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1
Lisi, Claudio S., Luiz C. R. Pessenda, Mario Tomazello e Kazimiers Rozanski. "¹⁴C Bomb Effect in Tree Rings of Tropical and Subtropical Species of Brazil". Tree-Ring Society, 2001. http://hdl.handle.net/10150/251653.
Abstract (sommario):
Atmospheric nuclear tests in the early 1960s introduced large amounts of radiocarbon into the atmosphere, which resulted in an increase of tropospheric ¹⁴CO₂ concentration by nearly 100% during the years 1964-1965. The bomb-produced ¹⁴C was then gradually incorporated within the global carbon cycle. The history of ¹⁴C concentration in the troposphere is preserved within annual growth layers of trees and can be reconstructed for those areas where direct measurements of 14C in the atmosphere were not performed. The paper presents results of ¹⁴C activity measurements in tree rings of tropical and subtropical species from Brazil, for the period 1945-1997. We investigated two species ( Araucaria angustifolia and Parkia sp.) growing at three sites covering the latitudinal band between 7 °S and 24 °S. The results indicate that the maximum ¹⁴C activity in the Southern Hemisphere occurred in 1965, with the Δ¹⁴C values reaching around 700%. Significant differences in Δ¹⁴C were recorded among the studied sites for the period of maximal ¹⁴C levels in the atmosphere, with the highest level observed at the tropical site and lowest in the subtropical zone. This reflects the dynamics of interhemispheric transport of ¹⁴C during the years of high spatial and temporal gradients of this isotope in the atmosphere.
2
Morrissey, T. "The effect of tree species on fluxes of nitrous oxide from forest soils". Thesis, University of York, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.428519.
3
Gindaba, Jiregna. "Water and nutrient relations of selected tree species of Ethiopia". Thesis, Stellenbosch : University of Stellenbosch, 2004. http://hdl.handle.net/10019.1/16050.
Abstract (sommario):
Dissertation (PhD (Bosb))--University of Stellenbosch, 2003.ENGLISH ABSTRACT: This study was conducted to evaluate and compare the water and nutrient relations of three indigenous deciduous tree species, viz., Cordia africana Lam., Croton macrostachyus Del., Millettia ferruginea (Hochst.) Baker and two widely planted eucalypts, viz., Eucalyptus camaldulensis Dehnh and Eucalyptus globulus Labill from Ethiopia. The study was organized as glasshouse and field observations in Ethiopia. Owing to the lack of baseline studies on the water and nutrient relations of the deciduous tree species, the glasshouse experiments involved a wide range of water and nutrient applications. Seedlings were grown with the supply of various levels of water and nutrients during which gas exchange, water potential, relative water content, tissue nutrient content and biomass production were measured. The field observations were limited to the study of surface root distribution and leaf nutrient composition of mature trees and their effects on soil nutrient pool. The observations were made on isolated trees and mixed or pure stands of trees in Badessa area, Eastern Ethiopia. The field site was selected because of the availability of the study species and suitability of the trees for the study. In the glasshouse, increased water deficit significantly reduced predawn leaf water potential, relative water content, stomatal conductance, photosynthetic rate, whole plant water use efficiency, plant height, diameter, leaf area and biomass production. Both of the eucalypts did not grow faster than the deciduous species under well-watered conditions unlike under water stress conditions. C. macrostachyus and C. africana had higher transpiration rates and tissue nutrient accumulations than the other species. They also demonstrated higher biomass allocation to roots than all the other species to support the intensive water and nutrient uptake rate. Due to the ability to re-orient its leaves to avoid direct solar irradiance, M. ferruginea maintained higher tissue water potential and relative water content than all the other species under water stress regimes. The impact of imposed drought was quick and more damaging to the eucalypts compared to the deciduous tree species indicating that the eucalypts may not survive extreme drought conditions unlike the deciduous species that drop their leaves and may remain dormant for weeks. The current study gave new experimental proof that E. globulus was more vulnerable to drought than E. camaldulensis. Soil N stress resulted in an overall reduction of tissue N concentration, N:P ratio, photosynthetic rate, stomatal conductance and photosynthetic water use efficiency in all the species studied. Pants with high foliar nitrogen concentration had higher photosynthetic capacities indicating that N plays a key role in photosynthesis and growth of all the studied species. The current study showed that for all the tree species, more attention has to be given to soil N than to P as soil P had minor effects on the photosynthetic activities of plants of all species compared to N.The investigation on tissue nutrient composition confirmed that N:P ratio could be used to detect Plimitation in plants. However, N:P ratio could not distinguish between N-limitation and combined limitations of N and P. The study of isolated C. africana and C. macrostachyus trees on soils in Badessa, Eastern Ethiopia indicated improved soil N, P and K under tree canopies whereas no effects were observed on the other soil nutrients studied. Similar to glasshouse conditions, C. macrostachyus and C. africana produced extensive surface roots, interfering with crops grown in association. Due to their high nutrient cycling potential the net effect on soil was positive. Comparison of E. camaldulensis woodlot and a mixed stand composed of deciduous species indicated that the fine root biomass in the surface soil under E. camaldulensis was about three times that under the mixed stand. The fine root biomass of E. camaldulensis inside the stand and 10 meters away from the stand were comparable in the surface soils showing the presence of root competition with adjacent crops. Therefore, planting of E. camaldulensis in association or adjacent to croplands should be avoided. Nutrient and carbon pool of soil inside the mixed stand was generally higher than that of E. camaldulensis indicating that trees of the mixed stand recycled more nutrients to the soil.
AFRIKAANSE OPSOMMING: Die doel van hierdie studie was om die verskille tussen water- en voedingstofverhoudings van drie inheemse blaarwisselemde boomsoorte te vergelyk, viz., Cordia africana Lam., Croton macrostachyus Del., Millettia ferruginea (Hochst.) Baker en twee bekende eucalyptus spesies, viz., Eucalyptus camaldulensis Dehnh en Eucalyptus globulus Labil van Etiopië. Die studie het bestaan uit kweekhuis- en veldobservasies in Etiopië. As gevolg van beperkte navorsing ten opsigte van water- en voedingstofverhoudings in bladwisselende boomsoorte, het die kweekhuis-eksperimente bestaan uit 'n wye verkeidenheid water- en voedingstoftoetse. Saailinge is gegroei deur verskillende vlakke van water- en voedingstowwe by te voeg. Gaswisseling, waterpotensiaal, relatiewe hoeveelheid water, hoeveelheid voedingstowwe en produksie van biomassa is gemeet. Die veldobservasies was beperk tot oppervlak-wortelverspreiding en blaarvoedingstof hoeveelhede van volwasse bome, sowel as die effek op grondvoedingstowwe. Observasies was beperk tot geïsoleerde, gemengde en een spesie opstande, in die Badessa area, Oos Etiopië. Die studiearea was gekies op grond van die voorkoms van die gekose boomsoorte, sowel as die toepaslikheid van die bome vir die studie. In die kweekhuis is gevind dat die verhoogte watertekort die pre-sonop blaarwaterpotensiaal, relatiewe hoeveelheid water, stomatiese geleiding, fotosintetiese tempo, heelplant water-gebruikseffektiwiteit, plant hoogte, diameter, blaararea en biomassa produksie beduidend verminder het. Nie een van die eucalyptus spesies het vinniger as die bladwisselende spesies onder voldoende hidrasie gegroei nie. Dit was egter nie die geval onder die waterbeperkte toestande nie. C. macrostachyus en C. africana het ‘n hoër transpirasie tempo sowel as weefselvoedingstof waardes gehad as die ander spesies. Hierdie boomsoorte se wortelbiomassa was ook meer as die ander spesies, om vir die tempo van water- en voedingstofopname te akkomodeer. As gevolg van die vermoë om blare te kan oriënteer om direkte sonlig te vookom, het M. ferruginea ‘n hoër water-weefselpotensiaal en relatiewe waterinname gehad in vergelyking met die ander boomsoorte in beperkte water toestande. Die impak van gëinisieerde droogte het vinnig voorgekom en het meer skade aan die eucalyptus aangerig in vergelyking met die bladwisselende boomsoorte. Dit dui aan dat die eucalyptus-spesie nie ekstreme droogte kan oorleef nie, waar bladwisselende spesies hul blare laat afval en vir weke aan een dormant kan bly. Hierdie studie gee eksperimentele bewyse dat E. globulus minder bestand is teen droogte as E. camaldulensis. Beperkte N in die grond het veroorsaak dat daar ‘n algemene vermindering van weefsel Nkonsentrasie, N:P ratio, fotosintetiese tempo, stomatiese geleiding en fotosintetiese watergebruiks effektiwiteit in al die bestudeerde spesies was. Plante wat oor hoër blaar-stikstofkonsentrasiesbeskik, het hoër fotosintetiese kapasiteite wat aandui dat N ‘n belangrike rol in fotosintese en die groei van al die bestudeerde spesies speel. Die oorhoofse bevindings van die studie was, dat daar meer aandag gegee moet word aan grond-N as P omdat grond-P net ‘n kleiner rol speel in die fotosintetiese aktiwiteite van plante van al die spesies in vergelyking met N. Die ondersoek na weefselvoedingstof hoeveelhede het bewys dat die N:P ratio gebruik kan word om P-tekorte in plante aan te dui. Die N:P ratio kan egter nie die verskil in N-tekorte en gekombineerde tekorte van N en P aandui nie. Die studie van die geïsoleerde C. africana en C. macrostachyus bome op grondtipes in Badessa, Oos Etiopië het verbeterde grond-N, P en K onder kroondak gebiede getoon, daar was egter geen verskille in die ander grondvoedingstowwe wat bestudeer is nie. In toestande gelykstaande aan die van die kweekhuis, het C. macrostachyus en C. africana meer oppervlaksswortels ontwikkel. Die toename aan oppervlakswortels het ingedring op gewasse wat in assosiasie gegroei is, dit het egter ‘n positiewe effek op die grond gehad as gevolg van die hoë voedingstof-siklus-potensiaal. Die E. camaldulensis opstand is gevergelyk met ‘n gemengde opstand van bladwisselende spesies waar daar gevind is dat die fynwortel biomassa in die oppervlak grond onder die E. camaldulensis ongeveer drie keer soveel was as die van onder die gemengde opstand. Kompetisie met aangrensende gewasse is aangeui deurdat die fynwortel biomassa van E. camaldulensis binne die opstand en 10 meter weg van die opstand vergelykbaar was in die oppervlakgronde. Dit dui dus aan dat die plant van E. camaldulensis in assosiasie of aangrensend aan gewasse vermy moet word. Die teenwoordigheid van voedingstowwe en koolstof in die grond van die gemengde opstand was oor die algemeen hoër as die van die E. camaldulensis. Dit is ‘n aanduiding dat die bome van die gemengde opstand meer voedingstowwe aan die grond verskaf.
