bluuebunny/crossref_metadata_2025_split huggingface dataset:
Predicting tree death for Fagus sylvatica and Abies alba using permanent plot data
Authors: Wunder Jan , Reineking Björn , Matter Jean‐François , Bigler Christof , Bugmann Harald 
Published: February 2009

AbstractQuestion:How well can mortality probabilities of deciduous trees(Fagus sylvatica)and conifers(Abies alba)be predicted using permanent plot data that describe growth patterns, tree species, tree size and site conditions?Location:Fagusforests in the montane belt of the Jura folds (Switzerland).Method:Permanent plot data were used to develop and validate logistic regression models predicting survival probabilities of individual trees. Backward model selection led to a reduced model containing the growth‐related variable ‘relative basal area increment’ (growth‐dependent mortality) and variables not directly reflecting growth such as species, size and site (growth‐independent mortality).Results:The growth‐mortality relationship was the same for both species (growth‐dependent mortality). However, species, site and tree size also influenced mortality probabilities (growth‐independent mortality). The predicted survival probabilities of the final model were well calibrated, and the model showed an excellent discriminatory power (area under the receiver operating characteristic curve = 0.896).Conclusion:Mortality probabilities ofFagus sylvaticaandAbies albacan be predicted with high discriminatory power using a well calibrated logistic regression model. Extending this case study to a larger number of tree species and sites could provide species‐ and site‐specific tree mortality models that allow for more realistic projections of forest succession.
The RAINFOR database: monitoring forest biomass and dynamics
Authors: Peacock J. , Baker T.R. , Lewis S.L. , Lopez‐Gonzalez G. , Phillips O.L. 
Published: February 2009

AbstractProblem: Data from over 100 permanent sample plots which have been studied for 10–20 years need a suitable system for storage which allows simple data manipulation and retrieval for analysis.Methods: A relational database linking tree records, taxonomic nomenclature and corresponding environmental data has been built in MS Access as part of the RAINFOR project.Conclusion: The database allows flexible and long‐term use of a large amount of data: more than 100 tree plots across Amazonia, incorporating over 80 000 records of individual trees and over 300 000 total records of tree diameter measurements from successive censuses. The database is designed to enable linkages to existing soil, floristic or plant‐trait databases. This database will be a useful tool for exploring the impact of environmental factors on forest structure and dynamics at local to continental scales, and long term changes in forest ecology. As an early example of its potential, we explore the impact of different methodological assumptions on estimates of tropical forest biomass and carbon storage.
Leaf green‐up in a semi‐arid African savanna ‐separating tree and grass responses to environmental cues
Authors: Archibald S. , Scholes R.J. 
Published: February 2009

AbstractQuestion: Can satellite time series be used to identify tree and grass green‐up dates in a semi‐arid savanna system, and are there predictable environmental cues for green‐up for each life form?Location: Acacia nigrescens /Combretum apiculatum savanna, Kruger National Park, South Africa (25° S, 31° E).Methods: Remotely‐sensed data from the MODIS sensor were used to provide a five year record of greenness (NDVI) between 2000 and 2005. The seasonal and inter‐annual patterns of leaf display of trees and grasses were described, using additional ecological information to separate the greening signal of each life form from the satellite time series. Linking this data to daily meteorological and soil moisture data allowed the cues responsible for leaf flush in trees and grasses to be identified and a predictive model of savanna leaf‐out was developed. This was tested on a 22‐year NDVI dataset from the Advanced Very High Resolution Radiometer.A day length cue for tree green‐up predicted 86% of the green‐ups with an accuracy better than one month. A soil moisture and day length cue for grass green‐up predicted 73% of the green‐ups with an accuracy better than a month, and 82% within 45 days. This accuracy could be improved if the temporal resolution of the satellite data was shortened from the current two weeks.Conclusions: The data show that at a landscape scale savanna trees have a less variable phenological cycle (within and between years) than grasses. Realistic biophysical models of savanna systems need to take this into account. Using climatic data to predict these dynamics is a feasible approach.
Vegetation shifts towards wetter site conditions on oceanic ombrotrophic bogs in southwestern Sweden
Authors: Gunnarsson Urban , Flodin Lars‐Åke 
Published: February 2009

