Dissertations / Theses on the topic 'Mountain plants'

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.

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.

Thesis (Ph.D.) -- La Trobe University, 2007.
Research. "A thesis submitted in total fulfillment of the requirements for the degree of Doctor of Philosophy, Department of Botany, School of Life Sciences, Faculty of Science, Technology and Engineering, La Trobe University, Bundoora". Includes bibliographical references (leaves 173-187). Also available via the World Wide Web.

Proglacial environments, formed by glacier retreat, exhibit distinct characteristics in discharge, water temperature, water residence time, and dissolved ion, carbon, and suspended sediment concentrations. The unnamed alpine glacier at the headwaters of the Wheaton River, Yukon, Canada, provides an ideal setting to compare deglaciation processes that result in three different proglacial environments. The glacier has evolved from occupying one large catchment (~4 km 2) to two smaller catchments (each ~2 km 2) via glacier thinning and net mass loss, forming two lobes separated by a medial moraine. Field observations revealed neither crevasses nor evidence of subglacial drainage outlets and suggested this glacier had a non-temperate thermal regime with meltwater predominantly flowing from supraglacial and ice marginal sources. Climate and bedrock geology were similar for the subcatchments, providing a natural laboratory to compare deglaciation processes. This study compared the hydrology and biogeochemistry of three outlet streams from this glacier: one stream drained a proglacial lake which is fed by meltwater from the lower west lobe, a second stream drained the upper west lobe, and a third stream was the major drainage outlet for the east lobe. Hydrologic monitoring over the 2006 melt season (June-August) and analyses of water samples for dissolved ion content and carbon indicated that the meltwaters are dominated by Ca 2+ and HCO 3-, which are derived from biogeochemical weathering of crustal materials. The study demonstrated that the presence of the proglacial lake, which acted as a meltwater reservoir, measurably modified meltwater residence time, water temperature, water chemistry, and bacterial biomass relative to the proglacial streams. Rock:water interaction between meltwater and medial morainal sediment and fine-grained, reactive glacial flour suspended in the streams and the lake water column also enhanced biogeochemical weathering within the catchment. Thus, this study provided a small-scale example for how differences in proglacial environments and water flow paths affect headwater hydrology and biogeochemistry. This study was the first of its kind in the Coast Mountains, Yukon, Canada, and results presented here aid in the understanding of how proglacial environments created by climate-induced glacier retreat affect hydrochemistry, hydrology, and carbon dynamics in remote high elevation environments.

Botanical exploration in northern British Columbia has lagged behind that of adjacent Alaska and the Yukon Territories. This is particularly true of alpine and sub-alpine areas. For the most part, limited accessibility has restricted plant collecting to within a short distance of the few available roadways. During the course of the present study, botanical field work was conducted in an alpine, sub-alpine area in the Three Sisters Range of the Cassiar Mountains (northwestern British Columbia). Over 1000 vascular plant collections were idenified from the study area. A total of 239 Taxa were recognized representing 116 genera and 44 families. Taxonomic keys to the local flora and an annotated species list are provided. The annotated species list includes : habitat information for each taxon, a list of associated species and, where applicable, a discussion of noteworthy features of the taxon in question. Approximately 13% of the flora examined is listed as rare in British Columbia in Straley et al. (1985). Virtually all of northern British Columbia was overridden by the Cordilleran Ice Sheet during the last major Wisconsin advance (approximately 22,000-15,000 yrs. b.p.). Potential Refugia from which taxa now present in the study area may have migrated post-glacially are discussed. Worldwide distributions of each taxon were examined and seven phytogeographic elements are recognized in the flora.
Science, Faculty of
Botany, Department of
Graduate

This study is an interdisciplinary ecological study addressing the fine-scale relationships between plants, invertebrates and the environment in an alpine ecosystem. Alpine environments are marked by steep environmental gradients and complex habitat mosaics at various spatial scales. Regular forming periglacial patterned ground landforms on the Old Man Range, Central Otago, South Island, New Zealand present an ideal medium for studying plant-invertebrate-environment relationships due to their partitioning of the landscape into discrete units of contrasting environmental conditions, and the existence of some baseline knowledge of the soil, microclimate, vegetation and flora. The study was conducted in three types of patterned ground (hummocks, stripes and solifluction terraces) on the Old Man Range. Each component of the study was sampled at the same spatial scale for comparison. Temperature was recorded in the soil and ground surface from April 2001 to March 2004 in microtopographic subunits (microsites) of each patterned ground landform. Plant species cover was sampled within each microsite; invertebrates were sampled from soil cores taken from the same locations as plant samples in April 2001 and September 2001. The two sampling occasions coincided with autumn before the soil freezes, and winter when maximum freezing was expected. Fine-scale changes in the topographic relief of the patterned ground led to notable differences in the timing and duration of snow. The steepest environmental gradients existed during periods of uneven snow distribution. The soil in exposed or south-facing microsites froze first, beginning in May, and typically froze to more than 40cm depth. Least exposed microsites rarely froze. Within the microtopography, patterns of freezing at specific locations were consistent between years with only minor differences in the timing or depths of freezing; however, notable variation in freezing existed between similar microsites. Within the microtopography, different assemblages of organisms were associated with different microsites. In total, 84 plant and lichen species were recorded, grouping into six community types. Species composition was best explained by growing degree-days, freeze-thaw cycles, time frozen and snow-free days; species diversity and richness increased with increasing environmental stress as indicated by freeze-thaw cycles, time frozen and exposure. In total 20,494 invertebrates, representing four Phyla, 12 Classes, 23 Orders and 295 morpho-taxa were collected from 0.17m� of soil. Acari, Collembola and Pseudococcidae were the most abundant invertebrates. Over 95% of the invertebrates were found in the plant material and first 10cm depth of soil. Few significant relationships were found between diversity, richness or abundance of invertebrate taxa and the microsites; however, multivariate analyses identified distinct invertebrate assemblages based on abundance. Invertebrate composition was best explained by recent low temperature and moisture, particularly in winter; however, plant composition also explained invertebrate composition, but more so in autumn. This research has shown that organisms in the alpine environment of the Old Man Range are sensitive to fine-scale changes in their environment. These results have implications as to how historical changes to the ecosystem may have had long-lasting influences on the biota, as well as how a currently changing climate may have further impacts on the composition and distribution of organisms.