4
Hill, J. L. "The effect of forest spatial geometry on tree species diversity in tropical forest patches". Thesis, Swansea University, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.637276.
Abstract (sommario):
Species loss in fragmented tropical forest is the greatest single threat to biodiversity. Fragmentation involves changes in the size, shape and spatial distribution of existing forest. Understanding these effects and comparing their impact with the influence of other environmental variables is of utmost importance in prioritising forest blocks for conservation. The spatial geometry of forest blocks in Ghana, West Africa, was examined with respect to tree species number and composition. Tree species number proved to be positively related to forest block area, according to laws of probability and ecological determinism. In addition, tree species composition was dictated by forest block size, with larger reserves recording significantly more rate species than smaller ones. Additional species encountered in reserves of increasing size followed a predictable pattern, which allowed the identification of species vulnerable to habitat loss. An effect of forest block shape on the structure and composition of tree species was visible using coarse spatial resolution satellite sensor imagery. Fragmentation of a previously continuous canopy led to distinct forest edge effects. This was verified by ground data, which showed an increase in the proportions of common pioneer species along reserve peripheries. Significant trends were only detected across small areas: indicating that shape is not an important consideration in the design of larger forest reserves. The effect of forest block proximity on tree species number was examined using regression analysis, but any rôle of proximity was dominated by the influence of area. The influence of climate and fire activity was strongly expressed throughout the examination of spatial geometry in the form of residual variation about the regression line. Results of multivariate analysis indicated that the management of size and disturbance should be considered in preference to shape and proximity if higher levels of diversity and bioquality are to be maintained.
5
Chappelka, Arthur H. "The combined effects of ozone, sulfur dioxide and simulated acid rain on the growth of three forest tree species". Diss., Virginia Polytechnic Institute and State University, 1986. http://hdl.handle.net/10919/74726.
Abstract (sommario):
Nine-week-old yellow-poplar and green and white ash were exposed to various concentrations of O₃ (0.00 to 0.15 ppm) and/or SO₂ (0.08 ppm), 4 hr/d, 5d/wk in combination with simulated rain (pHs 5.6, 4.3, 3.0), 1 hr/d, 2 d/wk, for 5 or 6 wk under controlled laboratory conditions. Pollutant exposures resulted in alterations in seedling biomass accumulation, growth rates, changes in carbon allocation among plant parts and modification in physiological processes associated with gas exchange. Ozone (0.010 ppm) and SO₂ together caused a significant decrease in height growth and biomass and an increase in leaf area ratio (LAR) in yellow-poplar. Ozone and SO₂ exposures resulted in linear decreases and increases, respectively, in root dry weight, leaf area increase, relative growth rates of all yellow-poplar plant parts and unit leaf rate with decreasing rain pH. Chlorophyll content increased in both O₃ and SO₂ treatments with increasing rain acidity. In green and white ash experiments height growth was inhibited by O₃, SO₂ and O₃ + SO₂ for green ash, whereas only leaf dry weight was decreased by O₃ exposure in white ash. Decreasing rain pH resulted in linear decreases in root/shoot ratio (RSR) and LAR, for white ash. In green ash, a quadratic response to rain pH occurred with these growth variables. Ozone and O₃ + SO₂-treated green ash exhibited a significant quadratic response in leaf weight ratio with increasing rain acidity. Leaf area ratio and RSR exhibited linear increases and decreases, respectively, for O₃ and rain acidity. In SO₂-treated white ash with increasing white ash and yellow-poplar seedlings exposed to various O₃ concentrations and simulated rain for 5 and 6 weeks, respectively, increasing O₃ concentrations caused linear decreases in height and biomass of white ash. Linear decreases in root growth rate and biomass and RSR occurred with decreasing rain pH, across O₃ treatments. Ozone (0.05 or 0.10 ppm) caused linear decreases in these variables in combination with increasing rain acidity. For yellow-poplar, increasing O₃ concentrations caused linear increases in RSR and specific leaf area. At 0.05 and 0.10 ppm O₃, stem and leaf biomass, their relative growth rates and leaf area all decreased with decreasing rain pH. Ozone (0.10 ppm) exposure caused a decrease in stomatal conductance, and decreasing variable. rain pH resulted in a linear decrease in this A linear decrease in net photosynthesis also occurred with increasing rain acidity in O₃-treated (0.10 ppm) plants. These results demonstrate that gaseous pollutants in combination with simulated acid rain can have detrimental effects on growth of three forest tree species, under controlled laboratory conditions.Ph. D.
6
Schaap, James Cornelis. "Nitrogen fertilization and tree species effect on the soil microbial communities and consequences for soil carbon". Thesis, University of Canterbury. School of Biological Sciences, 2011. http://hdl.handle.net/10092/6582.
Abstract (sommario):
In the face of ever increasing atmospheric CO₂ a better understanding of soil properties and processes and the effect of management practices, such as the application of nitrogen fertilizer is of importance and could potentially improve our ability to sustainably manage forestry systems. With that in mind this study was conducted in order to investigate the effects of tree species and fertilization on soil carbon and the soil microbial community. To this end, soil from fertilized and unfertilized plots at Berwick forest, under stands of Pinus radiata and Sequoia sempervirens at Hanmer and under six different tree species at Holt forest was sampled. Two glasshouse pot trials were established using soil collected from the Hanmer and Berwick forest sites and seedlings of Pinus radiata, Sequoia sempervirens, and Eucalyptus nitens were grown.
Soil properties were determined from both the field sites and pot trials including soil organic matter, carbon, nitrogen, and microbial biomass by chloroform fumigation extraction. Biolog ecoplates were used to determine the relative differences in diversity based on substrate utilization patterns of the soil microbial communities in soil sampled from the glasshouse pot trials.
Soil microbial biomass carbon, nitrogen and the ratio of microbial biomass carbon:nitrogen differed significantly between Pinus radiata and the other tree species sampled at Holt forest. Significant effects of fertilization and tree species on soil carbon and microbial biomass were observed in both pot trials. Soil carbon differed significantly between Eucalyptus nitens and both Pinus radiata and Sequoia sempervirens in the first pot trial and relative to both, E. nitens contributed significantly more carbon. No significant effect of either fertilization or tree species on the catabolic diversity of the soil microbial community in both glasshouse pot trials was observed. The results demonstrated the effects that fertilization and tree species can have. Particularly notable was the short-time period in which tree species effects became apparent coupled with the absence of any aboveground inputs to the soil.
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Diaz, Alexander P. "Effect of Diaprepes root weevil on leaf gas exchange and growth of select ornamental tree species". [Gainesville, Fla.] : University of Florida, 2005. http://purl.fcla.edu/fcla/etd/UFE0011363.
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Beggs, Margaret Ann. "The effect of different tree species on through fall and soil solution chemistry at Gisburn Forest". Thesis, University of Aberdeen, 1991. http://digitool.abdn.ac.uk/R?func=search-advanced-go&find_code1=WSN&request1=AAIU078985.
Abstract (sommario):
A study was carried out to investigate the effect of four tree species on the acidity and chemistry of rainwater as it passed down the forest profile. The four species, Norway spruce (Picea abies), Scots pine (Pinus sylvestris), oak (Quercus petraea) and alder (Alnus glutinosa) were all at the same site at Gisburn (Bowland Forest), north-west England. The water was collected as rain, beneath the canopy and the forest floor, at the boundary of the A and B horizons and within the B horizon. The water was collected and analysed for pH, PO43--P, NO3--N, NH4+-N, Cl, SO42--S, Na+, Ca2+ and Mg2+ every two weeks. There were occasional analyses for aluminium. Porous ceramic cups were used to collect water in the soil horizons and so volumes had to be estimated. A further correction had to be made to allow for the loss of water as runoff over the surface of the forest floor. There were consistent differences between the species. The species differed in both the processes responsible for and the location of the production of acidity. Under all species there was a great reduction in acidity in the deep soil horizons. The source and nature of the anion thought to be associated with cation leaching also differed under the species. Most of the species differences could be attributed to processes occurring in the forest floor. Of most importance were: the fixation of atmospheric nitrogen by alder and its subsequent release as NO3--N; the rate of decomposition of the various litters; and the horizon where most root uptake occurred. The differences observed in the throughfall were not reflected in the forest floor or soil horizons. There was no evidence of depletion of cations in the mineral soils after thirty years of tree growth but it was considered that the risk was greater under alder and pine than under spruce and least under oak.
9
Redwood, Mame S. "The Effect of Silviculture Management on the Spread of Three Invasive Species". Ohio University / OhioLINK, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1337273012.
10
Chen, Hsiang Ling. "Barrier Effects Of Roads And Traffic On Animal Occurrence, Space Use, And Movements". Diss., The University of Arizona, 2015. http://hdl.handle.net/10150/555947.
Abstract (sommario):
Habitat fragmentation and destruction caused by linear infrastructure, including roads, railways, and power line corridors, are recognized as major threats to biodiversity around the world. Roads can act as barriers by impeding animal movement and restricting animal space use. An understanding of factors that influence barrier effects is important to discern the impacts of habitat fragmentation and to develop appropriate mitigation. The barrier effects of roads are driven by several distinct but not mutually exclusive mechanisms that include traffic, edge, and gap avoidance. We used an endangered forest obligate, the Mount Graham red squirrel (Tamiasciurus hudsonicus grahamensis), as our study organism to assess effects of traffic noise on animal occurrence and demonstrated that traffic noise had spatially extensive and negative effects on site occupancy after accounting for effects of distance from roads and the environment. We investigated barrier effects of forest roads and assessed effects of traffic, road edges, and canopy gaps on space use of Mt. Graham red squirrels and compared to the response of introduced, edge-tolerant Abert's squirrels (Sciurus aberti). Forest roads acted as partial barriers for red squirrels regardless of traffic volume likely due to avoidance of canopy gap created by roads, whereas Abert's squirrels showed no avoidance of roads. Therefore, roads restricted movement and space use of a native forest-dependent species while creating habitat preferred by an introduced, edge-tolerated species. Through a meta-analysis of studies that quantified road crossing behavior by mammals, we found that all types of roads, from major highways to narrow forest roads, can impede movement for certain species of mammals. Magnitude of barrier effects of roads decreased as species body mass increased, and was affected positively by increasing road width. We suggest that the species-specific magnitude of barrier effects of roads may be anticipated with basic information from life history traits and road characteristics that are readily accessed through open resources or easily measured.
11
Getachew, Girma. "Tannins in tropical multipurpose tree species : localisation and quantification of tannins using histochemical approaches and the effect of tannins on in vitro rumen fermentation /". Stuttgart : Ulrich E. Grauer, 1999. http://bvbr.bib-bvb.de:8991/F?func=service&doc_library=BVB01&doc_number=009095947&line_number=0001&func_code=DB_RECORDS&service_type=MEDIA.
