mantener la actividad y biomasa microbiana alta y por ende la productividad de pasto. Una moderada fertilización con urea y roca fosfórica puede ser un primer paso para proveer un continuo suministro de nutrientes por el crecimiento del pasto y para reforzar la sanidad pecuaria por medio de un forraje de mayor calidad. Sin embargo, el riesgo de emisiones adicionales de CO2‐C del suelo debido a una aplicación más alta de urea debe tenerse en cuenta. Se puede concluir que para un manejo sostenible del uso de la tierra, tanto el control de la invasión de Llashipa y como un suministro adecuado de nutrientes son necesarios. Adicionalmente se podría decir que es necesario profundizar el estudio de la reducción de las pérdidas de los nutrientes de suelo y de la eficiencia del uso de los nutrientes en las plantas, así como las asociaciones de pastos con leguminosas o el uso de cultivos de absorción selectiva de nutrientes, que serían estrategias importantes para el futuro

Thesis (MScAgric (Conservation Ecology and Entomology)--University of Stellenbosch, 2005.
Within the Table Mountain National Park (TMNP), Western Cape, South Africa, various management practices have been undertaken in the removal of alien vegetation. While considerable success in the control of alien plants is evident from the removal of standing plants, it is not known if this effort has actually made any long-term difference in the effort to eliminate alien vegetation from the TMNP. This is because no coordinated effort has been made to assess the extent of the alien seed bank, nor the effect that clearing (including the use of fire) has on this seed store. This study investigates the extent of pre- and post-fire Acacia saligna seed banks under differing stand ages, differing clearing techniques and different habitats in the Cape Peninsula National Park. Firstly, the focus is on two alien plant management techniques: The first technique involves clearing and stacking of biomass for burning during winter (stack burn technique), the second technique involves burning of standing alien plants (standing/block burn technique) to decrease heat release at the surface. Secondly, the extent of Acacia species seed banks along the Silvermine River is also investigated with the aim of determining the extent of alien seed stores in this habitat and therefore the long-term restoration potential of the riparian corridor. The primary question addressed in the first study is: “Under what clearing technique will most of the alien seed bank be reduced?” The secondary question reads: “Is seed bank density and distribution directly related to age of dense infestation of the alien vegetation stand and habitat?” The primary question addressed in the second study is: “What is the vertical, lateral and longitudinal distribution and density of Acacia species seed banks along the Silvermine River?” The secondary question reads: “Is seed density and distribution influenced by above ground density of alien vegetation?” In both riparian and terrestrial systems, alien soil seed banks accumulate in high densities where aboveground alien Acacia vegetation is dense. Most of the seed occurs in the upper soil layer, but seed density decreases with depth with an exception of a high seed density at a low depth in one of the samples in the riparian system. Intense fires are most effective in reducing seed stores and removing aboveground alien vegetation in both riparian and terrestrial fynbos systems. After burns, both stack and stand burns have shown a significant decrease in seed density especially in the upper layers but there is still much seed that remained in the matrix area between stacks. The cooler winter burns resulted in less destructive, lower temperatures that aided higher seedling recruitment. Mature stands of Acacia saligna tend to have greater seed stores than immature stands and habitats with deep colluvial soils have a greater density and also greater vertical distribution of seeds. The vertical distribution of the riparian system differed from the fynbos terrestrial system in that seeds were found down to lower depths. Along the river, seed density also increased laterally with more seeds occurring in the terrrestrial sections than in the channel. Seed density increased with longitudinal distribution with more seeds occurring at the sites in the lower catchment than upper catchment. Managers should be aware that fire is needed to reduce the seed bank in both riparian and terrestrial fynbos systems. The cooler winter stack burns is the best option as it results in less destructive, lower temperatures that aids higher seedling recruitment. It is important to know the site history as age of dense infestation, number of fires and geology of site could influence seed bank density. In riparian systems the vertical distribution of seed is deeper than in the fynbos area. In order for clearing to be effective it is imperative that follow-up takes place and should be done prior to flowering to stop reseeding.

In this work some of the main factors that influence the partition and distribution of POPs in mountain environments and the behaviour of pollutants inside a pasture environment are evidenced. The variability of contamination at a local scale has been deeply analyzed in the main study area of the Andossi plateau, giving some useful information about the dependence of contamination from seasonality, soil and meteorological features. With the findings of chapter II (which gave a good definition of the horizontal, vertical and seasonal variability of contamination at local scale) and the modeling of chapter III it is possible to integrate a set of simple data (about OM content and soil temperatures) with concentration data from few samples to obtain detailed maps of potential contamination and release in a mountain environment. By knowing the local variability with a high definition it is possible to draw realistic pictures of concentration into complex alpine environments and evaluate exposure risk for the local fauna or for the domestic animals grazing on alpine pastures. In chapter IV it is reported the first field work about the different retention potential of humic substances. OM is generally considered in POPs distribution papers as a whole indistinct component of soil and its effect is only viewed as quantitative (general direct relationship between OM content and POPs concentration), but the different retention potential of humin, humic acids and fulvic acids may change this view. Moreover the three humic substances have different behaviour in terms of mobility and general ability to distribute vertically and horizontally within the soil affecting the transport of the pollutants adsorbed. In chapters V and VI the distribution into biotic matrices has been evaluated, evidencing a strict relation between soil and vegetation contamination (taking also into account local variability due to different solar exposition) and also a good relation between POPs concentration in vegetation and milk. Seasonality of contamination and grazing location could lead to different intake of contaminants by cows and so higher or lower milk contamination. The first POPs contamination data in the Mt.Meru area (Tanzania) have been reported in chapter VII and some of the findings about regional scale distribution factors have been confirmed in an equatorial area.