AbstractQuestion: Is ombrotrophic bog vegetation in an oceanic region of southwestern Sweden changing in the same direction over a five year period (1999 ‐ 2004) as northwest European bogs in the last 50 years, i.e. towards drier and more eutrophic vegetation?Location: The province of Halland, southwestern Sweden.Methods: Changes in species composition were monitored in 750 permanently marked plots in 25 ombrotrophic bogs from 1999 to 2004. Changes in species occurrences and richness were analysed and a multivariate statistical method (DCA) was used to analyse vegetation changes.Results: The species composition changed towards wetter rather than drier conditions, which is unlike the general pattern of vegetation change on bogs in northwestern Europe. Species typical of wetter site conditions including most Sphagnum species increased in abundance on the bogs until 2004. The total number of species per plot increased, mostly due to the increased species richness of Sphagnum species. Nitrogen‐demanding (eutrophic) species increased in occurrence.Conclusions: Ombrotrophic bog vegetation in an oceanic region in Sweden became wetter and was resilient to short‐term climatic shifts, after three years of below normal precipitation followed by several years with normal precipitation levels. Shifts towards more nitrogen demanding species were rapid in this region where the deposition levels have been high for several decades.
Bayesian classification of vegetation types with Gaussian mixture density fitting to indicator values
Authors: Witte Jan‐Philip M. , Wójcik Rafał B. , Torfs Paul J.J.F. , de Haan Martin W.H. , Hennekens Stephan 
Published: February 2009

AbstractQuestion:Is it possible to mathematically classify relevés into vegetation types on the basis of their average indicator values, including the uncertainty of the classification?Location:The Netherlands.Method:A large relevé database was used to develop a method for predicting vegetation types based on indicator values. First, each relevé was classified into a phytosociological association on the basis of its species composition. Additionally, mean indicator values for moisture, nutrients and acidity were computed for each relevé. Thus, the position of each classified relevé was obtained in a three‐dimensional space of indicator values. Fitting the data to so called Gaussian Mixture Models yielded densities of associations as a function of indicator values. Finally, these density functions were used to predict the Bayesian occurrence probabilities of associations for known indicator values. Validation of predictions was performed by using a randomly chosen half of the database for the calibration of densities and the other half for the validation of predicted associations.Results and Conclusions:With indicator values, most reléves were classified correctly into vegetation types at the association level. This was shown using confusion matrices that relate (1) the number of relevés classified into associations based on species composition to (2) those based on indicator values. Misclassified relevés belonged to ecologically similar associations. The method seems very suitable for predictive vegetation models.
Use of vegetation classification and plant indicators to assess grazing abandonment in Estonian coastal wetlands
Authors: Burnside Niall G. , Joyce Chris B. , Puurmann Elle , Scott Dawn M. 
Published: February 2009

AbstractQuestion: What are the effects of grazing abandonment on the vegetation composition of Estonian coastal wetlands?Location: Vormsi Island and Silma Nature Reserve in western Estonia, Europe.Methods: Local knowledge and field reconnaissance were used to identify current and historical management levels of wetland sites within the west Estonian study area. Nine study sites, with varying management histories, were selected comprising an area of 287 ha. A total of 198 quadrats were taken from 43 distinct vegetation patches in five of the sites. TWINSPAN analysis was used to identify community type, and a phytosociological key was constructed for character taxa. This vegetation classification was then applied within a GIS‐based context to classify all the study sites, using a ground survey technique and 1:2000 scale air photos.Results: We identified 11 different brackish coastal wetland community types. Indicator species were defined with community characteristics for the seven main vegetation types readily recognisable in the field. Coastal wet grasslands were most extensive in grazed sites, or sites that had been more intensively grazed, while abandoned sites were largely composed of Phragmites australis stands, tall grassland, and scrub. Site variations based on vegetation composition were significantly correlated with past grazing intensity. Plant community types showed significant edaphic differences, with particularly low soil moisture and high conductivity and pH for open pioneer patches compared to other vegetation types.Conclusion: Abandonment of traditionally grazed coastal grasslands threatens their characteristic biodiversity. This study found that grazing abandonment reduced the extent of coastal wetland grasslands of particular conservation value. Nevertheless, plant species of conservation interest were found across the sequence of community types described. The study shows that grazing is an important factor influencing coastal wetland plant communities but suggests that vegetation distribution is affected by environmental variables, such as topography.
Habitat engineering under dry conditions: The impact of pikas (Ochotona pallasi) on vegetation and site conditions in southern Mongolian steppes
Authors: Wesche Karsten , Nadrowski Karin , Retzer Vroni 
Published: February 2009