12
De, Ridder Cornelius Henry. "The effect of Acacia karroo tree density on grass species composition, forage yield and quality in different rainfall regimes in the Eastern Cape, South Africa". Thesis, Nelson Mandela Metropolitan University, 2016. http://hdl.handle.net/10948/2858.
Abstract (sommario):
It is widely believed that Acacia karroo Hayne trees compete with and negatively affect the production of grasses in their immediate surroundings. This perception formed as a result of observations by farmers of their veld as well as some research. The complexity of plant interactions in different conditions required that research be done to better explain the extent of grass and tree interactions. In response to this need, the effect of a range of Acacia karroo densities on grass production was tested in areas of differing rainfall. Results emphasize the complexity of such plant interactions but highlight rainfall as influencing the effect of tree density on grass production and grass quality. Study sites were chosen with significant differences in tree density and rainfall and this was found to be concomitant with significant differences in grass yield and crude protein (p < 0.001). Grass yield (mass produced) was negatively correlated with tree density (p < 0.001) and was affected by rainfall. High tree density reduced grass yield at the lower rainfall sites, but a reduction in yield was only recorded during dry conditions in the higher rainfall areas. By contrast, the crude protein content of grasses was positively correlated to tree density (p < 0.001). However, as with yield, rainfall played an important part in the strength of the correlation. Soil properties such as temperature (-) (p = 0.011), phosphorus content (+) (p = 0.006), calcium concentration (+) (p = 0.005), acid saturation (-) (p = 0.018), and soil pH (+) (p = 0.008) were also significantly correlated to tree density. Tree density enriched the soil, subsequently benefitting grass quality. The study sites investigated, had different plant communities and environmental conditions with Cradock, Kubusi Drift and Kei Mouth having unique communities and conditions while Adelaide and Cathcart could not be separated in either. Cradock was the driest site and the vegetation was dominated by both grasses and karroid shrubs, differing in pattern and process from the other sites. The Kubusi Drift site had high tree densities, to the extent that the trees altered the grass species composition. The effects of rainfall on grass yield and quality exceeded that of community composition differences.
13
Uzakbaeva, Jyldyz. "Effect of different tree species on soil quality parameters in forest plantations of Kyrgyzstan Einfluss verschiedener Baumarten auf die Parameter der Bodenqualität unter Aufforstungen in Kirgisien /". [S.l. : s.n.], 2005. http://deposit.ddb.de/cgi-bin/dokserv?idn=974376329.
14
Kübler, Daniel Peter [Verfasser], Reinhard [Akademischer Betreuer] Mosandl, Thomas [Gutachter] Knoke e Reinhard [Gutachter] Mosandl. "Effect of topography on the distribution of tree species and radial diameter growth of potential crop trees in a tropical mountain forest in southern Ecuador / Daniel Peter Kübler ; Gutachter: Thomas Knoke, Reinhard Mosandl ; Betreuer: Reinhard Mosandl". München : Universitätsbibliothek der TU München, 2020. http://d-nb.info/1220320145/34.
15
Clesse, Margaux. "Étude multi-sites de la réponse de la fertilité chimique des écosystèmes forestiers dans un contexte de changements (dépôts atmosphériques et substitution d’essences)". Electronic Thesis or Diss., Université de Lorraine, 2023. http://www.theses.fr/2023LORR0009.
Abstract (sommario):
Les écosystèmes forestiers se développent souvent sur des sols acides et pauvres en nutriments. Dans de nombreuses régions, les dépôts atmosphériques acides élevés (acides sulfurique et nitrique) ont considérablement accéléré l'acidification des sols et des eaux de surface au cours de la seconde moitié du XXe siècle, entraînant fréquemment une dégradation de la fertilité des sols et le déclin des forêts. En sus, la sélection et/ou la substitution d'essences par la gestion forestière peuvent également avoir un effet important sur le fonctionnement biogéochimique des sols et des écosystèmes forestiers. Dans ce contexte, leur durabilité est remise en question et il est nécessaire de quantifier l'évolution de la fertilité chimique des écosystèmes forestiers face à ces pressions et de mieux comprendre leur fonctionnement biogéochimique, afin d'assurer une gestion durable des forêts. Les objectifs principaux de cette thèse sont de i) quantifier l'évolution de la fertilité chimique d'écosystèmes forestiers en utilisant quatre méthodes de diagnostic : ré-échantillonnage du sol, suivi des solutions de sol, des concentrations foliaires et calcul du bilan « entrées-sorties », ii) comprendre les mécanismes sous-jacents à cette évolution et iii) comparer les diagnostics obtenus par les différentes méthodes, en prenant en compte l'incertitude autour du bilan. Pour cela, nous avons quantifié l'évolution de la fertilité sur une période de 20 à 30 ans par ces 4 méthodes, sur des placettes monospécifiques du site de Breuil-Chenue et sur 8 placettes de niveau III du réseau RENECOFOR. Les résultats ont souligné que l'essence avait un effet sur l'acidification des sols et sur les réserves de cations nutritifs échangeables du sol. Les feuillus semblent acidifier moins intensément les sols que les résineux. Une restauration du pH est observée sous le chêne et le hêtre alors que l'acidification semble se poursuivre sous les résineux, notamment sous le Douglas et le pin et encore plus sous le sapin et l'épicéa. Une acidification des sols et les pertes de nutriments associés ont aussi été mises en évidence sur certains sites RENECOFOR. Le nitrate et le sulfate semblent être les principaux moteurs de l'acidification. Leur origine dépend cependant du site étudié : ils sont parfois issus des dépôts atmosphériques actuels mais des sources internes à l'écosystème peuvent également intervenir via une nitrification excédentaire (surtout sous le Douglas, le pin, le chêne à Breuil et CPS 77) ou une désorption de S dans le sol (surtout sur les sites RENECOFOR). La lixiviation du S et du N et celle des cations associés a tendance à acidifier les sols. Toutefois, la réponse des sites face à l'acidification peut varier, notamment en fonction de la prédominance soit du cycle biologique soit du cycle géochimique. Les sites identifiés avec un cycle géochimique prépondérant (CHS 41, CPS 77, HET 30 et SP 38) ont des réserves en nutriments soutenues davantage par les flux d'altération et de dépôts atmosphériques, alors que ceux dominés par le cycle biologique (EPC 08, EPC 87, PS 67a, SP 57) ont des pools de nutriments renouvelés surtout par les flux de recyclage. Enfin, les résultats ont montré que la comparaison entre les différentes méthodes de diagnostic de fertilité n'est pas aisée. Des écarts dans les diagnostics ont été mis en évidence, avec des résultats parfois contradictoires. La prise en compte de l'incertitude autour du bilan n'explique pas à elle seule les écarts observés avec l'approche par ré-échantillonnage du sol. L'incertitude de choix de modèle pourrait peut-être en partie expliquer l'origine des divergences. Ces travaux mettent en évidence l'importance de continuer les recherches engagées sur i) la compréhension de la réponse des écosystèmes forestiers face aux changements de dépôts atmosphériques et de substitution d'essences et ii) l'évaluation des incertitudes autour des différentes approches de diagnostic de fertilitéForest ecosystems often grow on acidic, nutrient-poor soils. In many places, high acidic atmospheric deposition (sulfuric and nitric acids) has significantly accelerated the acidification of soils and surface waters during the second half of the 20th century, frequently leading to soil fertility degradation and forest decline. In addition, species selection and/or substitution by forest management can also have a significant effect on the biogeochemical functioning of soils and forest ecosystems. In this context, their sustainability is questioned and it is necessary to quantify the evolution of the chemical fertility of forest ecosystems in the face of these pressures and to better understand their biogeochemical functioning, in order to ensure sustainable forest management. The main objectives of this thesis are i) to quantify the evolution of chemical fertility of forest ecosystems using four diagnosis methods: soil resampling, monitoring of soil solutions, foliar concentrations and calculation of the "input-output" budget, ii) to understand the mechanisms underlying this evolution and iii) to compare the results obtained by the different methods, taking into account the uncertainty surrounding the budget. To do this, we quantified the evolution of fertility over a period of 20 to 30 years by these 4 methods, on monospecific plots of the Breuil-Chenue site and on 8 level III plots of the RENECOFOR network. The results showed that the species had an effect on soil acidification and on the pools of exchangeable nutritive cations in the soil. Hardwoods appear to acidify soils less intensely than coniferous. A restoration of pH is observed under oak and beech, whereas acidification seems to continue under coniferous, especially under Douglas fir and pine, and even more under Nordmann fir and spruce. Soil acidification and associated nutrient losses have also been demonstrated on some RENECOFOR sites. Nitrate and sulphate seem to be the main drivers of acidification. However, their origin depends on the site studied: they are sometimes derived from current atmospheric deposition, but internal sources to the ecosystem may also intervene via excess nitrification (especially under Douglas fir, pine, oak at Breuil and CPS 77) or desorption of S into the soil (especially on RENECOFOR sites). Leaching of S and N and associated cations tends to acidify soils. However, the response of sites to acidification can vary, depending on the predominance of either biological or geochemical cycling. Sites identified with predominant geochemical cycling (CHS 41, CPS 77, HET 30, and SP 38) have nutrient pools supported more by weathering and atmospheric deposition fluxes, whereas the sites dominated by biological cycling (EPC 08, EPC 87, PS 67a, SP 57) have nutrient pools supported primarily by recycling fluxes. Finally, the results showed that the comparison between the different fertility diagnosis methods is not easy. Differences were highlighted, with sometimes contradictory results. Taking into account the uncertainty around the budget does not alone explain the differences observed by the soil resampling approach. Uncertainty in the choice of model could perhaps partly explain the origin of the discrepancies. This work highlights the importance of continuing research on i) understanding the response of forest ecosystems to changes in atmospheric deposition and species substitution and ii) assessing the uncertainties surrounding the different approaches to fertility diagnosis
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Morath, Simon. "Effects of tree species diversity on insect herbivory". Thesis, Royal Holloway, University of London, 2013. http://repository.royalholloway.ac.uk/items/916c671f-79af-41eb-99b1-df69faa84961/1/.