Vor dem Hintergrund der steigenden CO2-Konzentration in der Atmosphäre gewinnt die Rolle des Waldes als C-Speicher zunehmend an Bedeutung. Eine besonders wichtige Funktion kommt hierbei dem Boden zu, denn Böden speichern weltweit mehr C als Vegetation und boden zusammen (Brady and Weil, 2002). Im Sinne einer nachhaltigen Waldbewirtschaftung werden in Sachsen derzeit großflächig die bestehenden Nadelforsten in naturnahe, strukturierte Laub- und Laubmischwälder umgewandelt. Ziel dieser Arbeit war es daher, baumarten- und bewirtschaftungsspezifische Effekte auf den Humus und die C-Speicherung im Waldboden aufzuzeigen. Die Untersuchungsflächen wurden entlang von Waldumbausequenzen gruppiert, welche die Entwicklung von konventionell bewirtschafteten Kiefern- und Fichten-Reinbeständen zu mehr oder weniger strukturierten Rotbuchen- und Rotbuchen-Traubeneichenbeständen über die Stufe der Voranbauten widerspiegeln. Die Untersuchungen wurden im Mittleren Erzgebirge und im Nordsächsischen Tiefland durchgeführt. Zusammenfassend zeigte die Untersuchung (i) einen um 24 % höheren C-Input über den Streufall unter Laubholz, (ii) eine höhere C-Freisetzung durch die C-Mineralisierung, welche im Laufe des Jahres im Of-Horizont unter Laubholz (BuEi) um 68 % höher war als unter Ki und (iii) eine höhere Akkumulation von C unter laubholzbestockten Beständen. Die Oh-Lagen unter den untersuchten Voranbauten und Laubholzbeständen enthielten entsprechend hohe Anteile von 61 % (Bu) und 40 % (BuEi) des in der organischen Auflage gespeicherten C und auch die oberen Mineralböden enthielten deutlich höhere C-Mengen unter LH als unter NH. Die Mechanismen, welche zur C-Sequestrierung in der Oh-Lage unter BuEi führen, konnten in der vorliegenden Arbeit detailliert durch die Humusdynamik in der organischen Auflage im verlauf eines Jahres erklärt werden. Im Gegensatz indizieren die Ergebnisse unter Ki einen verzögerten, aber vergleichbar intensiven Streuabbau im L-Horizont, gefolgt von einer Phase relativer Stagnation in der Of-Lage und einer wiederum aktiven Umsatzphase im vergleichsweise geringmächtigen Oh-Horizont. Die Menge bzw. der Anteil der langfristig gespeicherten organischen Substanz wird wesentlich durch die Streuqualität bestimmt, d.h. die Qualität der Streu steuert die bestandesspezifische Humusdynamik. Neben den standörtlichen und klimatischen Faktoren ist der Einfluss der Bewirtschaftung hingegen ein Faktor, welcher sich primär auf die Abbauaktivität und somit auf die Menge des akkumulierten C auswirken. Die für das Tiefland dokumentierten Effekte werden vermutlich auch im Erzgebirge wieder relevant sein, wenn die Kalkung an Wirkung verliert. Aus der vorliegenden Arbeit kann die Schlussfolgerung gezogen werden, dass im Vergleich zur Ki in der organischen Auflage unter LH (BuEi) größere Mengen C aktiv umgesetzt werden und in Folge dieser spezifischen Humusdynamik größere Mengen C in der Oh-Lage und im Mineralboden gespeichert werden können
Against the background of the increased CO2 concentration of the atmosphere the role of the forest as C store gains interest. An especially important function comes up to soil as soils sequester more C than vegetation and atmosphere together on a global scale (Brady and Weil, 2002). In the sense of a sustainable forest management of Saxony the vast areas covering coniferous stands are currently converted to semi-natural and structured deciduous and mixed forests. It was thus, the aim of this study to show species- and management-specific effects on humus dynamics and to evaluate top soils as possible C sink. All study sites involved were arranged along sequences representing the development from pure and conventionally managed Scots pine or Norway spruce stands to more or less structured European beech or European beech/Common oak stands via advanced plantings. The study was performed in the Ore mountain region and lowland of Saxony. In sum, the study revealed (i) a by 24 % higher litter-derived C input in the deciduous stand, (ii) a higher release of C by potential C mineralisation, that was in mean of one year by 68 % significantly higher in the F layer under beech/oak than under pine, and (iii) a higher accumulation of C under deciduous stands. The H layer under the studied advanced plantings and deciduous stands contained higher portions of 61 % (beech) and 40 % (beech/oak) of the total C accumulated in the organic layer and also upper mineral soil held evidently higher C under deciduous than under the pine stand. The specific mechanisms of C storage in the H layer under the beech/oak stand were explained in detail by explaining humus dynamics in the different horizons throughout the year. In contrast, the results under pine indicate a retarded, but as intensive decomposition in the L layer, followed by a phase of relative stagnancy (F layer) and in turn again active turnover phase in the comparatively thin H layer. The amount and portion of the long-term sequestered organic matter is substantially affected by the quality of the litter, that is that litter quality rules the stand-specific humus dynamics. Besides the site- and climate-specific factors, forest management in contrast is a factor, that affects turnover activity and thus, the amount of C accumulated. The effects documented for the lowland will presumably be relevant in the Ore Mountain region once the lime looses its effect. It can be concluded that in comparison to pine in the organic layer under deciduous trees (i.e., beech/oak) a higher amount of C is actively turned over and subsequently of this specific humus dynamics a higher amount of C is sequestered in the H layer and in mineral soil

Vor dem Hintergrund der steigenden CO2-Konzentration in der Atmosphäre gewinnt die Rolle des Waldes als C-Speicher zunehmend an Bedeutung. Eine besonders wichtige Funktion kommt hierbei dem Boden zu, denn Böden speichern weltweit mehr C als Vegetation und boden zusammen (Brady and Weil, 2002). Im Sinne einer nachhaltigen Waldbewirtschaftung werden in Sachsen derzeit großflächig die bestehenden Nadelforsten in naturnahe, strukturierte Laub- und Laubmischwälder umgewandelt. Ziel dieser Arbeit war es daher, baumarten- und bewirtschaftungsspezifische Effekte auf den Humus und die C-Speicherung im Waldboden aufzuzeigen. Die Untersuchungsflächen wurden entlang von Waldumbausequenzen gruppiert, welche die Entwicklung von konventionell bewirtschafteten Kiefern- und Fichten-Reinbeständen zu mehr oder weniger strukturierten Rotbuchen- und Rotbuchen-Traubeneichenbeständen über die Stufe der Voranbauten widerspiegeln. Die Untersuchungen wurden im Mittleren Erzgebirge und im Nordsächsischen Tiefland durchgeführt. Zusammenfassend zeigte die Untersuchung (i) einen um 24 % höheren C-Input über den Streufall unter Laubholz, (ii) eine höhere C-Freisetzung durch die C-Mineralisierung, welche im Laufe des Jahres im Of-Horizont unter Laubholz (BuEi) um 68 % höher war als unter Ki und (iii) eine höhere Akkumulation von C unter laubholzbestockten Beständen. Die Oh-Lagen unter den untersuchten Voranbauten und Laubholzbeständen enthielten entsprechend hohe Anteile von 61 % (Bu) und 40 % (BuEi) des in der organischen Auflage gespeicherten C und auch die oberen Mineralböden enthielten deutlich höhere C-Mengen unter LH als unter NH. Die Mechanismen, welche zur C-Sequestrierung in der Oh-Lage unter BuEi führen, konnten in der vorliegenden Arbeit detailliert durch die Humusdynamik in der organischen Auflage im verlauf eines Jahres erklärt werden. Im Gegensatz indizieren die Ergebnisse unter Ki einen verzögerten, aber vergleichbar intensiven Streuabbau im L-Horizont, gefolgt von einer Phase relativer Stagnation in der Of-Lage und einer wiederum aktiven Umsatzphase im vergleichsweise geringmächtigen Oh-Horizont. Die Menge bzw. der Anteil der langfristig gespeicherten organischen Substanz wird wesentlich durch die Streuqualität bestimmt, d.h. die Qualität der Streu steuert die bestandesspezifische Humusdynamik. Neben den standörtlichen und klimatischen Faktoren ist der Einfluss der Bewirtschaftung hingegen ein Faktor, welcher sich primär auf die Abbauaktivität und somit auf die Menge des akkumulierten C auswirken. Die für das Tiefland dokumentierten Effekte werden vermutlich auch im Erzgebirge wieder relevant sein, wenn die Kalkung an Wirkung verliert. Aus der vorliegenden Arbeit kann die Schlussfolgerung gezogen werden, dass im Vergleich zur Ki in der organischen Auflage unter LH (BuEi) größere Mengen C aktiv umgesetzt werden und in Folge dieser spezifischen Humusdynamik größere Mengen C in der Oh-Lage und im Mineralboden gespeichert werden können.
Against the background of the increased CO2 concentration of the atmosphere the role of the forest as C store gains interest. An especially important function comes up to soil as soils sequester more C than vegetation and atmosphere together on a global scale (Brady and Weil, 2002). In the sense of a sustainable forest management of Saxony the vast areas covering coniferous stands are currently converted to semi-natural and structured deciduous and mixed forests. It was thus, the aim of this study to show species- and management-specific effects on humus dynamics and to evaluate top soils as possible C sink. All study sites involved were arranged along sequences representing the development from pure and conventionally managed Scots pine or Norway spruce stands to more or less structured European beech or European beech/Common oak stands via advanced plantings. The study was performed in the Ore mountain region and lowland of Saxony. In sum, the study revealed (i) a by 24 % higher litter-derived C input in the deciduous stand, (ii) a higher release of C by potential C mineralisation, that was in mean of one year by 68 % significantly higher in the F layer under beech/oak than under pine, and (iii) a higher accumulation of C under deciduous stands. The H layer under the studied advanced plantings and deciduous stands contained higher portions of 61 % (beech) and 40 % (beech/oak) of the total C accumulated in the organic layer and also upper mineral soil held evidently higher C under deciduous than under the pine stand. The specific mechanisms of C storage in the H layer under the beech/oak stand were explained in detail by explaining humus dynamics in the different horizons throughout the year. In contrast, the results under pine indicate a retarded, but as intensive decomposition in the L layer, followed by a phase of relative stagnancy (F layer) and in turn again active turnover phase in the comparatively thin H layer. The amount and portion of the long-term sequestered organic matter is substantially affected by the quality of the litter, that is that litter quality rules the stand-specific humus dynamics. Besides the site- and climate-specific factors, forest management in contrast is a factor, that affects turnover activity and thus, the amount of C accumulated. The effects documented for the lowland will presumably be relevant in the Ore Mountain region once the lime looses its effect. It can be concluded that in comparison to pine in the organic layer under deciduous trees (i.e., beech/oak) a higher amount of C is actively turned over and subsequently of this specific humus dynamics a higher amount of C is sequestered in the H layer and in mineral soil.