High-elevation and high-latitude ecosystems are expected to be especially vulnerable to global change. Dwarf shrub species cover extensive areas in high mountain ecosystems, and warmer temperatures and land-use change have favoured their expansion. Co-occurring dwarf shrub species may respond differently to climate change, which can have major effects on their interactions, growth and performance, and ultimately lead to drastic changes in plant communities. In this Thesis, warming, CO2 enrichment and drought experiments have been carried out at the ecotone between the subalpine and alpine belts in different study sites across the Pyrenees and the Alps. The objective was to assess how these factors may influence dwarf shrub species interactions, growth, xylem anatomy and C allocation dynamics. Results of this Thesis show species-specific responses to the treatments, and these responses differed in magnitude and direction depending on the treatment applied. Vaccinium myrtillus responded positively to increased temperatures, whereas the co-occurring Vaccinium uliginosum and Empetrum hermaphroditum showed no response. Vaccinium myrtillus growth and functioning was similar across stands differing in neighbouring shrub species and we did not find evidence of alterations in plant-plant interactions with warming. Vaccinium myrtillus responded positively to CO2 enrichment with an increased stem basal area and a lagged increased vessel lumen size and xylem-specific hydraulic conductivity, but hydraulic efficiency decreased with warming. Although there was a correlation between growth and accumulated hydraulic conductivity, the growth-anatomical relationship changed with soil warming and CO2 enrichment, and growth stimulation occurred without immediate accompanying changes in the xylem anatomy. We did not find major effects of the experimental summer drought on V. myrtillus water potential and its allocation of recently assimilated C. However, V. uliginosum showed evidence of mild stress, since its stomatal conductance, water potential and speed of C transfer to belowground organs were reduced under drought. All these results suggest that climate change acts differently on co-occurring species, which may lead to future changes in plant community composition, structure and function.
Els ecosistemes d'elevades altituds i latituds són especialment vulnerables al canvi global. Les espècies subarbustives poden cobrir àrees extenses en zones d'alta muntanya, i l'augment de la temperatura i els canvis en l'ús del sòl n'afavoreixen l'expansió. Les espècies subarbustives que coexisteixen podrien respondre de manera diferent al canvi climàtic, cosa que podria tenir grans efectes en les seves interaccions, així com en el seu creixement i el seu funcionament i, en última instància, comportar canvis dràstics en les comunitats vegetals. En aquesta Tesi Doctoral s'han dut a terme experiments d'escalfament, d’augment de la concentració de CO2 de l’aire i de sequera a l'ecotò entre els estatges subalpí i alpí en diferents zones del Pirineu i dels Alps. L'objectiu era comprendre com aquests factors afecten les interaccions entre espècies subarbustives, el seu creixement, l’anatomia del xilema i la distribució de carboni (C). Els resultats d'aquesta Tesi mostren respostes específiques als tractaments. A més, aquestes respostes diferien en magnitud i direcció en funció del tractament aplicat. Vaccinium myrtillus va respondre positivament a l'escalfament, mentre que les espècies coexistents Vaccinium uliginosum i Empetrum hermaphroditum no van mostrar cap resposta. El creixement i funcionament de V. myrtillus era similar en claps amb diferent composició d'espècies arbustives i, contràriament al resultat de nombrosos estudis previs, no es van trobar evidències d'alteracions en les interaccions planta-planta amb l'escalfament. Vaccinium myrtillus va respondre positivament a l'augment de CO2 amb un augment de l'àrea basal i un augment retardat en la mida dels vasos conductors i la conductivitat hidràulica específica. Tanmateix, l'eficiència hidràulica es va reduir amb l'escalfament. Tot i que es va trobar una correlació entre el creixement i l’anatomia en termes de conductivitat hidràulica acumulada en V. myrtillus, aquesta relació va canviar amb els tractaments d'escalfament i augment de CO2, i el creixement va augmentar sota aquests tractaments sense que es produïssin canvis immediats en l'anatomia del xilema que l'acompanyessin. La sequera experimental no va tenir grans efectes en el potencial hídric ni en la distribució de C recentment assimilat de V. myrtillus. Tanmateix, V. uliginosum va presentar lleugers signes d'estrès amb la sequera, ja que la seva conductància estomàtica i el seu potencial hídric es van veure reduïts, així com també la velocitat de transferència de C cap a òrgans subterranis. Tots aquests resultats suggereixen que el canvi climàtic actua de diferent manera sobre espècies coexistents, cosa que podria comportar canvis en la composició de les comunitats, així com en la seva estructura i funcionament en el futur.