Abstract (sommario):
It is generally believed that tree species growing in mixed forest stands are less susceptible to insect herbivore damage than if grown in monocultures, but previous studies have been largely observational and focussed mainly on tree species richness effects. In this thesis, I examined effects of three components of forest diversity (tree species richness, intraspecific genotypic diversity and functional diversity) on insect herbivores using three long-term forest diversity experiments in Finland and Germany. I have also explored the sources of variation in and the mechanisms behind the effects of tree diversity on insect herbivores. I found that all three components of forest diversity significantly influenced insect herbivore abundance and damage. Tree species richness effects depended on the insect herbivore feeding guild, but also changed within season and between years. As a result, silver birch (Betula pendula) experienced both associational resistance (reduced damage in mixed stands) and associational susceptibility (higher damage in mixed stands) to different insect herbivores and in some instances this altered temporally. In contrast, tree species richness effects on insect herbivory were spatially consistent and not mediated by tree size (physical apparency), physical properties of leaves or natural enemies. Interestingly, tree species richness and genotypic diversity had opposite effects on leaf miners; leaf miner abundance and species richness were lower in species-rich stands, but higher in mixtures containing several genotypes of silver birch. To test the effects of tree functional diversity, I created a functional diversity index based on constitutive emissions of monoterpenes and isoprene by different tree species and showed that tree species which emitted low levels of volatiles experienced associational resistance in stands with high diversity of volatile emissions. This suggests that increasing chemical complexity in mixed stands may interfere with host finding ability of herbivores.
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Ribbons, Relena Rose. "Seeing the forest for the trees : tree species effects on soil microbial communities and nutrient cycling dynamics". Thesis, Bangor University, 2017. https://research.bangor.ac.uk/portal/en/theses/seeing-the-forest-for-the-trees-tree-species-effects-on-soil-microbial-communities-and-nutrient-cycling-dynamics(f3ddf30e-c126-4345-b388-4384cfc8d617).html.
Abstract (sommario):
Tree species influence soils above and belowground communities through leaf litter and root inputs. Soil microbial communities can directly influence tree growth and development through processes such as decomposition of leaves, and indirectly through chemical transformation of nutrients in soils as an influence of altered C:N ratios due to leaf litter and root inputs. This thesis aims to document some of the mechanisms by which trees influence soil microbial communities and nitrogen cycling processes like gross and net ammonification and nitrification. This thesis also aims to determine the role of site nitrogen status in modulating those tree species effects. The effects of tree species on ammonification and nitrification rates in forest floors and mineral soils were explored, and related to functional genetic markers for ammonia-oxidation by archaea and bacteria (amoA AOA and AOB), bacterial denitrification (nirS and nirK), and the general markers for bacteria (16S) and fungi (ITS). Two paired high-resolution laboratory methods were used to investigate the relationships between trees, soils, and the microbial communities, including molecular techniques such as quantitative polymerase chain reaction (qPCR) to target gene abundances in soils, and 15N pool-dilution experiments to understand how ammonium and nitrate are produced and consumed in soils. Soil samples were collected from two common garden experiments, named EP571 in Canada (Ribbons et al. 2016), and in Denmark, and both 15N and qPCR-based techniques were used to determine tree species effects and attribute N cycling processes to the abundances of functional genes. At EP571, western red cedar (Thuja plicata) forest floor nitrogen transformation rates differed from Douglas-fir (Pseudotsuga menziesii), Sitka spruce (Picea sitchensis), and western hemlock (Tsuga heterophylla), which corresponded with western red cedar having highest abundances of bacterial 16S and amoA AOA genes. A manipulative mesocosm (the Rhizotron) in Wales was used to determine how mixtures and monocultures of seedling species influenced tree growth, soil physical properties and soil microbial community structure and function within the first three years of growth. Within the Rhizotron experiment both alder (Alnus rubra) and Douglas-fir grew taller when grown in mixtures compared with monocultures of each species. Sycamore maple (Acer pseudoplatanus) acquired slightly greater aboveground biomass when planted in mixtures with common oak (Quercus robur), which attained less biomass in mixtures than monocultures. C:N ratios of leaves, stems, roots, and rhizospheric soils were determined to see if mixtures influenced C:N in trees. Rhizospheric soil microbial communities (including bacterial and fungal markers and the 4 genes tied to N cycling) were compared among the 4 tree species in the Rhizotron. Soil samples for microbial analyses were collected before seedlings were planted, and just before the experiment was harvested. These data show differences in height, biomass and C:N ratios between species can be observed at a seedling growth stage, but microbial communities may require longer exposure to develop. Lastly, the Bangor Diverse experiment was used to further explore diversity and mixture effects on soil microbial communities and N transformations. We found few mixture or monoculture tree species effects on mineral soil microbial communities or net nitrification or ammonification rates. Collectively, these stories shed light on the important functional role of soil microbes in forest soil N cycling. This thesis also highlights the use of isotope and microbial techniques for parsing out relationships between site, tree species identity and ecosystem functions, with the largest links observed between gross ammonification and microbial communities.
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Liese, Rebecca [Verfasser], Ina Christin [Akademischer Betreuer] Meier, Ina Christin [Gutachter] Meier, Andrea [Gutachter] Carminati, Hermann [Gutachter] Behling, Michaela [Gutachter] Dippold, Markus [Gutachter] Hauck e Stefan [Gutachter] Scheu. "The effect of the mycorrhizal type on root-rhizosphere interactions in AM and ECM tree species: field studies and mesocosm experiments / Rebecca Liese ; Gutachter: Ina Christin Meier, Andrea Carminati, Hermann Behling, Michaela Dippold, Markus Hauck, Stefan Scheu ; Betreuer: Ina Christin Meier". Göttingen : Niedersächsische Staats- und Universitätsbibliothek Göttingen, 2019. http://d-nb.info/1178792072/34.
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Liese, Rebecca [Verfasser], Ina Christin [Akademischer Betreuer] Meier, Ina Christin Gutachter] Meier, Andrea [Gutachter] [Carminati, Hermann Gutachter] Behling, Michaela [Gutachter] Dippold, Markus [Gutachter] [Hauck e Stefan [Gutachter] Scheu. "The effect of the mycorrhizal type on root-rhizosphere interactions in AM and ECM tree species: field studies and mesocosm experiments / Rebecca Liese ; Gutachter: Ina Christin Meier, Andrea Carminati, Hermann Behling, Michaela Dippold, Markus Hauck, Stefan Scheu ; Betreuer: Ina Christin Meier". Göttingen : Niedersächsische Staats- und Universitätsbibliothek Göttingen, 2019. http://nbn-resolving.de/urn:nbn:de:gbv:7-11858/00-1735-0000-002E-E59D-C-2.
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Liu, Tengjiao. "Effects of Climate Change and Local Environmental Factors on Long Term Water Use Efficiency and Tree Growth in Different Forest Ecosystems". Thesis, Griffith University, 2021. http://hdl.handle.net/10072/407567.
Abstract (sommario):
Background Climate change has become one of the significant global challenges confronting all the people in the world. Climate change, particularly rising atmospheric carbon dioxide (CO2) concentration (ca) and temperature, and changes in water availability have also affected tree growth of forest ecosystems worldwide. Several studies about the effects of climate change on tree growth and physiological responses have been reported. However, these are mostly based only on experiments with isolated trees or seedlings grown under intensive and short-term exposure to one or two climatic factors. Since long-term and gradual impacts of climate change on tree growth and physiological responses could be different from the short-term effects, there is an urgent need to investigate how tree species respond to elevated atmospheric CO2 and temperature and water availability changes at larger scales and over more extended periods.
This study is complicated because tree growth rates vary among genotypes and change as trees age and because climatic conditions, such as temperature, precipitation and humidity, and atmospheric CO2, have been changing over time. There are also indications that tree responses to climate change may change with time as the trees grow. Moreover, since tree growth (biomass) is a product of physiological processes, the physiological processes are affected by the structure of the organs or tissues where the processes occur. In turn, the structures of the organs are determined by the products of the previous physiological processes. To understand the mechanisms on how long-term climate change affects tree physiological processes and growth, we have to understand the relationships among the climate, tree growth and physiological responses, and how long tree growth trend will remain alongside the elevating CO2 concentration before it declines, considering that the forest ecosystems are one of the most important contributors to the global CO2 assimilation, which can effectively counteract the global warming.
Hypothesis and objective My research has been focused on studying the long-term tree growth and water use efficiency in response to rising atmospheric CO2 concentration, in combining with other environmental factors, and their influences on climate change in the future. I hypothesised that tree growth is affected by biological effects, such as tree species and ages, and non-biological effects, namely locations, temperature, precipitation and humidity. Thus, all my experiments' main objectives were to confirm my hypothesis and quantify how those biological and non-biological factors would influence tree growth and water use efficiency in the context of both spatial and temporal scales. The goals and objectives of this research were:
To determine the effect of long-term climatic conditions on tree growth and physiological processes. The objectives were to determine how climatic factors would influence tree growth and physiological responses; to determine the key climatic controls of the change in tree growth and physiological responses, and determine how each of the key climatic factors and their interactions affect tree growth and physiological responses.
To determine the variation of the climate-tree relationship among tree species. The objective was to determine the phenotypic and genotypic variation of the effects of climate change on tree growth and physiological responses among tree species,
To determine the acclimatization of tree species in response to climate change. The objectives were to determine the responses of tree species to climate change over time and determine tree species' responses to climate change before and after they are exposed to specific climatic conditions.
Materials and methods To achieve the objectives, tree ring technologies were adopted. Trees record relevant information in their annual rings, represent important natural archives of climate changes, and provide archives of tree growth responses to the past climate variation. With tree ring width growth, information from tree-ring stable isotope compositions were used to better understand the dynamic relationships among the climate, tree growth, and physiological responses.
My current research was commenced with seven tree species sampled from five different forests in China, covering both subtropical and boreal climatic conditions. The long-term tree-ring chronology was established by applying tree ring width measurement and cross-dating verified by COFECHA program; therefore, the basal area increments (BAI) were calculated sequentially. Meanwhile, the intrinsic water-use efficiency (iWUE) was calculated by measuring carbon isotope composition (δ13C) in tree ring samples. Tree ring δ13C relationships with BAI and atmospheric CO2 concentration were also quantified.
Results and discussion From this study, we have gained further understanding of the relationships among long-term climate change, tree growth and physiology, as a basis for future projection of silvicultural manipulations under different climate change scenarios.
In Chapter 2, both BAI values of the two tree species (Pseudolarix amabilis and Cryptomeria japonica, sampled from a subtropical monsoon forest located in eastern China), continuously increased with the rising of CO2 concentration until the atmospheric CO2 concentration tipping points were reached (the tipping points of Pseudolarix amabilis and Cryptomeria japonica were in year 1997 and 1996 when atmospheric CO2 concentration reached 365.1 ppm and 636.0 ppm respectively), after which tree growth started to decline with the rising CO2, while iWUE exerted a continuous increase trend with the increasing CO2 concentration.
In Chapter 3, the results showed a decreasing trend in relative humidity over the past 70 years in a subtropical forest of south-east China with rising CO2 concentrations and temperature and the initial increasing tree growth for both Pinus massoniana and Cryptomeria japonica from the rising CO2, which peaked when CO2 concentration reached 330 ppm and 385 ppm in year 1974 and 2008 respectively, but decreased thereafter with increasing water limitation. Tree iWUE showed the same continuing increase trend as the two species in Chapter 2.