AbstractQuestion:Does ecosystem engineering by small mammals have a significant influence on vegetation patterns in the arid steppe vegetation of southern Mongolia?Location:Gobi Altay Mountains, southern Mongolia.Methods:We assessed the impact of the small lagomorphOchotona pallasion plant community composition, nutrient levels and biomass production in montane desert steppes. Data were derived from vegetation relevés, harvests of above‐ground standing crop and a bioassay, followed by analyses of soil and plant nutrient contents.Results:Although the local climate is arid with <150 mm annual precipitation, clear evidence of allogenic ecosystem engineering was found. Plant communities on burrows differed from those on undisturbed steppe in that they contained more species of annuals and dwarf shrubs, and a greater abundance of the important fodder grassAgropyron cristatum. Standing crop and nutrient concentrations were higher for plants growing on burrow soil.In situmeasurements and a pot experiment showed that this effect was related to increased levels of soil nutrients (P, K, N) rather than moisture availability.Conclusions:The study confirms thatO. pallasipositively influences soil nutrient levels on its burrows, which leads to increased grassland productivity even under dry conditions. Thus,O. pallasidoes not deteriorate site conditions, and the need for presently applied pest control schemes aimed at this species should be reassessed.
Differential effects of emergent Nothofagus dombeyi on growth and basal area of canopy species in an old‐growth temperate rainforest
Authors: Donoso Pablo J. , Lusk Christopher H. 
Published: February 2009

AbstractQuestion: Does overyielding of tree species mixtures in vertically stratified forests depend on complementary light use?Location: Andes of south‐central Chile.Methods: Basal area data were obtained from 80 circular plots distributed regularly throughout old‐growth stands with an emergent Nothofagus dombeyi tier over a canopy composed mainly of Laureliopsis philippiana and Saxegothaea conspicua. Radial growth was measured from cores obtained from trees at the centre of each plot. The effects of competition on growth were evaluated through a competition index (CI) based on distances to and diameters of the two nearest neighbours.Results: Overall, basal area of the canopy species was only weakly affected by the number of N. dombeyi per plot, and with basal area of N. dombeyi. However, the two main canopy species responded differently: whereas basal area of S. conspicua was negatively correlated with that of N. dombeyi, that of L. philippiana showed no response. Radial growth of S. conspicua was negatively correlated with CI calculated from canopy trees and more weakly so from emergent N. dombeyi. In contrast, radial growth of L. philippiana was not affected by competition with either canopy or emergent neighbours.Conclusions: Results indicate that emergent N. dombeyi tend to depress growth and basal area of S. conspicua, but not of the more shade‐tolerant L. philippiana. This supports the proposal that enhancement of wood production in stratified mixtures will be greatest when component species have strongly contrasting light use traits.
Multi‐species interactions in competitive hierarchies: New methods and empirical test
Authors: Perkins T. Alex , Holmes William R. , Weltzin Jake F. 
Published: February 2009