Dissertation (PhD)--University of Stellenbosch, 2003.
ENGLISH ABSTRACT: Riparian vegetation has received a lot of attention in South Africa recently, mainly because of its importance in bank stabilization and its influence on flood regimes and water conservation. The upper reaches have thus far received the least of this attention because of their inaccessibility. This study mainly focuses on these reaches where riparian vegetation is still mostly in a pristine state. The study area chosen for this purpose is the Hottentots Holland Mountains in the Southwestern Cape, the area with the highest rainfall in the Cape Floristic Region, which is very rich in species. Five rivers originate in this area and the vegetation described around them covers a large range of habitats, from high to low altitude, with different geological substrates and different rainfall regimes. All of these rivers are heavily disturbed in their lower reaches but are still relatively pristine in their upper reaches. All of them are dammed in at least one place, except for the Lourens River. An Interbasin Transfer Scheme connects the Eerste-, Berg- and Riviersonderend Rivers. The water of this scheme is stored mainly in Theewaterskloof Dam. Another big dam for water storage, Skuifraam Dam, will be built on the Berg River near Franschhoek in the nearby future. In order to study the vegetation around a river, a zonation pattern on the river bank is described and several physical habitats are recognized. A primary distinction is made between a Wet Bank (flooding at least once a year) and a Dry Bank (flooding less than once a year). The Dry Bank is further subdivided into a Lower Dynamic, a Shrub/Tree and a Back Dynamic Zone. In the lower reaches these zones are very distinct, but in the upper reaches of a river they tend to blend into each other and some zones can be absent or very narrow. Vegetation has been sampled in transects across the riverbed, following the Braun-Blanquet method. Additional vegetation samples have been recorded in the bogs and mires at the sources of the rivers. Vegetation structure and physical habitat has been described to contribute to the description of the vegetation types. In order to understand the environmental processes that determine the vegetation, environmental parameters were recorded in every vegetation sample, such as, slope, aspect, rockiness and soil variables. The classification of the vegetation samples resulted in the identification and subsequent description of 26 riverine and 11 mire communities. The riverinecommunities have been subdivided into ten Community Groups, including a group of Aquatic communities and three groups of Wet Bank communities. The main distinction within the Wet Bank Zone is the importance of erosion or deposition as a driving force of the ecosystem. Three groups of Fynbos communities are identified in the Back Dynamic Zone, with Asteraceous Fynbos occurring on shales and granites, Ericaceous Fynbos occurring on Table Mountain Group sandstones and Transitional Fynbos on a variety of substrates. One community group is characterized by the dominance of Cliffortia odorata, which shows affinity with some renosterveld communities known from literature. The two final groups contain the Afromontane Forests and Riparian Scrub communities, respectively. Discharges are calculated from data recorded at existing gauging weirs. The recurrence intervals, inundation levels and stream power of several flood events are derived from these data and are extrapolated to upstream sites. It appears that most vegetation types in the zonation pattern on the riverbank can be explained by these flood events, except for the Afromontane Forests, which are dependent on other sitespecific factors including protection from fire. Constrained and unconstrained ordinations are used to relate vegetation patterns to the environment. The vegetation is determined by three environmental gradients, operating at different scales. The lateral gradient across the riverbed is mainly determined by inundation frequency and stream power, which are difficult to measure in rocky mountain situations, although variables like distance from the water’s edge, elevation above the water level and rockiness are correlated to them. The longitudinal gradient is the gradient along the length of the river, from high to low altitude. This gradient has the least influence on the riparian vegetation. The geographical gradient reflects the large-scale climatic processes across the mountain range. This gradient accounts for the biggest part of the total explained variation. Important variables are especially the ratio between the summer and winter rainfall and the geological substrate. In the Fynbos Biome, where gamma diversity is extremely high, large-scale environmental processes are important in azonal vegetation as well. The most species-rich vegetation associated with the rivers is found furthest from the water’s edge at intermediate altitudes. Knowledge about the vegetation types and environmental processes in Western Cape rivers is essential for monitoring and maintaining these special ecosystems. Specific threats are related to possible abstraction of water from theTable Mountain Group aquifer and from climate change, which might result in an overall drying of the ecosystem.
AFRIKAANSE OPSOMMING: Riviere se oewerplantegroei kry die laaste tyd baie aandag in Suid-Afrika, hoofsaaklik vanweë die belang vir die beheer van vloede, stabilisasie van die oewers en die bewaring van drinkwater. Die hoë-liggende dele van die riviere het tot dusver die minste aandag geniet omdat hulle tot ’n groot mate ontoeganklik is weens die onherbergsame terrein waarin hulle geleë is. In hierdie studie is daar veral na bergstrome gekyk waar die plantegroei nog taamlik natuurlik en onversteur is. Die studiegebied wat vir hierdie doel gekies is, is die Hottentots-Holland berge in die Wes-Kaap. Die gebied het die hoogste reënval in die Kaapse Floristiese Ryk en is ook baie ryk aan spesies. Vyf riviere het in hierdie gebied hulle oorsprong. Die plantegroei wat hier voorkom sluit ‘n wye reeks habitatte in: van hoog tot laag in hoogte bo seespieël, verskeie geologiese substrate asook verskillende reënval patrone. Al die vyf riviere wat ondersoek is, is baie versteur in hul onderlope, maar is nog grotendeels natuurlik in hul hoë-liggende dele. Almal is reeds opgedam deur een of meer damme, behalwe die Lourensrivier. ’n Tussenopvanggebied-oordragskema verbind tans die Eerste-, Berg- en Riviersonderendriviere met mekaar. Die water uit hierdie riviere word tans hoofsaaklik in die Theewaterskloofdam opgegaar. ’n Verdere groot opgaardam, die sogenaamde Skuifraamdam, word binnekort in die Bergrivier te Franschhoek gebou. Al die riviere se onderlope is tot ’n mindere of meerdere mate vervuil met landbou- en rioolafvoerprodukte. Uitheemse indringerplante, wat die natuurlike oewerplantegroei verdring, skep veral probleme stroomaf van plantasies en dorpe. Om die plantegroei van die rivieroewers na te vors, te klassifiseer en te beskryf, is variasies in die fisiese omgewing bepaal en korrelasies gesoek om die verspreiding van die plantegroei te verklaar. Die belangrikste verdeling in die oewerplantegroei wat gevind is, is tussen die Nat-oewersone (dit word meer as een keer per jaar oorstroom) en die Droë-oewersone (dit word minder as een keer per jaar oorstroom). Die Droë-oewersone word verder onderverdeel in die Laerdinamiesesone, die Boom/Struiksone en die Agter-dinamiesesone. In die laer dele van die rivier is hierdie soneringspatrone baie duidelik, maar in die boonste dele van die rivier kan die onderverdelings dikwels nie van mekaar onderskei word nie omdat hulle gemeng is, of kan die sones baie smal wees of selfs heeltemal afwesig wees.Die plantegroei is gemonster in transekte wat dwarsoor die rivierloop uitgelê is. Die Braun-Blanquet monstertegniek is gevolg. Bykomende monsterpersele is opgemeet in die moerasse in die boonste dele van die berg-opvanggebiede. Om die omgewingsprosesse wat die plantegroei bepaal te verstaan, is ’n aantal omgewingsfaktore in elke monsterperseel aangeteken, wat, onder andere, helling, aspek en bedekking van rotse ingesluit het, terwyl die variasie in samestelling van die bodem ook aangeteken is. Die klassifikasie van die plantegroei het tot die beskrywing van 26 plantgemeenskappe in die riviere en 11 gemeenskappe in die moerasse gelei. Die struktuur van die plantegroei asook kenmerke van die fisiese habitat is in die beskrywing van die plantegroei-eenhede ingesluit. Die gemeenskappe in die riviere is onderverdeel in tien gemeenskapsgroepe. Daar is een gemeenskapsgroep wat die akwatiese gemeenskappe en drie wat die Nat-oewersone gemeenskappe insluit. Die belangrikste verskille tussen die verskillende Nat-oewersone gemeenskappe word bepaal deur die mate waartoe erosie of deposisie voorkom. Daar is ook drie gemeenskapsgroepe van Fynbos onderskei wat in die Agter-dinamiesesone voorkom. Dit sluit in die Aster-fynbos op die skalies en graniete, die Erica-fynbos op die sandstene en die Oorgangs-fynbos op gemengde substrate. Een gemeenskapsgroep is deur die dominansie van Cliffortia odorata gekenmerk. Dit toon verwantskap met renosterveld gemeenskappe wat reeds in die literatuur beskryf is. Die laaste twee groepe sluit die Afromontane woude en Oewerstruikbosse in. Die waterafloop is bereken deur middel van data verkry vanaf bestaande keerwal meetstasies. Die herhalings-intervalle, oorstromingsdiepte en vloei-sterkte van verskillende vloedtipes word vanaf hierdie data afgelei en stroomop geekstrapoleer. Die meeste plantegroeivariasie op die oewers kan deur die vloede verklaar word, behalwe in die geval van die Afromontane woude, wat deur ander omgewingsfaktore bepaal is. Beperkte en onbeperkte ordinasie is gebruik om die verband tussen die plantegroeipatrone en die omgewing te bepaal. Die plantegroei se verspreiding is bepaal deur drie omgewingsgradiënte, wat op verskillende skale ‘n uitwerking het. Die laterale gradiënt oor die rivierbedding is hoofsaaklik bepaal deur oorstromingsfrekwensie en stroomvloeisterkte. Hierdie veranderlikes is moeilik bepaalbaar, alhoewel ander soos, afstand vanaf die rivier, hoogte bo watervlak en bedekking van rotse, wat hieraan gekorreleer is, wel meetbaar is. Die lengte gradiënt,dit is die gradiënt wat van oorsprong na einde langs die lengte van die rivier teenwoordig is, het die minste invloed op die plantegroei. Die geografiese gradiënt weerspieel die grootskaalse klimaatsveranderinge oor die bergreeks. Deur hierdie gradiënt word die grootste deel van die totale variasie tussen die monsters verklaar. Die belangrikste veranderlikes is die verhouding van somer- teenoor winter-reënval en die geologiese substraat. Soortgelyk aan die fynbos in die Fynbosbioom, waar gammadiversiteit buitegewoon hoog is, is die grootskaalse omgewingsprosesse, ook vir asonale oewerplantegroei, baie belangrik. Die spesierykste plantegroei rondom die rivier word die verste van die oewer op gemiddelde hoogtes bo seespieël gevind. Kennis oor die plantegroei en die omgewingsprosesse in die riviere in die Wes-Kaap is belangrik vir die monitering en effektiewe beheer van hierdie besondere ekosisteem. Spesifieke bedreigings is gekoppel aan die potensiële ontginning van water uit die akwifer in die Tafelberggroep-sedimente asook deur grootskaalse klimaatsveranderinge waartydens die hoeveelheid water, volgens voorspellings, waarskynlik sal afneem in hierdie ekosisteem.