In Chapter 4, three tree species (Cinnamomum micranthum, Pinus massoniana and Cunninghamia lanceolata) were sampled in two nearby subtropical forests of south-east China. The tree-growth also initially increased with the rising Ca, then decreased with the increasing Ca. The tipping points among the three species slightly varied but all happened between year 1995 and 1999. In addition, iWUE continuously increased with the rising Ca regardless the tipping points of BAI with the Ca.
In Chapter 5, two species (Larix gmelinii Rupr and Betula platyphylla) were sampled in a boreal forest of north-east China, the results were similar to the previous chapters, while iWUE showed consistent increase during the entire growth period for both species, BAI reached the tipping points when Ca reached 366 ppm in year 1998 for Larix gmelinii Rupr, and 353.5 ppm in year 1989 for Betula platyphylla.
In summary, the experimental results demonstrated that tree growth of BAI showed a continuous increase among all sampled tree species with the rising CO2 concentration until the CO2 concentration tipping points were passed. The trees’ responses were both species and site dependent. After reaching the critical points, tree growth started to decline even with the rising CO2 concentration, while iWUE exerted a continuously increasing trend with the increasing CO2 concentration, which biologically proofed that the decreased BAI was not dominated by tree age, but due to the rise of Ca and warming induced water limitation.
The series of tree ring studies reported in this thesis has highlighted that there would be non-linear tree growth responses to the increasing Ca of the tree species in both subtropical and boreal forests, with the initial increases in tree growth detected as the atmospheric CO2 increased, but the tree growth peaked when the critical tipping points of Ca were reached and then declined thereafter. However, tree WUE continued to increase with the rising Ca, initially due to the increasing photosynthesis and tree growth, then later due to the warming induced water limitation. Unfortunately, the tipping points of Ca for tree species in both subtropical and boreal forests were reached between 1974 and 2008, and tree growth decreased with the rising Ca once the CO2 tipping points were passed, leading to a positive feedback to climate change.Thesis (PhD Doctorate)
Doctor of Philosophy (PhD)
School of Environment and Sc
Science, Environment, Engineering and Technology
Full Text
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Hood, Lorraine A. "Effects of pathogenic and mycorrhizal fungi on regeneration of two tropical tree species". Thesis, University of Aberdeen, 2002. http://digitool.abdn.ac.uk/R?func=search-advanced-go&find_code1=WSN&request1=AAIU151993.
Abstract (sommario):
This thesis tests the hypothesis that the influence of fungal pathogens and arbuscular mycorrhizal (AM) fungi varies in response to proximity to parent trees and light environment to affect seedling establishment in two tree species, Milicia regia and Antiaris toxicaria, in Ghanaian tropical rain forest. Both species are from the same family (Moraceae) yet they differed markedly in their degree of susceptibility to disease and AM infection. Milicia regia seedlings were highly vulnerable to disease (caused mainly by Oomycetes, particularly Phytophthora species) and exhibited high levels of mycorrhizal colonisation, whereas Antiaris toxicaria seedlings suffered no mortality due to disease and had very low levels of AM colonisation in all forest situations. This species was, however, more susceptible to predation, the intensity of which depended on proximity to conspecifics. Spatial patterns of disease were evident in Milicia regia: seedlings had a higher probability of incurring pathogen-induced mortality close to female trees than under male trees or at a distance from parents, and were less susceptible to disease in light gap conditions. It is possible that spatial patterns in seedling disease were due to negative feedback resulting in higher inoculum loads of soil-borne Oomycetes under female trees. Differences in disease occurrence in contrasting light conditions were due to increased resistance of the host in gaps as opposed to differential pathogen activity. AM colonisation also varied spatially, with seedlings displaying host-specific inoculum preference. Moreover, AM colonisation also varied in response to light environment, being higher in gap conditions. It is proposed that a continuum of mycorrhizal benefit exists for Milicia regia - from improved nutrition to protection against pathogens, with the type of benefit being highly dependent on light environment. Milicia regia regeneration is thus subject to complex interactions between pathogens, mycorrhizal fungi and light environment which vary spatially around conspecifics, whereas these processes have limited influence on Antiaris toxicaria seedlings. Implications for patterns of seedling regeneration and the maintenance of tropical forest species diversity are discussed.
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Healy, Chrystal. "The biodiversity-ecosystem functioning relationship : separating the effects of species richness, from those of species identity and environmental heterogeneity in a tropical tree plantation". Thesis, McGill University, 2007. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=101136.
Abstract (sommario):
This study attempts to expand existing knowledge on the relationship between biodiversity and ecosystem functioning, by studying a four year old tropical tree plantation. The growth of trees coming from monocultures, three species mixtures and six species mixtures was compared. Through multivariate statistical analysis, the variation in tree productivity was partitioned into different components: variation explained by (1) species richness, (2) species identity and (3) the environment. Results reveal that the environment explains the largest portion of variability in tree growth. Moreover, of the small amount of variation explained by diversity, species identity is found to be twice as important then species richness. Of notable significance was the amount of variation explained by the interaction of diversity with the environment.
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Catry, Filipe Xavier. "Fire effects on forest species in mediterranean basin ecosystems: ecology and management". Doctoral thesis, ISA, 2013. http://hdl.handle.net/10400.5/6151.
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Solberg, Bård Øyvind. "Effects of climatic change on the growth of dominating tree species along major environmental gradients". Doctoral thesis, Norwegian University of Science and Technology, Department of Biology, 2002. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-487.
Abstract (sommario):
This thesis deals with effects of climate on tree growth of the dominating conifer species, Picea abies (L) Karst. (Norway spruce) and Pinus sylvestris L (Scots pine), in central Norway and Fennoscandia. Both species are sampled along major environmental gradients, i.e. altitude and oceanicity, and growth responses to climate, i.e. temperature and precipitation, are examined along these gradients. Additionally, time is considered as an environmental gradient and temporal responses are carefully deciphered. Special attention is given to large-scale climate oscillation and their effect on tree growth. In the individual papers the specific aims have been to:
1. identify climate variables (all seasons) with significant influence on radial tree growth of P. abies and P. sylvestris along major environmental gradients (Paper I-IV)
2. identify if and how the growth response to climate has changed through time along these gradients (Paper I-IV)
3. make interregional comparisons of P. sylvestris growth pattern across Fennoscandia from oceanic western Norway to continental eastern Finland (Paper III)
4. analyse to what degree large-scale circulation patterns of air masses are registered in regional tree growth of both P. abies and P. sylvestris (Paper I, III and IV)
5. discuss possible effects on radial tree growth of a predicted warmer climate (Paper I, III and IV)
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Fernandes, Miguel V. "Effects of Changes in the Everglades on Two Indicator Species: Sigmodon Hispidus and Oryzomys Palustris". Scholarly Repository, 2011. http://scholarlyrepository.miami.edu/oa_dissertations/606.
Abstract (sommario):
The Everglades, a wetland ecosystem unique to southern Florida has been degraded by the loss of nearly half of its area to urban and agricultural development as well as by alterations to Florida’s hydrology. Modifications to the flow of water to the Everglades have altered the remaining portion of the Everglades. Most prominent among these changes in the remaining Everglades is the loss of tree islands with a disproportionately greater loss of larger tree islands. Despite their significance as “keystone habitats”, our understanding of how changes to Everglades tree islands will affect fauna is poor. In the work presented, 16 study tree islands of Rock Reef Pass, Everglades National Park, Homestead, FL, were classified into three size classes (large, medium and small) and used animal capture histories collected between February 1994 and December 2005 to investigate the relationship between tree island size classes and indirect indicators of adult female hispid cotton rat (Sigmodon hispidus) and marsh rice rat (Oryzomys palustris) fitness and reproduction. Adult female S. hispidus and O. palustris body weights were used as an indicator of adult female fitness and compared among tree island size classes. The proportions of reproductively active females, the proportions of captures of individuals in the juvenile age class and the number of juveniles per female were used as indirect indicators of female reproduction and compared among island size classes. Animal capture histories were also used to perform multi-state mark-recapture analyses, where sates were defined as three island size classes, to draw inferences about state-specific rates of survival and state transition probabilities for Oryzomys palustris and Sigmodon hispidus as a function of the most salient features of the Everglades ecosystem, namely, its tree islands and its seasonal wet and dry periods. Specifically, Akaike’s, information criterion (AIC) was used to make inferences about factors influencing survival and transition probabilities by comparing the relative fit among models where survival and transition rates are described as functions of tree island size classes and as a function of environmental variables that distinguish seasonal periods (monthly water levels, total monthly rainfall, mean air temperature, days dry, days inundated). The probabilities of individuals remaining within the same island size class were interpreted as an indirect indicator of size-class specific tree island use. Results indicated that greater proportions of S. hispidus adult females were reproductively active and had higher fitness on larger islands than females on smaller islands. The body weights of S. hispidus adult females, the proportions of individuals in the juvenile age class and the number of juveniles per female, were positively correlated with tree island area while the proportions of reproductively active S. hispidus females were not. When compared among tree island size classes, S. hispidus females recaptured on the same large island weighed more than females recaptured on the same and medium or small island suggesting that females with greater fitness are found on larger tree islands. The proportions of reproductively active S. hispidus females and of individuals in the juvenile age class were greater on larger tree islands than on smaller islands, although the number of juveniles per females did not differ among tree islands. The results also indicated that differences in the fitness and reproductive condition of O. palustris females are not as distinct among females on different size tree islands. The body weights O. palustris adult females, the proportions of juveniles and the number of juveniles per female were not correlated with island area, while the proportions of reproductively active females were negatively correlated with tree island area. The body weights of O. palustris adult females recaptured on the same large tree island were higher than those of females on smaller islands while the proportions of females that were reproductively active and the proportions of captures of juveniles were higher on small islands than on large islands. Mark-recapture analysis provided evidence that overall, Sigmodon hispidus survival rates were higher on larger islands than on smaller islands. Evidence was not found that Oryzomys palustris survival rates differed among size classes, perhaps due to the limited spatial scale of this study relative to the spatial sale of O. palustris habitat use. Both species’ survival probabilities differed between seasons with Oryzomys palustris having higher survivorship during wet seasons and Sigmodon hispidus during the dry season. Both Oryzomys palustris and Sigmodon hispidus were more likely to remain on large island than on smaller islands.
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Baptista, Mariana Dias. "Use of different street trees species and their effect on human thermal comfort". Universidade de São Paulo, 2014. http://www.teses.usp.br/teses/disponiveis/11/11150/tde-10112014-092618/.