AbstractQuestion: Are competitive hierarchies, which are typically based on the results of pair‐wise competition experiments, sensitive to the level of species interaction in the underlying competition experiments?Location: Controlled greenhouse study using vegetation typical of old‐fields in East Tennessee, USA.Methods: We extend traditional competitive effect/response methods to incorporate data from competition experiments featuring any level of species interaction (i. e., 2, 3, …, n species interacting simultaneously) and develop an ordinal technique that makes hierarchies more robust to variation in the numerical values of relative yield. We apply these methodological techniques to empirical data from a greenhouse experiment wherein four old‐field plant species were grown in pair‐wise and tri‐wise combination. We also demonstrate how resampling can be used to determine the variability of data and its consequences for development of competitive hierarchies.Results: Different hierarchies were produced when we used different evaluation methods, different levels of species interaction, and different levels of replication. More acute resampling distributions and wider ranges of target/neighbor scores revealed that higher levels of species interaction lead to more distinct hierarchies.Conclusions: Hierarchies developed from interactions among subsets of species may inadequately characterize relationships among the full community because of indirect or higher‐order interactions within multi‐species assemblages. Different evaluation methods can yield different hierarchies, and resampling is an effective tool to determine the sensitivity of resultant hierarchies to the level of replication. In sum, our new methodology can be used to control uncertainty in poorly‐replicated experiments.
Multi‐stemmed trees in subtropical coastal dune forest: Survival strategy in response to chronic disturbance
Authors: Nzunda Emmanuel F. , Griffiths Megan E. , Lawes Michael J. 
Published: February 2009

AbstractQuestions: Is multi‐stemming a survival strategy in response to chronic disturbance? Is multi‐stemming under phylogenetic control? What environmental factors are associated with multi‐stemming? When do trees initiate growth of multiple stems? Do multi‐stemmed trees have limited stature?Location: Subtropical Indian Ocean coastal dune forest at Cape Vidal in the Greater St. Lucia Wetland Park, northeastern South Africa.Methods: Tree physiognomy and environmental conditions were sampled in 20 transects that were 300 m long and 5 m wide.Results: 38.9 % of trees were multi‐stemmed, with no correlation between multi‐stemming and taxonomic grouping. The multi‐stemming trait was most associated with stem decumb‐ency and substrate erosion and multi‐stemmed individuals were less common in protected dune slacks. Trees at Cape Vidal appear to facultatively produce multiple stems from an early stage. There was no trade‐off between tree height and stem number.Conclusions: Coastal winds and the unstable dune substrate are important environmental correlates of multi‐stemming. Both short stature and the high incidence of multi‐stemming are related to the tree‐disturbance interaction. The taxonomically widespread phenotypic plasticity in this trait indicates the importance of multi‐stemming to tree survival even under low levels of disturbance.
Upward shift of alpine plants increases floristic similarity of mountain summits
Authors: Jurasinski Gerald , Kreyling Jürgen 
Published: February 2009

AbstractQuestion: Does the upward shift of species and accompanied increase in species richness, induced by climate change, lead to homogenization of Alpine summit vegetation?Location: Bernina region of the Swiss Alps.Methods: Based on a data set from previous literature we expand the analysis from species richness to beta‐diversity and spatial heterogeneity. Species compositions of mountain summits are compared using a two‐component heterogeneity concept including the mean and the variance of Sørensen similarities calculated between the summits. Non‐metric multidimensional scaling is applied to explore developments of single summits in detail.Results: Both heterogeneity components (mean dissimilarity and variance) decrease over time, indicating a trend towards more homogeneous vegetation among Alpine summits. However, the development on single summits is not strictly unidirectional.Conclusions: The upward shift of plant species leads to homogenization of alpine summit regions. Thus, increasing alpha‐diversity is accompanied by decreasing beta‐diversity. Beta‐diversity demands higher recognition by scientists as well as nature conservationists as it detects changes which cannot be described using species richness alone.
Changing climate and historic‐woodland structure interact to control species diversity of the ‘Lobarion’ epiphyte community in Scotland
Authors: Ellis Christopher J. , Coppins Brian J. 
Published: February 2009