The entire thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file; a non-technical public abstract appears in the public.pdf file. Title from PDF of title page (University of Missouri--Columbia, viewed on October 16, 2009). Thesis advisor: Dr. Richard P. Guyette. Includes bibliographical references.

Wetlands provide a number of valuable functions to both the surrounding environment and society. The anaerobic conditions created by flooding in wetlands provide a habitat that supports unique assemblages of plant life. High altitude wetlands are amongst the most species-rich in South Africa. They house a number of rare species and play a vital role in the supply of water to lower lying areas. These are some of the reasons that mountain wetlands are of high conservation value. A phytosociological study was undertaken on the high altitude wetlands of the Great Escarpment with the aim of classifying the plant communities and identifying the environmental drivers of plant community patterns within these ecosystems. Data collection was focused in the Eastern Cape and was supplemented with data from existing studies to gain a more complete understanding of the wetlands of the Great Escarpment of South Africa. Using the Braun-Blanquet approach, Hierarchical Cluster Analysis and Indicator Species Analysis; five broad wetland groups were identified, comprised of 33 individual plant communities and 81 indicator species. Multivariate analysis, including Canonical Correspondence Analysis revealed that the effects of altitude, such as temperature and rainfall, are the most significant large-scale drivers of vegetation patterns. Smaller scale drivers include wetness and soil nutrients including nitrogen, phosphorus, electrical conductivity, sodium, and organic content. The identification of indicator species served to reveal potentially important wetland species across different areas of the Great Escarpment. The effects of altitude on plant community patterns highlights the susceptibility of the high altitude specific communities to upward temperature zone shifts resulting from global warming. Other threats include livestock trampling, water extraction, and land use change for agricultural purposes. The relative absence of alien species in these wetlands gives an indication of their pristine condition and therefore their importance as a reference from which they may be monitored. A large proportion of the wetlands studied here occur outside protected areas, and given the rate of wetland loss in South Africa, it is important that continued effective land management is practiced to ensure that these ecosystems are conserved in the future .

Snowbed vegetation contains both vascular plants and bryophytes. The latest snowbeds cover areas that are of predominantly, if not exclusively, bryophyte flora while the vascular plants are generally confined to the periphery of such late snowbeds. It is hypothesised that the exclusion of vascular flora from the snowbed core is the result of the shortened growing season generated by late-lying snow, which the bryophyte flora is better able to tolerate. The snowbed bryophytes cannot, however, tolerate the competition offered by the vascular flora in the peripheral areas from which they are absent. Data indicate that some of the bryophyte snowbed species are inhabiting optimal conditions in the snowbed core, rather than tolerating sub-optimal conditions. Adaptation and acclimation responses observed in peripheral vascular species indicate that these are inhabiting sub-optimal conditions in the snowbed periphery. The relationship between snow-lie and climate is examined, with to the construction and examination of a second hypothesis that snowbed loyalty in the Scottish Highlands is high, while duration of snow cover is variable. Snow-lie loyalty is the product of prevailing wind conditions, which are persistent and consistent in Scotland leading to consistency in late snowbed location, while the occurrence of mid-winter thaws at all altitudes makes duration of snow cover through accumulated snow depth much more variable. Increased zonal flow in winter has affected snow-lie in the Scottish Highlands, with a slight decrease in snow-lie duration in recent years. It is not clear whether this pattern applies to all altitudes and accumulations at higher levels, especially in the western Highlands, may be increasing as a result of steeper winter-time lapse rates. With late snowbed location varying very little, it is possible that the consequences of global warming may not necessarily mean an extinction of the late snowbed bryophytes in Scotland, which constitute an important part of Britain's montane flora.