The three major components in the site classification of the biogeoclimatic ecosystem classification system are: climatic regimes, soil moisture regimes (SMRs) and soil nutrient regimes (SNRs). Both SMRs and SNRs can be identified in the field using soil characteristics and indicator plants. In the case of SMRs a quantitative classification was also developed that allow comparison of SMRs in different subzones. However, similar quantitative classification has not yet been developed for SNRs. This pamphlet summarizes and compares the results of several regional studies conducted in different biogeclimatic zones. Each of theses studies aimes to develop a quantitative SNR classification (Table 1). The comparison will examine: (1) how well the field-based classification matches quantitative classification, and (2) which direct measures distinguish best between field-identified SNRs.

Les composés semi-volatils, organiques et inorganiques, sont présents dans tous les compartiments de l'environnement. Bien que la plupart soit d'origine anthropique, une partie peut être produite naturellement (certains HAP et métaux). Du fait de leur persistance et de leur faible dégradabilité, ces polluants sont transportés, dans l'atmosphère, à plus ou moins longue distance de leurs sources d'émission, se déposent dans différents médias (végétation, eau, sol), où ils sont stockés temporairement ou définitivement. Par l'intermédiaire de cycles géochimiques (succession de dépôts-émission), ils contaminent l'ensemble de l'environnement, y compris les milieux les plus reculés. Le travail réalisé a permis d'étudier la spéciation et le devenir des polluants à l'interface sol-air, en plaine et en zone de montagne. Une triple approche a été menée pour définir le rôle du sol dans le piégeage ou la volatilisation des polluants. La première partie du travail a consisté à déterminer, en microcosme, les principaux paramètres contrôlant les émissions des sols de montagne, dont la température, l'humidité de l'air, la teneur en matière organique et la fraction en eau du sol. À partir de ces mesures, une approche thermodynamique a permis de prédire le mécanisme de transfert des HAP en fonction des propriétés physicochimiques des composés ciblés et des sols. En parallèle, des essais de terrain ont permis : (i) de préciser la nature des polluants rencontrés dans l'air et les sols de chaque site ; (ii) de déterminer le mode de contamination ; (iii) d'estimer la variabilité saisonnière des échanges à l'interface sol-air. Un nouveau préleveur a été développé pour estimer les émissions des composés volatils des sols en phases particulaire et gazeuse. Des bilans matières ont été établis pour préciser le rôle du sol. Une dernière approche par modélisation finalise le travail. A partir des mesures réalisées sur le terrain et en laboratoire, deux modèles, SOIL et LEVEL, ont été utilisés permettant de : (i) de prédire la répartition d'un composé dans l'environnement ou dans les fractions du sol ; (ii) d'estimer les voies de perte et d'échanges entre le sol et l'atmosphère. Ces simulations ont finalement été comparées aux données expérimentales pour vérifier la validation.

Les sols de montagne représentent d'importants réservoirs de carbone (C) potentiellement vulnérables aux changements climatiques et changements d'usage qui les affectent de manière amplifiée. Or la grande variabilité de ces milieux, leur faible accessibilité ainsi que le manque d'outils de mesure appropriés limitent nos connaissances qui restent aujourd'hui très fragmentaires en ce qui concerne les stocks, la chimie et la réactivité du carbone organique des sols (COS). Ces informations sont pourtant nécessaires pour appréhender l'évolution de ces sols et de leur C dans ce contexte de changements globaux. Les objectifs de ce travail de thèse étaient (i) d'accéder à une meilleure compréhension de la nature, de la stabilité et de la vulnérabilité du COS dans une mosaïque d'écosystèmes des Préalpes calcaires (massif du Vercors), (ii) de rechercher des outils de caractérisation rapides et fiables adaptés à l'étude et au suivi du COS à l'échelle du paysage, et enfin (iii) de proposer des indices pour l'évaluation et le suivi de la qualité des sols en milieu de montagne. Dans un premier temps, nous avons testé l'application de la pyrolyse Rock-Eval pour l'étude du COS à grande échelle sur un ensemble d'unités écosystémiques. Nous avons ensuite comparé la pyrolyse Rock-Eval à deux techniques classiques d'étude de la matière organique du sol (MOS) : le fractionnement granulodensimétrique de la MOS et la spectroscopie moyen infrarouge. Ces approches analytiques couplées nous ont permis de quantifier les stocks de C à l'échelle de la zone d'étude et d'expliquer la stabilité et la vulnérabilité du COS sous des angles variés. Les facteurs responsables des patrons observés dans les différentes unités écosystémiques sont discutés. Ce travail a également confirmé la pertinence de l'outil Rock-Eval pour répondre aux objectifs fixés. Parallèlement, des approches biologiques nous ont permis d'évaluer l'importance de la composante microbienne dans ces sols. Enfin, des indices évaluant le statut organique des sols (stockage de COS, fertilité des sols, vulnérabilité du COS) sont proposés pour constituer des outils de gestion et d'aide à la décision
Mountain soils are major reservoirs of carbon (C), potentially vulnerable to climate and land use changes that affect them significantly. However, the great variability of these soils, their limited accessibility and the lack of appropriate measurement tools restrict our knowledge. Today, our comprehension of the biogeochemistry of mountain soils remains very incomplete regarding stocks, chemistry and reactivity of soil organic carbon (SOC). Yet this information is necessary to understand the evolution of soil carbon in the current context of global change. The objectives of this work were (i) to gain a better understanding of the nature, stability and vulnerability of SOC in a mosaic of ecosystems in a calcareous massif in the Alps (Vercors massif), (ii) to search for fast and reliable characterization tools, suitable for the study and monitoring of COS at the landscape scale, and (iii) to propose indicators for the assessment and monitoring of soil quality in mountain regions. As a first step, we tested the application of Rock-Eval pyrolysis for the study of COS at large-scale on a set of ecosystem units. Then, we compared the Rock-Eval approach to two conventional techniques for soil organic matter (SOM) study: the particle-size fractionation of SOM, and the mid-infrared spectroscopy. These coupled analytical approaches allowed us to quantify C stocks across the study area, and explain the stability and the vulnerability of COS at various angles. Factors responsible for the patterns observed in the different eco-units are discussed. This work also confirmed the relevance of the Rock-Eval tool to achieve our previous objectives. Biological approaches allowed us to assess the significance of microbial pool in these soils. Finally, indices assessing the status of SOM (SOC storage, soil fertility, vulnerability COS) were proposed and constituted interesting management tools for decision-makers

Prevention of uncontrolled wildfire and restoration of Rocky Mountain forests can be accomplished through ecosystem restoration practices such as thinning followed by prescribed fire. The objective of this study is to determine how much thinned fuel can be left on the ground without causing fire temperatures high enough to impair soil physical, chemical and biological properties. I assess the effects of different fuel loadings on soil properties (forest floor depth, soil pH, carbon and nutrient levels, and soil bacteria and fungal communities) during the first year after fire and explore relationships among fuel loadings, fire temperatures and indicators of soil health. Five fuel management treatments were assessed: large piles, small piles, areas of cut-and-leave, deep litter and an unburned control. In all burned treatments, fuel loadings were greatly reduced and maximum temperatures at the forest floor surface ranged from 60 to 850°C. Temperatures were over 300°C for over 3 hours in the large-pile treatment but were lower and of shorter duration in the small-pile and cut-and-leave treatments. The deep-litter treatment had temperatures above 200°C for over 2 hours and complete combustion of the forest floor occurred. The low moisture content and resulting consumption of the forest floor in the deep-litter treatment resulted in the largest negative impacts on soil chemical and microbiological properties, while few significant differences were evident among the other treatments. Higher nitrate availability and significant increases in pH were found in the forest floors of burned plots and in the mineral soil of the deep-litter treatment. Microbial abundance did not recover to pre-fire levels in any burned treatments after one year, which may be attributed to the persistence of significant increases in pH.