AbstractQuestion: How will changing climate and habitat structure interact to control the species diversity of lichen epiphytes?Location: Scotland.Method: Species richness (=diversity) of the epiphyte lichen community known as Lobarion (named after Lobaria pulmonaria) was quantified for 94 Populus tremula stands across Scotland, and compared in a predictive model to seven climate variables and eight measures of woodland structure. An optimum model was selected and used to project Lobarion diversity over the geographic range of the study area, based on IPCC climate change scenarios and hypothetical shifts in woodland structure.Results: Species diversity of the Lobarion community was best explained by three climate variables: (1) average annual temperature; (2) autumn and winter precipitation; in combination with (3) historic‐woodland extent. Projections indicate a positive effect of predicted climate change on Lobarion diversity, consistent with the physiological traits of cyanobac‐terial lichens comprising the Lobarion. However, the general response to climate is modified significantly by the effect on diversity of historic‐woodland extent.Conclusions: Historic‐woodland extent may exert an important control over local climate, as well as impacting upon the metapopulation dynamics of species in the Lobarion. In particular, a temporal delay in the response of Lobarion species to changed woodland structure is critical to our understanding of future climate change effects. Future Lobarion diversity (e.g. in the 2050s) may depend upon the interaction of contemporary climate (e.g. 2050s climate) and historic habitat structure (e.g. 1950s woodland extent). This is supported by previous observations for an extinction debt amongst lichen epiphytes, but suggests an extension of simple climate‐response models is necessary, before their wider application to lichen epiphyte diversity.
Natural avalanche disturbance shapes plant diversity and species composition in subalpine forest belt
Authors: Rixen Christian , Haag Susanne , Kulakowski Dominik , Bebi Peter 
Published: February 2009

AbstractBackground: Disturbances by avalanches have created unique habitats for animals and plants in subalpine ecosystems worldwide, but at the same time avalanches can pose a major threat to humans. Thus, avalanches are suppressed by means of avalanche barriers to protect settlements and infrastructures in populated areas of the European Alps. As a consequence, the disturbance regime in avalanche tracks has fundamentally changed.Methods: In the present study we address ecological consequences of avalanche suppression on plant diversity. We analysed plant diversity and species composition in recent and old avalanche tracks with and without avalanche suppression and in undisturbed adjacent forests at high and low elevations.Results: The number of species was higher in both active and inactive avalanche tracks as compared to undisturbed subalpine forest. The species composition indicated a wider range of ecological niches in active than in inactive avalanche tracks. The vegetation from active tracks showed lower indicator values for temperature and nitrogen availability. The proportion of alpine species was lower in formerly active tracks.Conclusions: The conditions that exist in active avalanche tracks increase plant diversity in relation to undisturbed forest. In the few decades following avalanche suppression, species composition changes in tracks from which avalanches have been excluded. Continued suppression of avalanche disturbance may lead to a decline in plant and habitat diversity. Avalanche disturbance can exert an important influence on the biodiversity of subalpine forests and provide important habitats. Anthropogenic changes in the natural regime of avalanche disturbance are likely to contribute significantly to future landscape changes in subalpine forests.
Improved estimates of incident radiation and heat load using non‐ parametric regression against topographic variables
Authors: McCune Bruce 
Published: February 2009

AbstractQuestion: Can non‐parametric multiplicative regression (NPMR) improve estimates of potential direct incident radiation (PDIR) and heat load based on topographic variables, as compared to least‐squares multiple regression against trigonometric transforms of the predictors?Methods: We used a multiplicative kernel smoothing technique to interpolate between tabulated values of PDIR, using a locally linear model and a Gaussian kernel, with slope, aspect, and latitude as predictors. Heat load was calculated as a 45 degree rotation of the PDIR response surface.Results: This method yielded a fit to a complex response surface with R2 > 0.99 and eliminated the areas of poor fit given by a previously published method based on least squares multiple regression with trigonometric functions of the predictors.Conclusions: Improved estimates of PDIR and heat load based on topographic variables can be obtained by using non‐parametric multiplicative regression (NPMR). The main drawback to the method is that it requires reference to the data tables, since those data are part of the model.