Hybrids are common, being found in about 25% of all plant species, but the isolating barriers which preserve species integrity are poorly studied. I investigated this question in the large New Zealand genus Celmisia Cass. (Asteraceae), which hybridises readily in cultivation, but wild hybrids are relatively rare. My study quantitatively tests four potential reproductive isolating barriers in 12 sympatric species of Celmisia found in the Craigieburn Range, inland Canterbury, New Zealand. I examined two potential prezygotic reproductive isolating barriers (flowering phenology and pollinator specialisation), and two potential postzygotic barriers (pre-dispersal seed predation and hybrid seed germination). I used null models to test whether Celmisia species had temporally segregated flowering times, and found that some Celmisia are temporally segregated and thus less likely to form hybrids. I used experimental pair-wise flowering arrays to observe insect visitation to six different Celmisia species pairs. While I found no difference in the overall pollinator community, several insect families showed preferences for some Celmisia species. Furthermore, I found that subtle floral character differences were driving these insect preferences. In particular, I found scape height to be positively associated with insect visitation with taller Celmisia being favoured over shorter species. Insect preferences did not translate into strong floral constancy, therefore indicating that Celmisia flower visitors are likely to be a weak barrier to hybridisation. I reared a range of insect seed predators from field-collected capitula of the hybrid C. x pseudolyallii and both parent species (C. lyallii and C. spectabilis). There was no overall difference in the number of seed-predators per capitulum between hybrid and parent Celmisia taxa. I collected and sowed seeds from three Celmisia hybrids and their parent species in order to test whether hybrids were less fertile than their parent species. I found no evidence to suggest that the seeds of hybrids had lower germination success than those of their parents. Overall I found evidence for only weak prezygotic reproductive isolation and no evidence for postzygotic isolation in the four barriers I examined in Celmisia.

Thesis (M.A.)--Central Connecticut State University, 2000.
Thesis advisor: Kim A. Wilson. " ... in partial fulfillment of the requirements for the degree of Master of Arts in Biology." Includes bibliographical references (leaves 56-62).

A lodge at Crowder's Mountain provides the opportunity through which to investigate the contextual relationship between a natural undisturbed site and the introduction of a man-made environment. responsible design should instill a ‘sense of place’ by addressing the special forces within each site. in search of this ‘sense of place’ my efforts involve the development and integration of forms, materials, and spaces which are generated directly from the physical and qualitative characteristics of the site.
Master of Architecture

The similarities in the structure of the sclerophyllus evergreen shrublands of the five disjunct mediterranean-type ecosystems is thought to be the result of convergent evolution. In the Mediterranean, California, and Chile the length of the summer drought and the cold winter temperatures are hypothesized to be the primary selective pressures. In Australia and South Africa low soil nutrients are thought to be important, as they are in defining the structurally similar heathlands found with a range of climatic types. The fynbos vegetation in an area with a mediterranean-type climate was sampled for a period with low xylem pressure potentials and restricted leif conductances to water loss during the summer drought, and the patterns of plant response to desiccation. The presence of patterns of plant water relations in the fynbos similar to those found in other mediterranean-type ecosystems could demonstrate the importance of water as a selective pressure in the fynbos.

The aim of this thesis was to explore the distribution of the taxonomic, phylogenetic and functional components of plant diversity in high mountains, and to show how different components of diversity have responded to land-use and climate change over the last two decades. To address this aim, we used a multiple approach at different scales, by combining information from biodiversity databases and descriptive and experimental data gathered in the field. Some methodological improvements were implemented to account for the main sources of uncertainty inherent in the baseline data. The study was conducted in the Central Pyrenees, mainly in the Ordesa-Monte Perdido National Park (OMPNP). In Chapter 1 we developed a novel method to assess the effect of the sampling effort when using information of classical databases to analyze spatial diversity patterns. Such method was used in chapter 2 to identify hotspots, and results were compared with the ones produced by an unbiased database information (standardized community surveys), Finding an overall spatial mismatch among the different diversity components at small scale (Chapter 2). Grasslands resulted to be the richest habitat in terms of species and endemisms, whereas the highest values of phylogenetic and functional diversity were observed in some forests, specially among the mixed ones. The second part of the thesis analyzed recent trends of the richest plant communities in high mountain ranges, alpine grasslands, to the generalized reduction in grazing and climate warming. In chapter 3 we compared plant community composition and tree cover in the upper limit of the treeline ecotone between 1998 and 2009. A weak effect of the increase in tree cover on the dynamics of Field layer vegetation was found, evidencing the slow response of alpine plant communities to drastic structural changes in the habitat. In chapter 4, we revisited after two decades 12 sites along an elevational gradient in two valleys of the Central Pyrenees. After accounting for the effect of the resampling error and the natural fluctuations of communities, we found that alpine grasslands were relatively stable over time at community, species and trait level. Evidences of the large ecological inertia of alpine grasslands were also Found in two experimental exclusion of herbivores set 20 years ago where species richness did not significantly differ from control grasslands (Chapter 5). Differences in the community trajectories of ungrazed and control grasslands occurred only during a sequence of warm and dry growing seasons, which led us to conclude that the effects of the grazing reduction and climate warming acted synergistically. Taken together, these results indicate that the response of alpine grasslands to land-use and climate change may be weaker and slower than expected according to predictive models and observations made in several grasslands below the treeline (rapid ecological succession after abandonment) and mountain summits (thermophilization) in the Central Pyrenees. The apparent stability of alpine grasslands depicted in our studies may revert as some tipping points are exceed. However, the smooth response of grasslands may provide a good opportunity to implement timely management actions for the conservation of this exceptionally rich habitat. The maintenance, and in some cases restoration, of traditional grazing activities, might be the simpler and more efficient strategy in the Face of global change, and perhaps the only possible to alleviate the impact of climate warming on plant diversity.
En esta tesis investigamos la distribución de los componentes taxónomico, filogenético y funcional de la diversidad vegetal en la alta montaña, y cómo ha respondido a los principales motores de cambio global en montañas (cambio climático y de uso de suelo) en las últimas décadas. Para abordar estas dos cuestiones usamos una aproximación a varias escalas, combinando información recopilada en bases de datos con datos descriptivos y experimentales obtenidos en campo, poniendo especial énfasis en mejorar los métodos analíticos de las aproximaciones utilizadas. Nuestra investigación se llevó a cabo en el Pirineo Central, especialmente en el Parque Nacional de Ordesa y Monte Perdido (PNOMP). En el primer capítulo examinamos el sesgo del esfuerzo de muestreo en una clásica base de datos de herbario, y cómo éste puede afectar a los análisis de los patrones de diversidad. Desarrollamos un método nuevo que permitió detectar diferencias importantes en la distribución del esfuerzo de muestreo a lo largo del PNOMP. Esta información fue usada en el segundo capítulo, donde demostramos por primera vez que, además de la riqueza específica, el patrón de distribución del resto de los componentes de la diversidad puede verse distorsionado por el sesgo de muestreo. Tras utilizar una base de datos elaborada a partir de inventarios de comunidades, observamos que los diferentes componentes de la diversidad presentaron una distribución distinta a lo largo del PNOMP. Este resultado demuestra que nuestra habilidad para identificar áreas prioritarias para la conservación a partir de bases de datos clásicas de diversidad es muy limitada. Los pastos resultaron ser el hábitat más rico en término de número de especies y endemismos, mientras que algunos tipos de bosques de hoja caduca fueron identificados como puntos calientes de historia evolutiva y funcional. En los siguientes capítulos examinamos la respuesta de las comunidades más ricas, los pastos de alta montaña, al descenso generalizado del pastoreo y el calentamiento climático. En el capítulo tercero analizamos los resultados de la revisita de transectos de vegetación situados en el ecotono del límite del bosque superior, muestreados 11 años antes. El escaso efecto del incremento de la cobertura arbórea sobre las comunidades pone de manifiesto la lenta respuesta de las comunidades alpinas a cambios estructurales del hábitat. En el cuarto capítulo examinamos la respuesta de los pastos alpinos a lo largo de dos décadas, tras revisitar una docena de parcelas permanentes distribuidas a lo largo de un gradiente altitudinal en dos valles del Pirineo Central. Tras considerar el error de muestreo y la fluctuación interanual de las comunidades, no observamos señales evidentes de cambios ni a nivel de comunidad ni de especies, ni tampoco un aumento de especies leñosas. Los grupos de especies con tendencias opuestas no mostraron rasgos funcionales significativamente diferentes, cuando fue considerada la abundancia y autocorrelación evolutiva de éstos. La gran inercia ecológica de los pastos alpinos fue también confirmada en un experimento de exclusión de herbivoría que duró 19 años (quinto capítulo), donde la riqueza de especies no mostró un efecto significativo en respuesta al tratamiento. La ausencia de ganado sólo resultó en una trayectoria divergente de la comunidad tras una década, y coincidiendo con un periodo excepcionalmente cálido y seco. Este resultado sugiere que el cese del pastoreo y el aumento de las temperaturas podrían tener un efecto aditivo sobre las comunidades vegetales. En conjunto, todos estos resultados ponen de manifiesto que las comunidades de pastos alpinos frente a los principales motores de cambio en montaña puede ser más lenta de lo que se esperaba según los modelos predictivos, la rápida sucesión ecológica (matorralización) observada en varios pastos subalpinos y montanos a lo largo del Pirineo, y los cambios en las comunidades de cumbres (termofliación) descritos en el propio PNOMP. La aparente estabilidad registrada en nuestro estudio podría revertir si se sobrepasan puntos de inflexión críticos. Sin embargo, la lenta dinámica aquí observada sugiere que no es tarde para tomar medidas de gestión para garantizar la conservación de estos pastos excepcionalmente ricos. El mantenimiento o restauración de las actividades del pastoreo tradicional se vislumbra como una solución simple y efectiva para paliar los efectos de los principales motores de cambio global sobre las comunidades alpinas.