Global change phenomena, such as forest disturbance and land-use change significantly affect elemental balances as well as the structure and function of terrestrial ecosystems. Inappropriate land management often causes nutrient losses and finally soil degradation and loss of soil functioning. Especially in tropical ecoregions, soil degradation by nutrient losses is widely abundant. Soil microorganisms are the proximate agents of many processes performed in soils and are regarded as sensitive bio-indicators. However, the incorporation of microbial responses to the definition of critical soil conditions is not intensively developed. In the present thesis, several data analyses of the relationships between ecosystem disturbance and land-use change (natural forest, pastures of different ages, secondary succession) and a diverse set of soil ecological characteristics in the tropical mountain rainforest region of southern Ecuador were compiled. In particular, it was tested whether soil microbial biomass and community functioning were sensitive to land-use change effects. Furthermore, an information-theoretic approach was applied to find the factors that regulate soil microbial biomass and community function. Finally, in a nutrient enrichment experiment the above- and belowground responses to N and P additions were examined. The tested research questions and results were linked to the theory of ecological stoichiometry in order to connect the research to a sound and unifying scientific basis. Soil and microbial stoichiometry were affected by both land-use change and soil depth. After forest disturbance, significant decreases of soil C:N:P ratios at the pastures were fol-lowed by increases during secondary succession. Microbial C:N ratios varied slightly in response to land-use change, whereas no fixed microbial C:P and N:P ratios were observed. Shifts in microbial community composition were associated with soil and microbial stoichiometry. Strong positive relationships between PLFA-markers 18:2n6,9c (saprotrophic fungi) and 20:4 (animals) and negative associations between 20:4 and microbial N:P point to land-use change affecting the structure of soil food webs. Significant deviations from global soil and microbial C:N:P ratios indicated a major force of land-use change to alter stoichiometric relationships and to structure biological systems. Data analysis reveals a strong impact of land-use change on soil microbial biomass, C-mineralization, gross-NH4-consumption and –production rates. According to the results of the IT-approach, combined models better describe effects of land-use change on soil microorganisms than single explanation models. Microbial resources and soil chemical environment were important pre-dictors for soil microbial biomass and community functioning. Little is known about the environmental drivers of the catalytic properties of EHEs (e.g., pH, nutrients) and their functional link to the structure of soil microbial communities. The activities of the six hydrolytic enzymes were tested. Microbial production of AP responded to the low P status of the sites by a higher investment in the acquisition of P compared to C. Three major drivers of enzyme activities were found to be significant for enzyme production: 1.) Microbial demand for P regulated the production of AP, provided that N and C were available. At the natural forest site the two-fold higher specific activity of AP pointed to a high microbial P-demand, whereas the production of AP was constrained by the availability of N and DOC after pasture abandonment. 2.) Microbial biomass that was controlled by pH and resource availability was the main driver for CBH, BG and NAG activities. 3.) Substrate induction due to increased litter inputs of herbaceous plant species seemed to regulate AG and XYL activities during secondary succession. The enzymes’ affinity to substrate, as a potentially critically enzyme kinetic parameter is understudied. The data analysis suggests that microbial communities adapted to environmental changes, demonstrated high flexibility of extracellular enzyme systems and selected for enzymes with higher catalytic efficiency compared with pure cultures. Under in situ conditions, enzyme-specific environmental drivers of the Km, e.g., the pH for XYL, the C:N ratio for AP, and the C availability for NAG were found. The data demonstrated that the higher substrate affinity of XYL and AP was associated with more abundance of Gram(-) bacteria. The catalytic efficiency of enzymes decomposing cellulose, hemicellulose, and starch positively correlated with the relative abundance of Gram(-) bacteria. The turnover rate of the tested substrates was three to four times faster at the young pasture site compared with the longterm pasture and secondary succession sites. Nutrient inputs by atmospheric deposition are known to affect terrestrial ecosystems. However, little is known about how N and P co-limited ecosystems respond to single nutrient enrichment. In this work the susceptibility of above- and belowground ecosystem compo-nents and of their linkages in an N and P co-limited pasture to N- and P-enrichment was assessed. It was tested if the plants´responses can be explained by the concept of serially linked nutrients introduced by Ågren (2004). In this concept, the control of the growth rate by one nutrient is assumed to depend on the control of a different cellular process by another nutrient. The responses of shoot and root biomass and C:N:P stoichiometry of the grass Setaria sphacelata (Schumach.) to moderate N, P, and N+P application over five years were investigated. In addition, the effects of nutrient enrichment on soil nutrient pools, on arbuscular mycorrhizal fungi (AMF) as well as on microbial biomass, activity, and community structure were tested. In order to evaluate the importance of different factors explaining microbial responses, a likelihood-based information-theoretic approach was applied. The application of N+P increased aboveground grass biomass. Root biomass was stimulated by P-treatment. Grass C:N:P stoichiometry responded by altering the P-uptake or by translocating P from shoot to root. In particular, root C:N and C:P stoichiometry decreased in P- and in N-treatment. Extractable fractions of soil C, N, and P were significantly affected by nutrient enrichment. P application increased the biomass of Gram-positive bacteria and the abundance of AMF, however, results of the IT-approach suggested indirect effects of nutrient enrichment on microbes. The responses of the N and P co-limited pasture to particular nutrient enrichment support the concept of serially linked nutrients. The present study provides evidence for the fundamental importance of P for controlling resource allocation of plants in responses to nutrient enrichment. Resource allocation of the grass rather than direct effects of nutrient additions drives changes in AMF, microbial biomass, community structure, and activity