Abstract (sommario):
The continuous transformation in urban areas has brought many problems related to the loss of environmental quality, such as the lack of trees in the streets. It is commonly understood that urban forestry influences directly on thermal comfort in urban areas, and people can actually feel the different environmental conditions between a street with and without trees in a city. That is why better management of the trees can benefit local environmental quality, and, consequently, the quality of life of its population. One of the first steps of this management is the choice of species, but few studies approach the real effect of this choice for future local environmental conditions. The present work aims at investigating the effect of using different species in urban forestry for thermal comfort in Piracicaba - Sao Paulo. In order to do so, instruments were used to measure the air temperature, relative humidity, wind speed, and globe temperature. These equipments were distributed along three different streets where a single species is planted. Sibipiruna, Ipê-de-El-Salvador and Tipuana were the chosen species of trees commonly used in the streets of Piracicaba. Thermal images of the measuring points and questionnaires aimed at the local people will be used to help interpreter different arrangements. All this data was applied for calculate the Universal Thermal Comfort Index (UTCI). The presence of trees influenced the climatic variables. The three areas showed significant differences between streets with and without trees, both in the dry and rainy period. The streets with trees presented lower temperature, higher humidity and lower wind speed (except in Area 3). In all cases, the trees species had positive effects on human thermal comfort index.The results can help to take choices based on the role that trees should play in a city, such as improve thermal comfort for the population.As contínuas transformações nas áreas urbanas têm trazido muitos problemas relacionados à perda da qualidade ambiental, como por exemplo, a falta de árvores nas ruas. Podemos dizer que a arborização urbana influencia diretamente no conforto térmico das cidades, e as pessoas podem realmente sentir na pele a diferença nas condições ambientais entre uma rua arborizada e outra sem árvores. Por isso, um melhor manejo destas árvores pode beneficiar a qualidade do ambiente local, e consequentemente, a qualidade de vida da população. Um dos primeiros passos nesse manejo é a escolha de espécies, porém poucos estudos abordam o real efeito desta escolha para as condições ambientais futuras do local. O presente trabalho tem como objetivo investigar o efeito do uso de diferentes espécies na arborização urbana para o conforto térmico na cidade de Piracicaba-SP. Para isso, foi medida a temperatura do ar, umidade relativa, velocidade do vento, e temperatura de globo. Os equipamentos foram distribuídos ao longo de três ruas diferentes onde uma das espécies escolhida prevalecia. Sibipiruna, Ipê-de-El-Salvador e Tipuana foram as espécies escolhidas dentre as árvores mais utilizadas nas ruas de Piracicaba. Imagens termais dos pontos de medição e questionários voltados à população local foram utilizados para auxiliar na interpretação. Todos os dados coletados foram aplicados no cálculo do Índice de Conforto Térmico Universal (UTCI). A presença de árvores influenciou diretamente nas variáveis climáticas estudadas. As três áreas apresentaram diferença significativa entre os pontos arborizados e não arborizados, tanto no período seco quanto no chuvoso. As ruas arborizadas apresentaram menor temperatura, maior umidade relativa e menor velocidade do vento (exceto na área 3). Os resultados podem ajudar na tomada de decisões baseando-se no papel das árvores dentro do ambiente urbano, como a melhoria do conforto térmico para a população.
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Leonard, Norman. "The effects of the invasive exotic Chinese tallow tree (Triadica sebifera) on amphibians and aquatic invertebrates". ScholarWorks@UNO, 2008. http://scholarworks.uno.edu/td/656.
Abstract (sommario):
This dissertation addresses the question of how leaf litter from trees affects animals that live in aquatic environments, with an emphasis on the effect of Chinese tallow (Triadica sebifera) leaf litter on anuran larvae (i.e., frog tadpoles). This question is important to our understanding of how allochthonous inputs to aquatic habitats drive biodiversity in wetlands. It also addresses a timely conservation concern in southeastern Louisiana where invasion by Chinese tallow trees (Triadica sebifera) is displacing native trees. The invasion process is homogenizing forest composition and changing the quantity and quality of litter inputs to ponds from those produced by a mixture of native species to that of a single invasive species. This change in litter quality may have important effects on aquatic animals because leaf litter that falls into ponds is an important source of nutrients and energy in wetland foodwebs. Leaf litter also affects water quality via effects on dissolved oxygen and leaching of defensive compounds, which may subsequently affect the diversity and performance of aquatic animals. Herein I address these issues by presenting a series of studies in which tadpole and aquatic invertebrate responses were tested using leaf litter from Chinese tallow leaves and three native tree species. The major findings of this research are: (1) Leaf litter has a direct effect on water quality (2) Chinese tallow can cause differential survival and performance of tadpoles (3) Differences in water quality due to leaf litter can cause changes in tadpole behavior (4) Chinese tallow leaf litter breaks down much faster than litter from native trees (5) Difference in litter breakdown rates influence aquatic community composition.
28
Panter, Jonathan Paul. "Effects of drought and vegetation management on the establishment of 3 tree species in Northamptonshire, England". Thesis, Cranfield University, 2006. http://dspace.lib.cranfield.ac.uk/handle/1826/8541.
Abstract (sommario):
Water is a limiting factor in the distribution and growth of trees. Changing climatic
conditions are likely to significantly effect tree species development. The planting and
establishment of trees needs to take into account these changing factors in terms of
design and species selection. This study looked at survival and growth of newly planted
trees under field scale conditions and the effects of soil water availability and ground
treatments. The experiment followed a blocked plan allowing a line source design to
irrigate three tree species, ash, Douglas fir and oak. Each plot of 90 trees was divided
into 5 irrigation subplots with varying levels of water application. Two ground
treatments, bare ground and vegetated were also applied. Over a three year period,
there was a significant effect of species (P<0.001) and herbicide application (P<0.01)
on tree survival. Tree height and diameter were significant (P<0.01) between species
and herbicide. Irrigation had a significant effect on growth rates of all species with no
effect on survival. Ground vegetation biomass significantly increased in high irrigation
subplots (P<0.01), with increasing festuca rubra dominance decreasing plant diversity
(R2=0.8533). The results suggest that soil moisture availability increases tree growth
but does not significantly improve survival rates of the tree species studied. Water is a
key factor in the establishment of trees with maintained soil moisture increasing growth
development of individuals. Therefore site and species selection are essential in the
design of woodland plantings for conservation, recreation and commercial activities.
29
Lübbe, Torben Verfasser], Christoph [Akademischer Betreuer] [Gutachter] Leuschner e Dirk [Gutachter] [Hölscher. "Effects of tree species diversity and soil drought on productivity, water consumption and hydraulic functioning of five temperate broad-leaved tree species / Torben Lübbe. Betreuer: Christoph Leuschner. Gutachter: Christoph Leuschner ; Dirk Hölscher". Göttingen : Niedersächsische Staats- und Universitätsbibliothek Göttingen, 2016. http://d-nb.info/1105760073/34.
30
Iacopino, Simone. "Exploring the multiple effects of the invasive alien black locust tree". Doctoral thesis, Università degli studi di Padova, 2019. http://hdl.handle.net/11577/3425418.
Abstract (sommario):
Black locust (Robinia pseudoacacia L.) is one of the most widespread invasive alien tree species in Europe and throughout the world. Its spread has been favoured by its ecological attitudes and economic relevance, with positive and negative implications. The aim of this thesis was to further develop knowledge on the black locust’s ecological and socio-economic drivers. A stand, landscape and national scale were considered. At the stand scale, ecological impacts on the plant community were assessed through a comparative approach, based on a sample of pairs of woodlands, invaded or non-invaded by black locust. A focus on a sample of three types of landscape (rural, riverine and urban) allowed black locust impacts to be compared across different environmental contexts. A second focus on a sample of three European cities (Berlin, Padova and Roma) allowed the impacts of both black locust dominance and urban matrix properties to be investigated across urban environments at different latitudes. Socio-economic drivers were investigated at a national scale in Italy, linking these factors with changes in both land cover and black locust distribution. Knowledge on the drivers of black locust spread and its effects on natural resources is deepened, offering insights into a desirable trade-off between biodiversity conservation and black locust socio-economic significance at multiple scales and contexts.La robinia (Robinia pseudoacacia L.) è una delle specie arboree aliene invasive più diffuse in Europa e nel mondo. La diffusione di questa specie è stata favorita dalla sua amplitudine ecologica e dai suoi diversificati interessi economici, determinandone conseguenze positive e negative. Lo scopo della tesi è di approfondire le conoscenze sui fattori ecologici ed economici che hanno causato e caratterizzano la sua distribuzione. Sono state prese in considerazione diverse scale di studio, una scala di popolamento, una di paesaggio e una nazionale. A scala di popolamento, sono stati valutati gli impatti ecologici sulla comunità vegetale seguendo un metodo comparativo, basato su un campione di coppie di boschi, invasi o meno dalla robinia. È stato condotto un confronto degli impatti di robinia in diversi contesti ambientali mediante un approfondimento su un campione di tre tipi di paesaggio (rurale, fluviale e urbano). Un secondo approfondimento su un campione di tre città europee (Berlino, Padova e Roma) ha permesso invece di indagare gli impatti della copertura di robinia e delle proprietà della matrice urbana in contesti urbani a latitudini molto diverse. I fattori socio-economici sono stati indagati al livello nazionale italiano, collegandoli con i cambiamenti della copertura del suolo e della distribuzione della robinia. Le conoscenze sulle cause della diffusione della robinia e dei suoi effetti sulle risorse naturali vengono approfondite offrendo spunti di riflessione su un auspicabile bilanciamento tra conservazione della biodiversità e valorizzazione socio-economica di questa specie, a molteplici scale e contesti.
31
Myers, Teri S. "Effects of nitrogen and water on growth, photosynthesis, and leaf properties of deciduous tree species with consequences for gypsy moth herbivory". Morgantown, W. Va. : [West Virginia University Libraries], 2000. http://etd.wvu.edu/templates/showETD.cfm?recnum=1536.
Abstract (sommario):
Thesis (Ph. D.)--West Virginia University, 2000.Title from document title page. Document formatted into pages; contains ix, 118 p. : ill. (some col.). Vita. Includes abstract. Includes bibliographical references.
32
Yee, Donald A. Juliano Steven A. "Effects of species interactions and productivity on aquatic macroinvertebrate diversity and community composition in tree holes patterns and mechanisms /". Normal, Ill. : Illinois State University, 2006. http://proquest.umi.com/pqdweb?index=0&did=1251832821&SrchMode=1&sid=5&Fmt=2&VInst=PROD&VType=PQD&RQT=309&VName=PQD&TS=1179157986&clientId=43838.
Abstract (sommario):
Thesis (Ph. D.)--Illinois State University, 2006.Title from title page screen, viewed on May 14, 2007. Dissertation Committee: Steven A. Juliano (chair), Roger C. Anderson, L. Philip Lounibos, Wade A. Nichols, William L. Perry. Includes bibliographical references (leaves 145-162) and abstract. Also available in print.