Big sagebrush (Artemisia tridentata Nutt.) is the most widespread and common shrub in the sagebrush biome of western North America. Of the three most common subspecies of big sagebrush (Artemisia tridentata), mountain big sagebrush (ssp. vaseyana; MBS) is the most resilient to disturbance, but still requires favorable climactic conditions and a viable post-fire seedbank for successful unassisted recovery. This study was designed to assess MBS seed production throughout post-fire recovery. We performed 2 pilot studies to develop methods for estimating seed production and plant age. The results of the pilot studies and a space-for-time substitution strategy were used to measure seed production on 13 sites ranging from 10-33 years post-fire. We hypothesized that seed rain (mean seeds produced/ m2) would peak before stand density had maximized due to decreasing individual plant fecundity (mean seeds produced/ plant) in high density stands. We measured population density and individual plant fecundity for three size classes of MBS and used forward stepwise regression analysis to identify environmental factors influencing seed production over time. Density for small (basal stem diameter (BSD) <1 cm) and medium-sized (BSD=1-3 cm) plants was consistently low and was not affected by time since fire (TSF), while large-sized (BSD > 3 cm) plant density increased steadily with TSF (p=0.0002). Plant fecundity decreased with TSF for all three size classes (p range = 0.019 – 0.0506), with large plants dominating reproductive output. Small and medium-sized plant fecundity was negatively correlated with winter precipitation (p range = 0.0106-0.0174), while large plant fecundity was positively correlated with winter precipitation (p<0.0001) and negatively correlated with elevation (p=0.0001). Despite losses in plant fecundity over time for all size classes, steady recruitment in population density resulted in increased seed rain (p=0.0039), suggesting that increases in stand density compensated for losses in individual plant fecundity. Results partially support our hypothesis that the time required for MBS seed rain to be maximized was not tightly bound to indicators of stand maturation. Understanding the factors that influence post-fire seed production can help land managers better manage for successful recovery by providing them with tools for evaluating seed production capabilities of MBS communities.

Vor dem Hintergrund der aktuellen Herausforderungen im Management natürlicher Ressourcen und dem Bedarf geeigneter Institutionen, um diesen Herausforderungen gerecht zu werden, untersucht die vorliegende Arbeit ein Managementsystem für Wasserressourcen im Bundesstaat Wyoming, USA. Die Autorin untersucht die über 100-jährige Geschichte der Wasserrechte im landwirtschaftlichen Bewässerungssektor. Die Studie zeigt, wie und warum die Verfügungsrechte zwischen privaten Nutzern und der staatlichen Administration hin und her geschoben wurden und welche Konsequenzen dies brachte. Sie kommt zu dem Schluss, dass das System im Laufe des letzten Jahrhunderts gegenüber seinem Hauptzweck – der Bewässerung – als resilient gelten kann. Was jedoch andere neuere Funktionen angeht, im Besonderen die Nutzung ohne Verbrauch ist das System als weniger resilient einzustufen. Die Arbeit trägt zu einer Weiterentwicklung der Theorien des institutionellen Wandels bei. Die Autorin zeigt die Wichtigkeit von extremen physischen Bedingungen, wie geringer Niederschlagsmenge, kurzen Wachstumsperioden oder schwierigen Bodenverhältnissen, für den institutionellen Wandel. Solche Gegebenheiten können zu pfadabhängigen Veränderungen führen. Gleichzeitig diktieren sie den Rahmen, innerhalb dessen ein stärkerer institutioneller Wandel im natürlichen Ressourcenmanagement möglich wäre.
Given the need for institutions managing natural resources that can be foundations for dealing with challenges like climate change, this dissertation examines more than 100 years of a water resource management system in the Western U.S., in the state of Wyoming. The dissertation identifies the key actors in this system as water users and the water administrators in the state government. The study determines that the Wyoming system distributes property rights in water between users and the state. The study finds that over a century the system has proved itself resilient towards its most longstanding users, in irrigated agriculture. However, the system has lacked a resilient response to new demands, particularly non-consumptive uses of water. In a contribution to theories of institutional change, the dissertation demonstrates the important role in natural resource management systems played by harsh physical conditions such as lack of precipitation, short growing seasons, and difficult terrain. These conditions can create path dependency and dictate the circumstances that allow path-breaking in natural resource management institutions.