Seit dem Übergang vom Holozän zum Anthropozän greift der Mensch immer stärker in globale und regionale Stoffkreisläufe ein. Durch die Zerstörung von Naturwäldern und Landnutzungswandel werden die Strukturen und die Funktionen der Ökosysteme stark verändert. Unangepasste Landnutzung führt zu Nährelementverlusten, die mittel- bis langfristige zur Bodendegradation und zur Reduktion von Bodenfunktionen führen. Solche Veränderungen sind insbesondere in den Tropen zu beobachten. Bodenmikroorganismen spielen in den Stoffkreisläufen eine zentrale Rolle. Zudem sind sie sensitive Bioindikatoren für den Zustand von Ökosystemen. Im Gegensatz dazu, werden die Bodenmikroorganismen noch nicht ausreichend für die Zustandsbewertung von Ökosystemen verwendet. In der vorliegenden Dissertation werden verschiedene Datenanalysen zu den Beziehungen von Landnutzungswandel (Naturwald, Weiden verschiedener Alter, sekundäre Sukzession) und den Eigenschaften der Bodenmikroorganismen in einer tropischen Bergregenwaldregion Süd-Ecuadors zusammengefasst. Ein besonderer Fokus lag darauf zu prüfen, ob die mikrobielle Biomasse und die Funktionen die von der mikrobiellen Gemeinschaft geleistet werden (z.B. Enzymaktivitäten) durch den Landnutzungswandel beeinflusst werden. Ein informations-theoretischer Ansatz wurde verwendet um verschiedene Erklärungsansätze der steuernden Faktoren vergleichend zu testen. Darüber hinaus wurden in einem Weidedüngungsexperiment die Reaktionen der ober- und der unterirdischen Ökosystemkomponenten auf die Anreicherung mit N und P getestet. Um die Ergebnisse auf eine breite wissenschaftliche Basis zu stellen wurde die Untersuchungen in den Kontext der Theorie die Ökologischen Stöchiometrie eingeordnet. Die C:N:P Stöchiometrie im Boden und in den Mikroorganismen veränderte sich durch den Landnutzungswandel und mit der Bodentiefe. Mit der Weideetablierung nahmen die C:N:P Verhältnisse im Boden deutlich ab, stiegen dann nach dem Verlassen der Weiden im Zuge der sekundären Sukzession wieder an. Das mikrobielle C:N Verhältnis variierte nur leicht, dagegen zeigten das C:P und N:P Verhältnis deutliche Veränderungen durch den Landnutzungswandel. Mit diesen Veränderungen in der Boden- und Organismenstöchiometrie waren auch Veränderungen in der Struktur der mikrobiellen Gemeinschaften verbunden. Deutliche positive Beziehungen existierten zwischen den saprotrophen Pilzen und den Protozoen. Die steigenden Mengen von Protozoen waren wiederrum mit sinkendem mikrobiellen N:P verbunden. Diese Muster weisen auf Veränderungen in den Bodennahrungsnetzten durch Landnutzungsänderungen hin. Sehr deutliche Abweichungen von globalen Mustern der C:N:P Stöchiometrie deuten darauf hin, dass der Landnutzungswandel signifikanten Einfluss auf die C:N:P Stöchiometrie ausübt. Der Landnutzungswandel beeinflusste auch die mikrobielle Biomasse, die Basalatmung, sowie die mikrobielle Aufnahme und Produktion von NH4-N im Boden. Dabei zeigten kombinierte Erklärungsansätze die adäquateren Beschreibungen der Muster. In den kombinierten Modellen zur Erklärung der mikrobiellen Biomasse und der mikrobiellen Leistungen überwogen Prädiktoren der mikrobiellen Ressourcen und der bodenchemischen Umwelt. Ein weiterer Schwerpunkt der Untersuchungen lag auf der Erfassung der Effekte des Land-nutzungswandels auf die Aktivität von extrazellulären Bodenenzymen. Bisher ist wenig darüber bekannt, welche Faktoren die katalytischen Eigenschaften steuern und beispielsweise, ob es Zusammenhänge zur mikrobiellen Gemeinschaftsstruktur gibt. Um diese Fragen näher zu beleuchten wurden sechs hydrolytische Enzyme basierend auf MUF-Substraten untersucht. Die mikrobielle Produktion von AP stand dabei in Zusammenhang mit dem niedrigen P-Status der untersuchten Böden. Das wurde besonders durch die hohe AP Produktion im Vergleich zu BG belegt. Im Allgemeinen konnten drei verschiedene Mechanismen festgestellt werden, die die Produktion der untersuchten EHEs vermutlich steuerten. 1.) Der P-Bedarf der Mikroorganismen regulierte die Produktion von AP, vorausgesetzt, dass ausreichend N und C zur Enzymsynthese zur Verfügung standen. 2.) Die Höhe der mikrobiellen Biomasse hat sich als wichtiger Faktor für die Produktion von CBH, BG und NAG gezeigt. Das deutet auf die konstitutive Produktion dieser Enzyme hin. 3.) Die substratinduzierte Produktion von Enzymen ist vermutlich entscheidend für die Aktivität von AG und XYL. Die Berücksichtigung der Enzymkinetiken, insbesondere der Michaelis-Menten-Konstante lieferte weitere Aufschlüsse über relevante Faktoren. Im Allgemeinen so scheint es, haben sich die mikrobiellen Gemeinschaften an die starken Umweltgradienten, die durch den Landnutzungswandel erzeugt worden angepasst. Im Vergleich zu den verfügbaren Daten aus Reinkulturen, wiesen die mikrobiellen Gemeinschaften der untersuchten Böden in der Regel eine deutlich höhere katalytische Effizienz auf. Auch für die Michaelis-Menten-Konstante sind die Faktoren enzymspezifisch. So ist für die Km von XYL der Boden-pH-Wert, für AP das C:N Verhältnis und für NAG die DOC-Menge entscheidend. Darüber hinaus haben sich deutliche Beziehungen zwischen der Menge an Gram(-)-Bakterien und der Substrataffinitäten von XYL und AP ergeben. Je höher die Gram(-)-Abundanz, desto höher war die Substrataffinität der Enzymsysteme. Gegenüber alter und degradierter Weiden, war der Umsatz der untersuchten Substrate im Oberboden der aktiv genutzten Weide drei- bis vierfach erhöht. In einem 5-jährigen Düngeexperiment in der Bergregenwaldregion der Anden Süd-Ecuadors wurden die Reaktionen des auf dieser Fläche N/P co-limitierten Grases (Setaria sphacelata), der Arbuskulären Mykorrhiza (AMF) sowie der Bodenmikroorganismen auf moderate N, P und N+P-Düngung untersucht. Die Zugabe von N+P erhöhte die oberirdische Biomasse (+61%) wohingegen die Wurzelbiomasse durch die Zugabe von P (+45%) anstieg. Die C:N:P Verhältnisse weisen auf veränderte P-Aufnahme oder Translokation von P in die Wurzeln hin. Im Besonderen verengte sich das Wurzel C:N and C:P in der P- und der N-Zugabe. Die aus dem Boden extrahierbaren C, N und P-Fraktionen wurden deutlich beeinflusst. Die Zugabe von P stimulierte die Biomasse Gram-(+)-Bakterien (+22%), die Abundanz der AMF (+46%) und die Brutto-N-Mineralisierung. Die Auswertungen deuten darauf hin, dass die Nährstoffanreicherung indirekt über die Veränderungen der Graswurzeln auf die Bodenorganismen wirkte. Die Ergebnisse bestätigen, dass N und P in den Reaktionen von co-limitierten Pflanzen eng miteinander verbunden sind. Vor allem aber steuert P grundlegend die Allokation von Ressourcen und wirkt damit auf andere Ökosystem-komponenten, z.B. auf die Struktur und Aktivität der Bodenmikroorganismen