33
Martin-Benito, Dario, Kevin Anchukaitis, Michael Evans, Río Miren del, Hans Beeckman e Isabel Cañellas. "Effects of Drought on Xylem Anatomy and Water-Use Efficiency of Two Co-Occurring Pine Species". MDPI AG, 2017. http://hdl.handle.net/10150/625999.
Abstract (sommario):
Exploring how drought influences growth, performance, and survival in different species is crucial to understanding the impacts of climate change on forest ecosystems. Here, we investigate the responses of two co-occurring pines (Pinus nigra and Pinus sylvestris) to interannual drought in east-central Spain by dendrochronological and wood anatomical features integrated with isotopic ratios of carbon (delta C-13) and oxygen (delta O-18) in tree rings. Our results showed that drought induces both species to allocate less carbon to build tracheid cell-walls but increases tracheid lumen diameters, particularly in the transition wood between early and latewood, potentially maximizing hydraulic conductivity but reducing resistance to embolism at a critical phase during the growing season. The thicker cell-wall-to-lumen ratio in P. nigra could imply that its xylem may be more resistant to bending stress and drought-induced cavitation than P. sylvestris. In contrast, the higher intrinsic water-use efficiency (iWUE) in P. sylvestris suggests that it relies more on a water-saving strategy. Our results suggest that narrower cell-walls and reduced growth under drought are not necessarily linked to increased iWUE. At our site P. nigra showed a higher growth plasticity, grew faster and was more competitive than P. sylvestris. In the long term, these sustained differences in iWUE and anatomical characters could affect forest species performance and composition, particularly under increased drought stress.
34
Hantsch, Lydia [Verfasser], Helge [Akademischer Betreuer] Bruelheide, Uwe [Akademischer Betreuer] Braun e Christopher C. [Akademischer Betreuer] Mundt. "Tree diversity effects on species richness and infestation of foliar fungal pathogens in European tree diversity experiments / Lydia Hantsch. Betreuer: Helge Bruelheide ; Uwe Braun ; Christopher C. Mundt". Halle, Saale : Universitäts- und Landesbibliothek Sachsen-Anhalt, 2013. http://d-nb.info/1046563483/34.
35
Karlsson, Matts. "Natural regeneration of broadleaved tree species in southern Sweden : effects of silvicultural treatments and seed dispersal from surronding stands /". Alnarp : Swedish Univ. of Agricultural Sciences (Sveriges lantbruksuniv.), 2001. http://epsilon.slu.se/avh/2001/91-576-6080-8.pdf.
36
Dordel, Julia. "Effects of nurse tree species on growth environment and physiology of underplanted Toona ciliata Roemer in subtropical Argentinean plantations". Thesis, University of British Columbia, 2009. http://hdl.handle.net/2429/11174.
Abstract (sommario):
Toona ciliata Roem. plantations require a nurse-tree overstorey to minimize damage from drought and frost in north-eastern Argentina. Nurse-species vary in their facilitative and competitive abilities, thus influencing trade-offs among T. ciliata establishment success, stem quality and productivity, and ultimately stand revenues. The first objective was to quantify the influence of nurse species (G. robusta A. Cunn., Pinus elliottii Englm. x Pinus caribaea Morelet, P. taeda L.) and thinning density on mortality, stem morphology and growth of under-planted T. ciliata. Trade-offs among performance traits were considered in developing recommendations for nurse species selection and density management. The second objective was to examine interspecific interaction mechanisms by determining the effects of nurse species and thinning intensities on light, soil water and nutrient availability to T. ciliata. The final objective was to link T. ciliata establishment success and early growth to soil water availability, by calibrating the two-dimensional forest hydrology model, ForWaDy. To develop a stand management tool for guiding establishment of T. ciliata plantations it was found that T. ciliata responded more to nurse species identity than density. G. robusta was less competitive with T. ciliata for soil nutrients and soil water than either of the pine species: P. elliottii x P. caribaea was an strong competitor for water while P. taeda was a strong competitor for nutrients. G. robusta, by contrast, increased water and phosphorus availability to T. ciliata. Density effects varied with nurse species and performance traits. ForWaDy had good predictive capability for early T. ciliata performance, and was especially discriminatory among nurse species effects. This study shows that nurse species and thinning effects depend on management objectives, but that nurse species choice can be more important than thinning for increasing early T. ciliata performance. Future research employing a greater range of overstorey species, thinning densities, tree ages and environmental conditions will improve predictions of mixed stand productivity under a broader range of conditions. The study contributes to a better understanding of competitive and facilitative interactions in nurse tree plantations and emphasize the need for long-term empirical and modeling studies of mixed species stand dynamics.
37
Contreras, Ruiz Esparza Ana Beatriz. "Effects of fire and selective logging on understory birds and tree species in a tropical montane forest, MeÌxico". Thesis, University of East Anglia, 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.443181.
38
Karlsson, Matts. "Natural regeneration of broadleaved tree species in southern Sweden : effects of silvicultural treatments and seed dispersal from surrounding stands /". Alnarp : Swedish University of Agricultural Sciences, 2001. http://diss-epsilon.slu.se/archive/00000042/.
Abstract (sommario):
Thesis (doctoral)--Swedish University of Agricultural Sciences, 2001.Appendix reprints five papers and manuscripts, four co-authored with others. Includes bibliographical references. Also partially issued electronically via World Wide Web in PDF format; online version lacks appendix.
39
Rahman, Mohammad. "Effects of species and rooting conditions on the growth and cooling performance of urban trees". Thesis, University of Manchester, 2013. https://www.research.manchester.ac.uk/portal/en/theses/effects-of-species-and-rooting-conditions-on-the-growth-and-cooling-performance-of-urban-trees(1211fb4b-2eb9-4ddc-99e1-c1ee37fccc03).html.
Abstract (sommario):
The urban heat island (UHI) is a problem that is likely to be exacerbated by ongoing climate change, but it is often claimed that urban trees can mitigate it and hence adapt our cities to climate change. Many researchers have attempted to quantify the cooling effects of trees using modelling approaches. However, the major disadvantage of most of the models is that they consider all vegetation to act as a single saturated layer and that their effect is merely proportional to its surface cover. Therefore, they fail to take into account potential differences between tree species and the effect of different environmental and growing conditions. To address this issue four different studies were conducted in Manchester, UK from February, 2010 to December, 2012. The studies compared the growth and cooling abilities of several commonly planted urban tree species, and investigated a single species planted in a range of growing conditions: investigating the effect of urban soil compaction and aeration and also the effect of urbanization and simulated climate change in the rooting zone. Overall, our studies showed that species selection and growing conditions can substantially alter the evapotranspirational cooling provided by urban trees. Fast growing species such as Pyrus calleryana, with their dense and wide canopy can provide cooling up to 2.2 kW tree-1, 3-4 times that of Sorbus arnoldiana, which have a thinner and narrower canopy and a moderate growth rate. P. calleryana was also investigated under three contrasting growth conditions: in cut-out pits in pavements; in grass verges; and in pits filled with Amsterdam soil. Trees in the less compacted Amsterdam soil had grown almost twice as fast as those in pavements and also had better leaf physiological performance. Together with a longer growing season, and better uptake of soil nutrients and moisture, trees grown in Amsterdam soil provided evapotranspirational cooling of up to 7kW, 5 times higher than those grown in pavements. Another experiment in which P. calleryana trees were planted in 3 standard planting techniques with non-compacted load bearing soils and with or without permeable slabs showed that optimum cooling is not only dependent on preventing soil compaction but also on ensuring that the covering materials are permeable to oxygen. Trees in the open pits provided up-to 1 kW of cooling, compared to around 350 and 650 W by the small and large covered pits respectively. Our final experiment showed that urbanization can increase tree growth by 20-30%; however, despite being under more water stressed conditions trees grown in simulated climate change plots had 40% higher sap flux density, and hence cooling potential. The study suggested that at least with P. calleryana, transpirational cooling benefit might be enhanced in places like Manchester with increased soil temperature in future, but potentially at the expense of photosynthesis and carbon gain. Together these studies show that evaporative cooling of trees depends strongly on both species and growing conditions. If incorporated into regional and local energy exchange models our results can help us to quantify the magnitude and effectiveness of greenspaces in the city in adapting them to climate change.
40
Bantle, Andreas Karl [Verfasser], e Egbert [Akademischer Betreuer] Matzner. "Tree species effects on the release of dissolved organic carbon and nitrogen from decomposing logs / Andreas Karl Bantle. Betreuer: Egbert Matzner". Bayreuth : Universität Bayreuth, 2015. http://d-nb.info/1075807859/34.
41
Kirby, Kathryn. "Land-use change in the Neotropics : regional-scale predictors of deforestation and local effects on carbon storage and tree-species diversity". Thesis, McGill University, 2004. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=82264.
Abstract (sommario):
Land-use change, and in particular tropical deforestation, is the leading cause of species extinctions globally, and is the second most important source of CO2 emissions after fossil fuel combustion. I examine two policy-relevant questions that relate to tropical deforestation and land use change: (1) At regional scales, what biophysical and infrastructure-related factors are associated with deforestation? and (2) At a local scale, what are some of the impacts of land use change on above- and below-ground carbon stocks and on tree-species richness? The first question was examined for the Brazilian Amazon through spatially-explicit correlation analyses of deforestation and a series of predictor variables that included highways and roads, annual rainfall, dry season length, soil characteristics, site accessibility, and population density. The proximity of a site to roads and highways was the strongest predictor of deforestation, with more accessible sites more likely to be deforested. Dry season length was also a strong, positive predictor of deforestation. The results suggest that current plans to expand road infrastructure in Amazonia will have a significant impact on the forests of the areas transected.The second question was examined in the context of a 3,198 ha area in Eastern Panama that is managed collectively by an Indigenous Embera community.
42
Jessen, Maria-Theresa. "Effects of climate warming on the performance of three boreal tree seedling species in interaction with moss cover and fire history". Thesis, Umeå universitet, Institutionen för ekologi, miljö och geovetenskap, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-136177.
Abstract (sommario):
Forest regeneration in the form of successful seedling establishment is a key factor for the persistence of a healthy forest ecosystem. Tree seedlings grow in a complex environment shaped by over- and understory and competition for light, nutrients and water. Not much research has been done on how climate change is impacting on seedling performance through direct and indirect warming effects including possible interactions with the growth environment i.e. understory vegetation. To elucidate these, seedlings of B. pubescens, P. sylvestris and P. abies were planted into a full-factorial experiment consisting of randomly assigned plant functional group (moss) removal in combination with passive warming (open-top chambers [OTCs]) along a post-fire chronosequence. Each seedling’s survival and growth had been surveyed over a period of three years (not as part of this thesis). At the end of the experiment, growth assessment in terms of biomass determination was done, by harvesting selected individuals. Growth has been found to be species-specific but without evidence of a direct or interactive warming effect. The survival analysis highlights that mosses promoted a positive warming effect on survival in the young and intermediate successional stages regardless of seedling species. In the old successional stage warming reduced survival regardless of moss presence explicitly for B. pubescens and P. sylvestris. If, as anticipated, climate change induces a shift toward younger forest stands by altering the fire frequency and climate warms, moss cover can therefore become a critical factor for seedling survival in the boreal forest.