This report presents Native American interpretations of and concerns for plant resources on or near Yucca Mountain, Nevada. This is one of three research reports regarding Native American cultural resources that may be affected by site characterization activities related to the Yucca Mountain high -level radioactive waste disposal facility. Representatives of the sixteen involved American Indian tribes identified and interpreted plant resources as part of a consultation relationship between themselves and the U.S. Department of Energy (DOE). This report integrates data from the ethnobotanical fieldwork and visits conducted over a three -week period. The bulk of this report divides plants into their logical components: plant parts used; places where used; purposes of uses; and persons who used, do use, and will use the plants. The remainder of this Introduction is devoted to conveying an American Indian holistic perspective on plants as a part of the world.

The interaction between Xylocopa californica and Chilopsis linearis was used to test the hypothesis that nectar robbing is costly to plants. No evidence for these costs, either in terms of decreased pollination or increased energy demands, was found. In fact, the mean number of seeds per fruit and the mean individual weight of seeds per fruit was higher from fruits that developed from robbed flowers than from fruits that developed from unrobbed flowers, indicating that the presence of Xylocopa californica enhanced pollination. Chilopsis linearis pollen was isolated from the tips of the abdomens of robbing Xylocopa californica and it was determined that these bees could be transferring pollen from flower to flower as they position themselves to rob. This association was found to be one of mutual benefit rather than one of exploitation.

Given a sloping wooded site in the Blue Ridge Mountains of North Carolina, the problem of the thesis project was to design a retreat that would fit the environment and the people that would inhabit it. It was a searching for the interdependence between the landscape and the building. Equally important was a search for a structure that would give architectural integrity to the house. The design process included a time of discovery and clarification of values and priorities. Two additional steps during the schematic design were processes architect Charles Moore referred to as"mapping" and"collecting''. These processes help to establish relationships between the inhabitants and things they recognize. Structural elements of post and beam construction gave a sense of order in the design layout and helped to organize the spaces within the form of the house. A system of equidistant columns formed by four wood posts also provided the physical linkage between the building and the site. Native field stone was used for the large piers that supported the columns as well as for the perimeter walls of the living room structure. The inner landscape of the house, the pathways, the rooms and the machines within them, developed from the basic idea that the building would grow from a central axis or “spine” that originated from the outside at the street's edge, extended across the site,and moved into the building to become the main artery of the structure as well as the connection between outside and inside.
Master of Architecture

The site is the Northwest side of Paris Mountain overlooking the valley, flat fields and the winding road along the river. The monastery is thought of as a whole encompassing its various parts: the church, the monk's dormitory, the library, the winery, the bakery, the barns and the field chapel. Also in the enclosure are the elementary school with its classroom building, the administration/theatre building and the gymnasium. There is an imposition of a two-dimensional grid on the natural contour of the mountainside, thus resulting in a grid-like fabric which becomes the origin of a mathematical ordering throughout the site enclosure. The "Grid" is one of directional "force lines" which reflect and generate a relationship between the various buildings as well as their interrelationship to the site. This ordering is not one of predictable "constants" yet more one whose purpose is to be manipulated, eroded, extended and disassembled according to "aesthetic demands" which occur throughout the project. It is not one of a finite programming; however, there is a sense of rational consequences which result as part of this ordering. The "base grid" may eventually be eroded to such a level that what remains is more of a memory of this ordering than of anything clear and distinct in one's perception of it. The extension of this grid is meant to go beyond the confines of the monastic enclosure - as to give a sense of relationship between surrounding fields, roads to the monastery, landscaping and transitional spaces to that which lies within the walls. The solidity of these enclosing walls is one of historical reference to times past. An erosion of the walls also occurs so as to leave them more as skeleton-like markings or ruins, of a fortress which never was. The result being an architectural imposition with directional qualities interrelating site and structure.
Master of Architecture

The subject for this thesis is the design of a theater and amphitheater for chamber music, upon a beautiful site-- a mountain meadow. The site, context and program which serve as a starting point for the new design are based on a real site and context: that of an existing center for chamber music, situated high in the mountains, housed in the buildings of an old estate. In creating the design for the new building, it was attempted to achieve and integrate several goals: • To create spaces (a theater and an amphitheater) which would enhance the experience of (listening to) chamber music-- both visually and acoustically. • To address the functional and practical requirements for a building which is to be used as a center for the performance of music. This includes the resolution of a whole range of architectural concerns, including such issues as: structure; form; program and plan; the use of materials; public and private areas; entrance and circulation; the use of daylighting; the framing of views; an attention to human scale; and the design of a building with the consistency to 'read’ as a whole, rather as than an assemblage of parts. • To take advantage of the beautiful landscape and view from the new building site, and to attempt to integrate the form and character of the new building sensitively and gracefully onto the existing site.
Master of Architecture