Weathering releases lithogenic elements to soil and stream waters that support life in catchment ecosystems. Seasonal and inter-annual variations in hydrologic conditions change subsurface flowpaths, modifying the influence of weathering on stream waters. This study, over two climatically variable years, determined seasonal and inter-annual changes in solute sources to streams using a multi-tracer approach including major cations, strontium isotopes, germanium (Ge)/silica ratios, carbon species, and trace metals. Stream water cations display constant concentrations although discharge response was highly variable, suggesting that there is a consistent subsurface water supply. However, Sr isotope ratios, and concentrations of Ge, Fe, Al, and dissolved organic carbon, which originate from shallow soil waters, increase with the hydrograph during a wet winter snowmelt. This indicates that during a year with a thick snowpack, stream waters contain components of both shallow soilwater and groundwater during snowmelt, whereas during all other times groundwater contributes predominantly to the stream.

Dans le contexte actuel du changement climatique et de l’augmentation de la fréquence et de l’intensité des épisodes climatiques extrêmes, une question centrale pour l’écologie scientifique est de comprendre les répercussions de ces changements sur le fonctionnement des écosystèmes. Les communautés microbiennes du sol contrôlent une grande partie des processus écosystémiques déterminant la circulation de l’énergie et des nutriments. Dans le cadre des agroécosystèmes se pose donc la question de l’influence des pratiques agricoles sur les communautés microbiennes du sol et sur leur aptitude à maintenir le fonctionnement des écosystèmes face au changement climatique. L’intensification écologique de l’agriculture a récemment été proposée comme une approche intégrant les processus écologiques dans la stratégie de gestion des agroécosystèmes, dans l’objectif d’optimiser leur fonctionnement et leur résilience. L’écologie fonctionnelle pourrait répondre à certains des enjeux posés par le changement climatique et l’intensification écologique de l’agriculture.Dans cette thèse, j’ai cherché à mobiliser le cadre conceptuel des traits fonctionnels pour apporter de nouveaux éléments de compréhension de l’influence de différentes modalités d’intensité de gestion d’agroécosystèmes prairiaux (gestion extensive, conventionnelle-intensive et écologiquement-intensive) : 1) sur les caractéristiques fonctionnelles des communautés microbiennes du sol; 2) sur la capacité de ces communautés microbiennes à maintenir le fonctionnement de l’écosystème face à des périodes de stress climatiques (résilience). Dans le cadre de ma thèse, trois expérimentations ont été réalisées en faisant varier le degré de contrôle des facteurs de gestion, le type de stress climatique et la durée de ces stress. S’appuyant sur des agroécosystèmes prairiaux répartis dans trois pays Européens (France, Suisse, Portugal), les résultats des deux premières expérimentations de cette thèse montrent que les communautés microbiennes des sols des prairies écologiquement-intensives disposent d’une plus faible capacité à maintenir les propriétés écosystémiques microbiennes durant les stress (faible résistance) mais disposent d’une meilleure capacité de récupération comparée aux communautés microbiennes des sols en gestion conventionnelle-intensive. Une autre étude montre que la gestion éco-intensive favorise des communautés microbiennes protéolytiques bénéfiques à l’assimilation de l’azote pour les plantes en conditions perturbés. L’étude des traits végétaux suggère que ces effets de la gestion sur la composition des communautés microbiennes et sur leur résilience passe par certains traits, notamment une augmentation de la richesse en phosphore des litières en gestion écologiquement-intensive. En effet ces traits fonctionnels des plantes semblent influencer les traits microbiens, favorisant des communautés microbiennes copiotrophes, caractérisées par un ratio azote:phospore faible de leur biomasse et un faible investissement dans la production d’enzymes extracellulaires, deux traits négatifs pour la résistance au stress mais favorisant une récupération rapide. Ainsi, ces deux expérimentations soulignent l’importance de la gestion des traits des plantes dans le contrôle des traits microbiens et de la résilience des écosystèmes au changement climatique. La troisième expérimentation a cherché à tester spécifiquement les effets d’un épisode de fertilisation minérale sur la résilience des communautés microbiennes à différents stress climatiques. Les résultats montrent que la fertilisation modifie la composition et les traits microbiens avec des répercussions négatives sur la stabilité de l’écosystème face à la sécheresse et à l’inondation.Mobilisant une approche par le concept de trait fonctionnel microbien, ce travail de thèse apporte de nouveaux éléments de compréhension des effets de l’intensité de gestion sur la résilience des écosystèmes prairiaux face aux stress climatiques
In the current context of climate change, associated with increases of climate extremes frequency and intensity, understanding the ecosystem response to climate variability is a central challenge in ecology. Soil microbial communities control most ecosystem processes driving energy and nutrients fluxes. In the context of agriculture management, an important question is to understand the influence of farming practices on soil microbial communities and their capacity to maintain ecosystem functioning under climate change. Ecological-intensive agriculture has been recently proposed as an approach integrating ecological processes in management strategies to optimise agroecosystems functioning and resilience to climate change. Functional ecology might be relevant to address these challenges associated with climate change and ecological-intensification of agriculture.In this PhD thesis, I used the functional trait framework to grassland ecosystems to address how different modalities of management intensity (extensive, conventional-intensive, ecological-intensive management) influence: 1) functional parameters of soil microbial communities; 2) the capacity of these soil microbial communities to maintain ecosystem functioning during and after climatic stresses (Resilience). During my PhD, three experiments have been conducted using different degrees of control of management factors and simulating different kind of climatic stresses, with different durations. Based on grassland agroecosystems in three countries across Europe (France, Switzerland, Portugal), results from the first two experiments of this PhD showed that ecological-intensive management select soil microbial communities with a lower capacity to maintain microbial ecosystem properties during stresses (resistance) but with higher capacity to recover compared with soil microbial communities of soils under conventional-intensive management. Moreover, another study showed that ecological-intensive management promotes beneficial proteolytic soil microbial communities for plant nitrogen uptake under climate change-induced rain regimes. Plant functional traits assessment suggest this management effect on microbial communities composition and resilience to be explained by higher litter phosphorous content in ecological-intensive systems. Indeed, this plant functional trait affect microbial traits, favouring copiotrophic microbial community characterized by a lower nitrogen:phosphorous ratio of their biomass and a lower investment in extracellular enzymes production, two traits decreasing stress resistance but increasing recovery capacities. Thereby, these two experiments stress the relevance of plant traits management to control soil microbial traits and the resilience of soil microbial communities to climate changes. A third experiment tested specifically the impact of a mineral fertilisation event on the resilience of soil microbial communities to different climatic stresses. Results clearly demonstrated that fertilization modify soil microbial community composition and soil microbial traits and decrease ecosystem stability under climatic stresses.Implementing an approach based on the microbial functional trait concept, this thesis brings new insights on the effects of management intensity on grassland ecosystem resilience to climatic stress

Limited information is available on carbon(C)sequestered in frigid Appalachian forest soils. However,the cool moist forests of the high elevations probably hold more C than any other mineral soils in Virginia. The objectives of the study were to determine the amount and variability of soil C across aspect and slope classes in a frigid temperature regime area of Tazewell County, VA. Soils were sampled to characterize two aspect classes, N(340-90º) and S (160-270º), and three slope classes, 7-15%, 15-35%, 35-55%. Organic (L,F,H) and mineral layers and horizons (upper 5cm, A, B) were sampled at each site. Whole soil (including organic and mineral horizons) C contents on N aspects (135 Mg/ ha) were greater than on south aspects (107 Mg/ha). Average whole soil C across all sites was 112 Mg ha-1. The A horizons on N aspects (13cm) were deeper than those of the S aspects (8 cm), while average leaf litter weights were greater on the S aspects (25 Mg/ ha) versus the N (17 Mg/ ha). B horizon C was greater than 1.5 % and made up more than half of the total soil C. Carbon increased with slope on N aspects, but did not increase with slope on S aspects, because estimated solar insolation potential decreases with increasing slope on N aspects and has no trend on S-facing slopes. Total C appears to be greatest on steep N-facing slopes because cooler and moister conditions promote better mixing of organic material into the mineral soil.
Master of Science

Chemical input-output analyses were used to evaluate the rate of rock weathering and soil development on a granitic inselberg of the Dragoon Mountains in southeastern Arizona. Soil genesis relationships were investigated through field and laboratory study of the soil profile, parent rock, microclimate and vegetation, on different catena positions and hillside aspects. Precipitation and runoff water qualities were determined, with increased summer acidity. Precipitation volume was estimated by extrapolating data from a nearby recording station. Runoff volume was estimated by the U.S.D.A.-S.C.S. Curve Number Method (1972). These data enabled the quantitative determination of cationic solution loss. The indicated decreasing order of cation mobility is calcium, sodium, potassium and magnesium. Cations of higher mobility are relatively depleted in the hillcrest soils, while transported to the footslope or beyond. Calcium, and to a lesser extent sodium, have experienced more extensive off-site removal. Differences resulting from the transformation of parent material to soil were analyzed by field morphology, X-ray analysis, laser light-scattering particle size analysis, and chemical analyses. The study site was surveyed, mapped and the spatial arrangement of soil taxa and their compositional variation were studied. Nearly all pedons on the crest or transport slope are Lithic Ustic Torriorthents; whereas footslope soils show greater development, as exemplified by the occurrence of various Haplargids, Haplustolls and Argiustolls. Weathering rates were calculated using a methodology similar to that of F. W. Barth (1961). Potassium and magnesium provided the most reasonable data of 350 and 430 Kg ha⁻¹ yr⁻¹, respectively. (equivalent to 13.5 and 16.5 mm of rock weathered per 1000 years). Two serrated projectile points were found inbedded on the clayey soil surface of an adjacent ancient pond site. These artifacts resemble another projectile point found in southeastern Arizona which has been radiocarbon dated ~7,000 yr B.P. A minimum age for the pond and immediate surrounding topography is suggested to correspond with the end of the western subhumid pluvial period. The assessment of the geochemical budget provided a valuable framework for quantification of the various processes which interactively determine the rates of weathering and soil formation.

Mountainous regions comprise more than 30% of the world's terrestrial biomes and are valued for livestock forage, mineral and timber assets and recreation opportunities. Disturbance has resulted in major ecological changes in high elevation ecosystems, including vegetation loss, soil compaction, and reduced soil organic matter (SOM). Restoring high elevation disturbed sites has proven challenging for many years, possibly because of our limited knowledge of disturbance effects on belowground biota, and the ecosystem functions they facilitate. This research compares soil physiochemical and biological properties on disturbed, undisturbed and restored subalpine soils in two national forests in Montana and Washington. Soil physiochemical properties measured include soil moisture, bulk density, SOM, soil nitrogen (N; both total and plant available), phosphorous (P) and potassium (K). Biological processes measured include mycorrhizal infectivity potential (MIP), decomposition, enzyme activity, substrate induced respiration (SIR) and N mineralization. Soil moisture and SOM were significantly lower, while bulk density was higher, on disturbed sites. Total nitrogen (N) was lower on disturbed sites, while NO₃ - and NH₄ + differed only between geographic locations. MIP was low overall and did not differ between disturbance. Decomposition rates did not differ between disturbance after 3, 12 or 24 months. Enzyme activity differed with disturbance and location, with significantly lower activity on disturbed sites for 1 substrate, while nearly significant lower activities for 4 out of 8 substrates measured. SIR differed with disturbance and location, with lower responses on disturbed sites for 6 of 26 substrates. Soil physiochemical and biological characteristics are affected by disturbance and location, however results vary between the parameters measured. This suggests ecosystem components, including soil physiochemical and biological properties are decoupled, responding individualistically to disturbance and restoration.