43
Zatout, Masoud Moustafa Mohamed. "The roles of exotic and native tree species in preventing desertification and enhancing degraded land restoration in the north east of Libya : reciprocal effects of environmental factors and plantation forestry on each other, assessed by observations on growth and reproductive success of relevant tree species, and environmental factors analysed using multivariate statistics". Thesis, University of Bradford, 2011. http://hdl.handle.net/10454/5708.
Abstract (sommario):
Today's arid and semi-arid zones of the Mediterranean are affected by desertification, resulting from various factors, including climatic variations and human activities such as overcultivation, overgrazing and deforestation. Afforestation programs are one of the most effective means in preventing desertification. For many years Libya has had afforestation programs in order to restore degraded land and in response to rapid desert encroachment in the north east of Libya, in the area called the Jabal Akhdar (Green Mountain), which has been investigated in this study. The purpose of this research was to investigate the relative roles of exotic compared to native tree species in preventing desertification and enhancing degraded land restoration in the Jabal Akhdar. The effect of environmental factors on exotic compared to native tree species have been assessed by observations on growth and reproductive success of the species, including variables of stocking rate, trunk diameter, tree height, crown diameter, tree coverage, natural mortality, felling and seedling regeneration, as well as calculated variables, derived from these measurements. The effects of methods and age of afforestation on the promotion of biological diversity have been investigated using the Shannon-Wiener diversity index. The effects of tree species on soil depth have also been investigated. Multivariate statistical analyses of site, species and environmental data, using both cluster analyses and factor analyses have been performed, with the aim of determining what is influencing the species, crops or differentiating between the sites, based on soil depth, angle of slope, altitude, rainfall and air temperature values. Pinus halepensis showed success in its growth and regeneration, particularly at higher altitudes and steeper slopes. Cupressus sempervirens was successful in growth and regeneration in the mountains. The exotic Eucalyptus gomphocephala was very successful in its growth, but did not regenerate well, while the exotic Acacia cyanophylla trees had a failure of both growth and regeneration. E. gomphocephala species appeared to favour relativley the flatter (non-mountain) sites, while A. Cyanophylla appeared to favour relativly the mountain sites. All the species responded positively to greater rainfall and deep soil, but they differed in where they were most likely to be successful. Environmental factors such as climate, terrain and soil are the main determinants of species distribution in the study area, in addition to their impact on the growth of the main trees. There appeared not to be any relationship between biodiversity and whether the main trees were native or exotic, and only P. halepensis showed any negative effect on the abundance of shrubs. There was greater diversity of trees and shrubs generally at the younger sites than the old sites. The present study emphasises the current mismanagement of planted forests, particularly with overgrazing contributing to desertification, through preventing tree growth and eliminating most sapling regeneration. This study concludes by making recommendations for more effective choice of tree species to plant, and for subsequent management to improve afforestation programmes in the Jabal Akhdar area.
44
Ei, Thandar Bol. "Effects of forest disturbances on edaphic factors and tree community structure of tropical evergreen forest; a case study in Kyaik Htee Yoo Nature Reserve Forest, Mon State, Myanmar". Kyoto University, 2017. http://hdl.handle.net/2433/228246.
45
Krueger, Kirk L. "Effects of Sampling Sufficiency and Model Selection on Predicting the Occurrence of Stream Fish Species at Large Spatial Extents". Diss., Virginia Tech, 2009. http://hdl.handle.net/10919/26214.
Abstract (sommario):
Knowledge of species occurrence is a prerequisite for efficient and effective conservation and management. Unfortunately, knowledge of species occurrence is usually insufficient, so models that use environmental predictors and species occurrence records are used to predict species occurrence. Predicting the occurrence of stream fishes is often difficult because sampling data insufficiently describe species occurrence and important environmental conditions and predictive models insufficiently describe relations between species and environmental conditions. This dissertation 1) examines the sufficiency of fish species occurrence records at four spatial extents in Virginia, 2) compares modeling methods for predicting stream fish occurrence, and 3) assesses relations between species traits and model prediction characteristics.
The sufficiency of sampling is infrequently addressed at the large spatial extents at which many management and conservation actions take place. In the first chapter of this dissertation I examine factors that determine the sufficiency of sampling to describe stream fish species richness at four spatial extents across Virginia using sampling simulations. Few regions of Virginia are sufficiently sampled, portending difficulty in accurately predicting fish species occurrence in most regions. The sufficient number of samples is often large and varies among regions and spatial scales, but it can be substantially reduced by reducing errors of sampling omission and increasing the spatial coverage of samples.
Many methods are used to predict species occurrence. In the second chapter of this dissertation I compare the accuracy of the predictions of occurrence of seven species in each of three regions using linear discriminant function, generalized linear, classification tree, and artificial neural network statistical models. I also assess the efficacy of stream classification methods for predicting species occurrence. No modeling method proved distinctly superior. Species occurrence data and predictor data quality and quantity limited the success of predictions of stream fish occurrence for all methods. How predictive models are built and applied may be more important than the statistical method used.
The accuracy, generality (transferability), and resolution of predictions of species occurrence vary among species. The ability to anticipate and understand variation in prediction characteristics among species can facilitate the proper application of predictions of species occurrence. In the third chapter of this dissertation I describe some conservation implications of relations between predicted occurrence characteristics and species traits for fishes in the upper Tennessee River drainage. Usually weak relations and variation in the strength and direction of relations among families precludes the accurate prediction of predicted occurrence characteristics. Most predictions of species occurrence have insufficient accuracy and resolution to guide conservation decisions at fine spatial grains. Comparison of my results with alternative model predictions and the results of many models described in peer-reviewed journals suggests that this is a common problem. Predictions of species occurrence should be rigorously assessed and cautiously applied to conservation problems. Collectively, the three chapters of this dissertation demonstrate some important limitations of models that are used to predict species occurrence. Model predictions of species occurrence are often used in lieu of sufficient species occurrence data. However, regardless of the method used to predict species occurrence most predictions have relatively low accuracy, generality and resolution. Model predictions of species occurrence can facilitate management and conservation, but they should be rigorously assessed and applied cautiously.Ph. D.
46
Tanjung, Rosye Hefmi Rechnelty. "Effects of glyphosate on seedlings of conifer and broadleaf tree species native to British Columbia, with particular regard to root-fungus interaction". Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2001. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp04/NQ61687.pdf.
47
Li, Ying [Verfasser], e Goddert [Akademischer Betreuer] Oheimb. "Effects of biodiversity and abiotic environment on the growth rates of native tree species in subtropical plantations / Ying Li ; Betreuer: Goddert Oheimb". Lüneburg : Universitätsbibliothek der Leuphana Universität Lüneburg, 2017. http://d-nb.info/1125105364/34.
48
Jacob, Andreas Verfasser], Christoph [Akademischer Betreuer] Leuschner e Dirk [Akademischer Betreuer] [Hölscher. "Effects of tree species composition on fine root biomass and dynamics in the rhizosphere of deciduous tree stands in the Hainich National Park (Thuringia) / Andreas Jacob. Gutachter: Christoph Leuschner ; Dirk Hölscher. Betreuer: Christoph Leuschner". Göttingen : Niedersächsische Staats- und Universitätsbibliothek Göttingen, 2013. http://d-nb.info/1044871601/34.
49
Langenbruch, Christina. "Effects of nutrient cycling through litter of different broadleaved deciduous tree species on soil biochemical properties and the dynamics of carbon and nitrogen in soil". Doctoral thesis, Niedersächsische Staats- und Universitätsbibliothek Göttingen, 2012. http://hdl.handle.net/11858/00-1735-0000-000D-F1C2-F.
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Jones, Kevin Christopher. "Ecological effects of the feeding and construction activities of the Eurasian beaver (Castor fiber) in Scotland : implications for reintroduction". Thesis, University of Stirling, 2006. http://hdl.handle.net/1893/211.
Abstract (sommario):
Beavers have been described as a “keystone species” and “ecosystem engineers”, and in this dual role have great potential to physically modify their environment through tree-felling, foraging and construction activities. The resultant change in habitat heterogeneity can affect the flora and fauna that share the habitat with them. There has been recent interest in reintroducing the Eurasian beaver to the United Kingdom after an absence of over 400 years. To date, no research (aside from this thesis) has focussed on beaver ecology and behaviour in Scotland. This study has investigated the ecological effects of a small number of beavers in two enclosed but semi-natural Scottish sites at Bamff in Perthshire. The research conducted over a three-year period, with particular emphasis on the effects of tree-felling, foraging and construction activities. Trees were felled for both dietary and construction purposes, with felling rates being influenced by habitat availability, quality and the degree of habitat modification required. Highest rates were evident during the initial colonisation period of marginal sites (c. >300 trees / beaver / calendar year), and lowest rates in later years of occupation of more optimal sites (c. 55 – 70 trees / beaver / calendar year). Preferences were generally for willow and aspen trees, with conifers almost entirely avoided, and smaller trees preferred over larger ones. Proximity of trees to waterbodies was also an important factor, with nearer trees favoured, and generally most felling occurred within 50 m of water. Such behaviour followed the principles of optimal central place foraging. These preferences were less predictable however when intense construction activity was undertaken, with larger trees preferred and generic preferences for deciduous trees apparently invalid. In such cases, close proximity to the construction site was of prime importance. Increased cover of herbaceous plant species was observed in beaver-created canopy gaps in riparian woodland, whilst macrophyte diversity within waterbodies increased slightly in areas of herbaceous grazing. The diversity of terrestrial ground invertebrates was highest in areas of heavy tree-felling, and invertebrate richness and abundance was greatest in areas of herbaceous grazing under an intact tree-canopy. Furthermore, the abundance, diversity and richness of macroinvertebrate communities were increased by beaver-generated woody debris in ponds and streams. Overall, 30% of all macroinvertebrate species collected were found only in beaver-affected areas, due to the refugia and food supply provided by beaver dams, caches and lodges, as well as hydrological effects of these structures. These results are discussed with reference to future plans to return the beaver to Scotland. The habitat usage and modification of riparian ecosystems in northern Britain is likely to be similar to that found in this study, and the results are believed to be relevant, applicable and transferable to many areas of Scotland.