In the past sixty years, the Southern Alps have undergone a tremendous and likely unprecedented change in land-use due to land abandonment in mountain regions. This phenomenon causes a turn of mountain grasslands to forests through the process of natural succession. Vegetation relevés in eight pastures under forest succession in the Italian Alps were collected at different percentage of wood cover. Moreover, in four of the eight sites, herbage samples were collected at different wood cover levels. In addition, in one site (characterised by Nardus grassland habitat) core samples were collected in order to study root characteristics. Species richness, botanical composition, dry matter production and contents, and root characteristics were taken into account in order to analyze the effect of wood cover on plant diversity, herbage yield and quality, and soil stability. The effect on specie richness due to this process is different among sites because of differences in environmental factors and human activities. In general species richness decreased with increasing wood cover, and the reduction was more relevant in sites at low altitude. In some sites the effect of reforestation on plant species richness showed a slight increase at low percentage of wood cover followed by a gradual decrease, while in the others the effect displayed a monotonic decrease. Modelling with a generalized linear mixed model suggested that mean annual temperature was the primary determinant of the functional relationship. Differences among sites were not found when botanical composition, and in particular Bray dissimilarity index, was taken into account. A reduction of dry matter yield was noted in most of the studied sites. Forest succession affected herbage quality decreasing it starting from low percentage of wood cover because of changes in crude protein and fibrous contents. When root characteristics were analyzed, root length density and average diameter declined at 75% of wood cover increasing the risk of soil erosion. Based on this results, mountain areas with low relevance for dairy production grazing should be encouraged for preserving both biodiversity and the stability of habitat. The strong effect of temperature on the loss of species richness suggests that the risk increases with lower altitude and stronger exposition towards South. The maintenance of low percentage of wood cover is useful for the habitat ecological value. On the contrary, in mountain areas where dairy production grazing is relevant, the management should be assessed for excluding wood establishment on the grazing surface.
Negli ultimi sessant’anni, nell’ambiente alpino ed in particolare nelle Alpi italiane, si è assistito ad un importante e senza precedenti cambiamento d’uso del suolo, dovuto all’abbandono delle zone montane. Questo fenomeno ha causato un avanzamento del bosco su prati e pascoli attraverso un processo naturale di riforestazione. Per questo studio sono stati eseguiti rilievi floristici in otto pascoli montani delle Alpi italiane, soggetti ad avanzamento del bosco. Inoltre, in quattro di questi otto siti sono stati raccolti campioni di foraggio per la determinazione della produttività e della qualità della fitomassa. Infine, in un sito, caratterizzato dalla presenza di habitat a Nardus stricta, sono state raccolte carote di terreno per la caratterizzazione della componente ipogea. In tutti i casi i rilievi e i campionamenti sono stati eseguiti a percentuali crescenti di copertura arboreo-arbustiva. Sono stati considerati i seguenti parametri: numero di specie, composizione botanica, produzione e composizione chimica della sostanza secca nonché densità e diametro medio della radici a diversi livelli di profondità nel terreno, in modo da analizzare l’effetto della copertura arboreo-arbustiva su diversità vegetazionale, produzione e qualità del pascolo e stabilità del suolo. L’effetto sul numero di specie causato dall’avanzamento del bosco è risultato diverso tra i siti a causa delle differenze che intercorrono nei fattori ambientali e nelle attività antropiche. In generale si è assistito ad una diminuzione del numero di specie per effetto dell’avanzamento del bosco, in alcuni siti però è stato osservato un leggero aumento per bassi valori di copertura arboreo-arbustiva. La diminuzione del numero di specie è stata più marcata nei siti ad altitudine inferiore. Usando un modello lineare misto generalizzato, è stato riscontrato che le temperature medie annue sono uno dei fattori che meglio spiegano la diversa relazione tra i siti. L’analisi della composizione floristica mediante l’indice di Bray, ha evidenziato un comportamento simile tra i siti. Nella maggior parte dei siti analizzati si è riscontrata una diminuzione della produzione in sostanza secca per effetto della copertura arborea. Inoltre, già a partire da basse percentuali di copertura arboreo-arbustiva, è stata osservata una diminuzione della qualità della fitomassa prodotta dal pascolo, per effetto di una diminuzione del contenuto di proteina grezza ed un aumento delle fibre. Relativamente alle radici, si è osservato come la densità radicale in lunghezza e il diametro medio diminuissero drasticamente a percentuali di copertura arboreo-arbustiva del 75%, aumentando verosimilmente il rischio di erosione del suolo. Sulla base di questi risultati possiamo dire che nelle regioni montane, laddove la vocazione produttiva (in termini di produzione casearia) è poco rilevante, andrebbe incoraggiato il mantenimento di questi habitat a vantaggio della biodiversità e della stabilità del suolo. Come visto in questo studio, l’effetto della temperatura media annua sulla diminuzione del numero di specie, suggerisce che il rischio di perdita di biodiversità aumenta ad altitudine minore e in aree esposte a sud. Il mantenimento di basse percentuali di alberi o arbusti può essere utile per conservare il valore naturalistico di questo habitat. Al contrario, nelle zone dove la vocazione casearia del pascolo è prevalente, la gestione dovrebbe essere tale da mantenere le superfici a pascolo completamente libere da alberi e arbusti.

The flora of southern Appalachian high elevation balds has strong representation of northern disjuncts and regional endemics. Among the endemics, the showy Lilium grayi (Gray’s Lily), is most noteworthy for its historical significance and for a high public profile. As bald vegetation changes in response to human and natural environmental shifts, active bald management has been implemented on public lands. Among managed balds, the Roan Mountain massif supports a large population of L. grayi. The purpose of this study was to describe the demography of adult plants, compare browsed and non-browsed plots, and determine the extent to which disease may impact survival and reproduction of L. grayi on Roan Mountain. There were no significant differences between browsed and control plots in measures of plant morphology, vigor, or reproductive output, but browsed plots had significantly more juvenile plants compared to controls. Along a transect, spatial analyses uncovered clusters of diseased and healthy plants and showed that plants in close proximity tended to be alike in disease status and those distant were more unalike. A pathogenic fungus, Pseudocercosporella inconspicua, may be the disease pathogen.

Includes bibliographical references (leaves 139-146).
Fynbos, the native vegetation of the Western Cape of Southern Africa experiences a mild, Mediterranean type climate with hot dry summers and cool wet winters. In terms of climate, fynbos is comparable with other Mediterranean systems found around the Mediterranean in Europe, in parts of Chile, south-western Australia and in the Chaparral in California (Aschmann, 1973). The Cape Floristic Region, of which fynbos is part, is one of the world's most botanically diverse regions, home to an estimated 9030 vascular species (Goldblatt, 1978; Goldblatt and Manning, 2002). The region has exceptionally high levels of endemism. Almost 69% of its 8920 species of flowering plants are endemic (Goldblatt and Manning, 2002), and, despite its small area, it is regarded as one of the six global plant kingdoms (Takhtajan, 1986). Ericaceae, Iridaceae, Proteaceae and the Restionaceae are well represented and there are a number of families that are endemic or nearly so (Goldblatt and Manning, 2002). The largest is the Penaeaceae, followed by Grubbiaceae, Roridulaceae and Geissolomataceae, which together contain 15 endemic genera (Goldblatt and Manning, 2002). These families are almost without exception evergreen sclerophyllous shrubs and are thought to be palaeoendemic remnants from an ancient temperate flora, when conditions were cooler and wetter (February et al., 2004). As a result, many of these species are restricted to wetter areas such as wetlands and mountain seeps (February et al., 2004). Many of these seeps, as well as other groundwater-fed ecosystems, are likely to be connected to the Table Mountain Group (TMG) aquifer from which the city of Cape Town may begin to abstract water.