Fuel accumulation rate and total soil nitrogen, phosphorus, and sulfur following prescribed fires were studied. Three prescribed fires were conducted in S.E. Arizona ponderosa pine stands during the summers of 1979, 1980, and 1981. Samples of forest floor and larger diameter fuel and soil from the surface 1.5 inches and 1.5 to 3.0 inch layers were collected in the summer of 1981. Forest floor and total fuel accumulation averaged 5.4 to 6.7 and 6.3 to 8.9 tons/acre/year, respectively. Total nitrogen, phosphorus, and sulfur in the surface three inches of mineral soil were not significantly affected by burning. Soil nitrogen, phosphorus, and sulfur content averaged 0.21%, 344 ppm and 150 ppm, respectively, in the surface 1.5 inches and 0.11%, 285 ppm and 74 ppm, respectively, in the 1.5 to 3.0 inch layer.

The objectives of this study were two fold. The first was to quantify the nature and extent of current levels of human impact in alpine areas at four sites within Fiordland and Mount Aspiring National Parks along walking tracks at Key Summit, Gertrude Saddle, Borland Saddle and Sugarloaf Pass. In order to do so, a survey was carried out with transects placed perpendicular to the track, and distributed among different vegetation types. In each transect, plant structural and compositional aspects, and soil and environmental parameters were measured. Transects were divided into track, transition, undisturbed and control zones, and changes to dependent variables were compared with distance from the track centre. Damage from visitor impact was largely restricted to within 1m from the track centre. The most significant impacts were to structural aspects of plant and soil properties with significant reductions in plant height, total vegetation cover and bryophyte cover, and increases in bareground and erosion on tracks. Erosion was more prevalent on slopes greater than 25°, while tracks on peat soils contained greater bareground exposure, particularly of organic soil. The second study objective was to investigate the relationship between specific levels of impact and the resulting damage to two key alpine vegetation types, tussock herb field and cushion bog. This was undertaken by carrying out controlled trampling experiments, measuring changes to plant structural and compositional aspects four weeks and one year after treatment. Both vegetation types saw dramatic reductions in total vegetation cover and height immediately after trampling, however overall composition and species richness varied little. These two alpine vegetation types showed moderate-low resistance to initial impact and low resilience, with very little recovery evident one year later. Research intothese two areas is important for managing visitor use within alpine areas in order to meet conservation and recreation goals. The survey indicates that alpine community types are very sensitive to visitor use, showing significant structural damage, however the spatial extent of impact is limited within the broader landscape. Instead, visitor impacts associated with tracks are likely to be more visually and aesthetically significant, influencing the visitor experience. The trampling experiments indicate that use levels over 25-75 passes per year within tussock herbfield and cushion bog vegetation on peat soils will result in ongoing damage to previously undisturbed sites. Methods for minimising impacts include limiting visitor numbers, public education in low impact practices, redirection of tracks and use to areas that are less sensitive, the dispersal of visitor activity at very low use intensities (less than 75 direct passes per year) and the concentration of activity on tracks above this level.

Kyoto University (京都大学)
0048
新制・課程博士
博士(農学)
甲第10235号
農博第1307号
新制||農||862(附属図書館)
学位論文||H15||N3756(農学部図書室)
UT51-2003-H656
京都大学大学院農学研究科森林科学専攻
(主査)教授 水山 高久, 教授 野渕 正, 教授 谷 誠
学位規則第4条第1項該当

Soils darken upon wetting due to changes in the scattering properties of the individual soil particles. The objective of this research was to develop a procedure to map the distribution of wet soils using the radiance measurements acquired by a spaceborne imaging scanner. The soil-mapping procedure was designed for use in the regional exploration for ground water resources. The soil-mapping procedure was based upon the detection of reflectance changes in a comparison of Landsat 5 Thematic Mapper (TM) scenes acquired before and after a rain. The Stronghold watershed, which is situated on the western slopes of the Dragoon Mountains, Cochise County, Arizona, was chosen as the test site for the soil-mapping procedure. TM scenes depicting the watershed on 7 June 1985 and 14 November 1985 were used in the change-detection analysis. The region was dry at the time of the June overpass, the November overpass occurred two days after a rain. The recovery of reflectance from radiance requires knowledge of 1) the orientation of the surface relative to the sun and the satellite, 2) the exoatmospheric solar irradiance, 3) the atmospheric optical depth, and 4) the atmospheric path radiance. The orientation of the surface elements were defined through the use of a digital elevation model of the Stronghold watershed. The solar irradiance and atmospheric optical depth were obtained from the literature; the atmospheric path radiance was estimated from shadowed areas depicted in the images. Temporal changes in reflectance were detected by subtracting the November reflectance estimates from those recovered from the June radiance measurements. Changes significant at the 0.05 level were identified through use of the Student-t test. The identical significance level was used to identify temporal changes in the Perpendicular Vegetation Index, or PVI. A surface element was classified as an anomaly if there was a significant temporal change in reflectance with no attendant change in PVI. Field checks of the anomalies proved that wet soils could be mapped via the remote detection of changes in their reflectance. The majority of the false anomalies could be attributed to the disparity between the spatial resolutions of the radiance measurements and the topographic data.

Em função da ocorrência de desastres naturais no Brasil, instaurou-se em 2012 a Lei Federal no 12.608 de Política Nacional de Proteção e Defesa Civil, que incentiva medidas de previsão para conter desastres naturais e situações de risco. O uso de modelos matemáticos em bases físicas pode ser uma importante ferramenta no auxílio à redução das situações negativas geradas por escorregamentos, sobretudo em áreas íngremes como a Serra do Mar. O objetivo deste trabalho foi comparar cenários de suscetibilidade a escorregamentos translacionais rasos gerados pelo modelo TRIGRS na Bacia do Rio Guaxinduba (Caraguatatuba, SP) afetada por vários escorregamentos e corridas de detritos em março de 1967. Especificamente, objetivou-se gerar três cenários de suscetibilidade considerando valores da literatura, coletados in situ e distribuídos estatisticamente; caracterizar espacialmente as propriedades geotécnicas e hidrológicas do solo (coesão; densidade; espessura máxima; ângulo de atrito interno e condutividade hidráulica saturada vertical) coletadas in situ e avaliar a variação do Fator de Segurança (FS) conforme a profundidade do solo. Para isso, foram gerados três cenários utilizando-se, no primeiro, valores geotécnicos e hidrológicos disponíveis na literatura, no segundo, valores coletados dentro da bacia e no terceiro, valores geoestatisticamente distribuídos. A partir da combinação com o mapa de cicatrizes de 1967, para validação dos cenários foram utilizados os seguintes índices: (a) Concentração de Cicatrizes; (b) Potencial de Escorregamentos e (c) percentual de áreas instáveis sem cicatrizes e de áreas estáveis com cicatrizes. Os resultados dos cenários indicaram que o uso de dados geotécnicos e hidrológicos coletados in situ forneceu resultados melhores e mais representativos. Nos três cenários foi verificada uma concordância entre as cicatrizes e as áreas instáveis, mas houve uma diferença na distribuição de classes de estabilidade. Topograficamente, foram observadas maiores instabilidades em ângulos da encosta >20º, com formas retilíneas e côncavas e em classes intermediárias de área de contribuição. Geotecnicamente, foram observadas importantes relações entre a instabilidade e os valores de coesão do solo; especialmente entre os valores de 0kPa a 6kPa. Nos demais parâmetros, observou-se maior suscetibilidade nas áreas com densidade entre 17kg/m3 e 18kg/m3; espessuras de 3m; ângulos de atrito interno entre 31º e 35º e condutividade hidráulica entre 1,0x10-3m/s e 1,0x10-4m/s. Em função dos resultados obtidos, o modelo TRIGRS e a espacialização de parâmetros geotécnicos e hidrológicos podem ser utilizados pelo poder público, em suas diferentes esferas administrativas para a definição de áreas de risco e para o planejamento do uso e ocupação do solo (ex. construção de moradias e de estradas, práticas florestais, entre outros).
Due to the occurrence of natural disasters in Brazil, the National Protection and Civil Defense Policy Federal Law no. 12,608 was established in 2012, which encourages prediction measures to minimize natural disasters and risk situations. The use of mathematical models in physical basis can be an important tool in helping to reduce negative situations generated by landslides, especially in steep areas such as the Serra do Mar mountain rage. The goal of this work was to compare susceptibility scenarios to shallow landslides generated by the TRIGRS model at the Guaxinduba hydrographic basin (Caraguatatuba, SP), affected by various landslides and debris flows in March 1967. Specifically, the generation of three susceptibility scenarios was aimed, considering literature values, collected in situ and statistically distributed; to spatially characterize the geotechnical and hydrological properties of the soil (soil cohesion; soil density; soil thickness; internal friction angle and saturated hydraulic conductivity) collected in situ and evaluate the Factor of Safety (FS) according to soil depth. To achieve this, three scenarios were generated, using, in the first, geotechnical and hydrological values available in literature, in the second, values collected inside the basin and in the third, geostatistically distributed values. From the match with the 1967 map of scars, the following indexes were used to validate the scenarios: (a) Scars Concentration; (b) Potential Landslides and (c) percentage of unstable areas without scars and stable areas with scars. The results of the scenarios indicated that the use of in situ collected geotechnical and hydrological data supplied better and more representative results. In the three scenarios, a concordance between the scars and the unstable areas was verified, but there was a difference in the distribution of stability classes. Topographically, greater instabilities were observed at >20º slope angles, with slope straight and concave slope shapes, and at intermediate classes of contribution area. Geotechnically, important relations between the instability and the soil cohesion values were noted; especially between the values ranging from 0kPa to 6kPa. In the other parameters, a greater susceptibility was observed in the areas with densities between 17kg/m3 and 18kg/m3; 3m thicknesses; internal friction angles between 31º and 35º and hydraulic conductivity between 1,0x10-3m/s and 1,0x10-4m/s. According to the results, the TRIGRS model and the spatialization of geotechnical and hydrological parameters may be used by the Government, in its various administrative levels, for the definition of risk areas and to plan the land use and occupation (e.g., construction of housing and roads, forest practices, among others).

Malgré des accidents réguliers, la moyenne montagne n’occupe qu’une place mineure dans l’étude des avalanches. Cette thèse vise donc, par une approche interdisciplinaire, à analyser la réalité du risque d’avalanche dans le Massif vosgien. Considérant le risque comme un construit social, on se propose d’appréhender les cultures du risque d’avalanche, puis d’étudier sa réalité matérielle (approche diachronique, spatialisation, conditions d’occurrence et d’émergence du risque).Pour déterminer s’il existe reconnaissance et appropriation du risque d’avalanche par les acteurs participant au processus de construction du risque, on a procédé à une analyse de discours des différents acteurs intervenant dans sa gestion et à des enquêtes, l’une inductive par entretiens, l’autre par questionnaire. In fine, d’une manière générale, connaissances et mémoire collective font défaut et, quelle que soit l’échelle, le risque d’avalanche n’est pas identifié en tant que problème. Il est au mieux désigné comme un danger ponctuel et localisé auquel on se sent peu vulnérable. Parallèlement, à travers une démarche géohistorique, on a étudié l’inscription spatiale et temporelle des avalanches sur les deux derniers siècles et cherché à identifier les facteurs naturels et sociaux interagissant dans le système de production du risque. Il apparait que, si la connaissance des avalanches est dépendante des sources, leur dynamique est fortement conditionnée par les activités anthropiques passées et actuelles. Malgré la fréquence des avalanches, ce risque n’apparait pas comme un élément fondamental des cultures montagne dans le Massif vosgien et nécessite un travail d’information et de sensibilisation
In spite of regular accidents, the medium-high mountain doesn’t seem to play a major role in the study of avalanche. Therefore, the main goal of this thesis is to emphasize the reality of the avalanche risk in the Vosges Mountains by an interdisciplinary approach. Considering risk itself as a social construction, we suggest to study at first the cultures of avalanche risk and then pursue with its material reality (diachronic approach, spatialization, risk occurrence and conditions of emergence). So as to establish if the different protagonists involved in the process of risk construction recognize and appropriate the avalanche risk, we have analyzed the statements of the persons in charge of those events and conducted two different surveys (inductive interviews and a questionnaire). In the end, there is a lack of knowledge and collective memory, and the risk of avalanche seems not to be considered and identified as a real problem. At the very best, it is pointed out as an occasional and localized danger, to which people do not really feel vulnerable.At the same time, through a geo-historical approach, we studied the spatial and temporal distribution of avalanches over the last two centuries and tried to identify the natural and social factors interacting in the risk production system. It appears that, if knowledge concerning avalanches is based on historical sources, their dynamic is strongly conditioned by past and current human activities. Despite the frequency of avalanches, this risk does not appear as a fundamental element of the mountain cultures in the Vosges range and requires measures to draw the attention of people and inform them about it

Dans le contexte d'augmentation de la pression démographique et des risques liés aux changements climatiques, la question de l'érosion est de plus en plus cruciale. La gestion actuelle des milieux des montagnes méditerranéennes, particulièrement affectés par ces phénomènes, repose sur une bonne connaissance de leurs sensibilités à l'érosion et de leurs trajectoires à long terme. Une approche rétrospective des trajectoires des environnements a été menée par l'étude de trois archives sédimentaires lacustres prélevées dans les Alpes du Sud (lacs Petit, Vens et Allos). L'étude multidisciplinaire (sédimentologie, géochimie, palynologie) a permis de caractériser les dynamiques érosives et végétales depuis 14000 ans. À Allos et Vens, le début de l'Holocène est marqué par la maturation des écosystèmes, l'altération chimique des sols et la progression altitudinale des forêts. Ces dynamiques environnementales conduisent à la stabilisation progressive des écosystèmes, suivie d'un optimum bio-pédologique, d'une ouverture des paysages et d'une déstabilisation des sols respectivement datées de 12000-8000 cal. BP, 8000-6000 cal. BP, 6000-1900 cal. BP et de 1900 cal.BP à aujourd'hui. Cette dernière période de déstabilisation des sols intervient plus tôt au Lac Petit, à 4200 cal. BP.Les dénominateurs communs au déclenchement de l'érosion sont à chaque fois une période de précipitations fréquentes sur un milieu fragilisé : l'impact des sociétés a provoqué un abaissement du seuil de sensibilité des milieux aux perturbations, particulièrement à l'agressivité des précipitations
Within the context of increasing demographic pressures and hazards related to climate change, the problems posed by landscape erosion have become particularly crucial. The current management of Mediterranean mountain environments, which are highly exposed to erosion hazards, needs to be supported by a thorough understanding of their susceptibility to these hazards and their long-term trajectories.A retrospective analysis of environmental trajectories has been conducted from the study of three lacustrine sedimentary archives in the Southern Alps (Lakes Petit, Vens and Allos). This multi-disciplinary study, based on sedimentology, geochemistry and palynology, has enabled characterization of the dynamics of erosion and changes in plant cover over the last 14,000 years.In Lakes Allos and Vens, the start of the Holocene is marked by the maturing of ecosystems, by chemical weathering of soils and by forest encroachment at higher altitudes. These environmental changes resulted in progressive ecosystem stabilization, followed by a bio-pedological optimum, and subsequently by more open landscapes, and then soil destabilization. These four successive phases have ben dated, respectively, at 12,000-8000 cal. BP, 8000-6000 cal. BP, 6000-1900 cal. BP, and 1900 cal. BP to Present. The last of these phases occurred earlier, at 4200 cal. BP, in Lake Petit.The triggering of soil erosion has systematically been hinged on periods of heavy precipitation affecting landscapes rendered vulnerable, by human societies, to the effects of such perturbations

The quantification and prediction of soil properties is fundamental to further understanding the Critical Zone (CZ). In this study we aim to quantify and predict soil properties within a forested catchment, Marshall Gulch, AZ. Input layers of soil depth (modeled), slope, Saga wetness index, remotely sensed normalized difference vegetation index (NDVI) and national agriculture imagery program (NAIP) bands 3/2 were determined to account for 95% of landscape variance and used as model predictors. Target variables including soil depth (cm), carbon (kg/m²), clay (%), Na flux (kg/m ²), pH, and strain are predicted using multivariate linear step-wise regression models. Our results show strong correlations of soil properties with the drainage systems in the MG catchment. We observe deeper soils, higher clay content, higher carbon content, and more Na loss within the drainages of the catchment in contrast to the adjacent slopes and ridgelines.