Browsing by Author "Von Gadow, Klaus"
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- ItemAnalysing taxonomic structures and local ecological processes in temperate forests in North Eastern China(BioMed Central, 2017) Fan, Chunyu; Tan, Lingzhao; Zhang, Chunyu; Von Gadow, KlausBackground: One of the core issues of forest community ecology is the exploration of how ecological processes affect community structure. The relative importance of different processes is still under debate. This study addresses four questions: (1) how is the taxonomic structure of a forest community affected by spatial scale? (2) does the taxonomic structure reveal effects of local processes such as environmental filtering, dispersal limitation or interspecific competition at a local scale? (3) does the effect of local processes on the taxonomic structure vary with the spatial scale? (4) does the analysis based on taxonomic structures provide similar insights when compared with the use of phylogenetic information? Based on the data collected in two large forest observational field studies, the taxonomic structures of the plant communities were analyzed at different sampling scales using taxonomic ratios (number of genera/number of species, number of families/number of species), and the relationship between the number of higher taxa and the number of species. Two random null models were used and the “standardized effect size” (SES) of taxonomic ratios was calculated, to assess possible differences between the observed and simulated taxonomic structures, which may be caused by specific ecological processes. We further applied a phylogeny-based method to compare results with those of the taxonomic approach. Results: As expected, the taxonomic ratios decline with increasing grain size. The quantitative relationship between genera/families and species, described by a linearized power function, showed a good fit. With the exception of the family-species relationship in the Jiaohe study area, the exponents of the genus/family-species relationships did not show any scale dependent effects. The taxonomic ratios of the observed communities had significantly lower values than those of the simulated random community under the test of two null models at almost all scales. Null Model 2 which considered the spatial dispersion of species generated a taxonomic structure which proved to be more consistent with that in the observed community. As sampling sizes increased from 20 m × 20 m to 50 m × 50 m, the magnitudes of SESs of taxonomic ratios increased. Based on the phylogenetic analysis, we found that the Jiaohe plot was phylogenetically clustered at almost all scales. We detected significant phylogenetically overdispersion at the 20 m × 20 m and 30 m × 30 m scales in the Liangshui plot. Conclusions: The results suggest that the effect of abiotic filtering is greater than the effects of interspecific competition in shaping the local community at almost all scales. Local processes influence the taxonomic structures, but their combined effects vary with the spatial scale. The taxonomic approach provides similar insights as the phylogenetic approach, especially when we applied a more conservative null model. Analysing taxonomic structure may be a useful tool for communities where well-resolved phylogenetic data are not available.
- ItemAnalysis of the global warming potential of biogenic CO₂ emission in life cycle assessments(Nature Research, 2017-01-03) Liu, Weiguo; Zhang, Zhonghui; Xie, Xinfeng; Yu, Zhen; Von Gadow, Klaus; Xu, Junming; Zhao, Shanshan; Yang, YuchunBiomass is generally believed to be carbon neutral. However, recent studies have challenged the carbon neutrality hypothesis by introducing metric indicators to assess the global warming potential of biogenic CO2 (GWPbio). In this study we calculated the GWPbio factors using a forest growth model and radiative forcing effects with a time horizon of 100 years and applied the factors to five life cycle assessment (LCA) case studies of bioproducts. The forest carbon change was also accounted for in the LCA studies. GWPbio factors ranged from 0.13–0.32, indicating that biomass could be an attractive energy resource when compared with fossil fuels. As expected, short rotation and fast-growing biomass plantations produced low GWPbio. Long-lived wood products also allowed more regrowth of biomass to be accounted as absorption of the CO2 emission from biomass combustion. The LCA case studies showed that the total life cycle GHG emissions were closely related to GWPbio and energy conversion efficiency. By considering the GWPbio factors and the forest carbon change, the production of ethanol and bio-power appeared to have higher GHG emissions than petroleum-derived diesel at the highest GWPbio.
- ItemAssessing biological dissimilarities between five forest communities(SpringerOpen (part of Springer Nature), 2019-06-06) Hao, Minhui; Corral-Rivas, J. J.; Gonzalez-Elizondo, M. S.; Ganeshaiah, K. N.; Nava-Miranda, M. G.; Zhang, Chunyu; Zhao, Xiuhai; Von Gadow, KlausBackground: Dissimilarity in community composition is one of the most fundamental and conspicuous features by which different forest ecosystems may be distinguished. Traditional estimates of community dissimilarity are based on differences in species incidence or abundance (e.g. the Jaccard, Sørensen, and Bray-Curtis dissimilarity indices). However, community dissimilarity is not only affected by differences in species incidence or abundance, but also by biological heterogeneities among species. Methods: The objective of this study is to present a new measure of dissimilarity involving the biological heterogeneity among species. The “discriminating Avalanche” introduced in this study, is based on the taxonomic dissimilarity between tree species. The application is demonstrated using observations from five stem-mapped forest plots in China and Mexico. We compared three traditional community dissimilarity indices (Jaccard, Sørensen, and Bray-Curtis) with the “discriminating Avalanche” index, which incorporates information, not only about species frequencies, but also about their taxonomic hierarchies. Results: Different patterns emerged for different measures of community dissimilarity. Compared with the traditional approaches, the discriminating Avalanche values showed a more realistic estimate of community dissimilarities, indicating a greater similarity among communities when species were closely related. Conclusions: Traditional approaches for assessing community dissimilarity disregard the taxonomic hierarchy. In the traditional analysis, the dissimilarity between Pinus cooperi and Pinus durangensis would be the same as the dissimilarity between P. cooperi and Arbutus arizonica. The dissimilarity Avalanche dissimilarity between P. cooperi and P. durangensis is considerably lower than the dissimilarity between P. cooperi and A. arizonica, because the taxonomic hierarchies are incorporated. Therefore, the discriminating Avalanche is a more realistic measure of community dissimilarity. This main result of our study may contribute to improved characterization of community dissimilarities.
- ItemClimate change effects in the Western Himalayan ecosystems of India : evidence and strategies(SpringerOpen, 2017) Tewari, Vindhya Prasad; Verma, Raj Kumar; Von Gadow, KlausBackground: The fragile landscapes of the Himalayan region are highly susceptible to natural hazards, and there is ongoing concern about current and potential climate change impacts. This study provides background information on India’s Western Himalayas and reviews evidence of warming as well as variability in precipitation and extreme events. Methods: Understanding and anticipating the impacts of climate change on Himalayan forest ecosystems and the services they provide to people are critical. Efforts to develop and implement effective policies and management strategies for climate change mitigation and adaptation requires particular new research initiatives. The various studies initiated and conducted in the region are compiled here. Results: Several new initiatives taken by the Himalayan Forest Research Institute in Shimla are described. This includes new permanent observational field studies, some with mapped trees, in high altitude transitional zones for continuous monitoring of vegetation response. We have also presented new strategies for mitigating potential climate change effects in Himalayan forest ecosystems. Conclusions: Assessment of the ecological and genetic diversity of the Himalayan conifers is required to evaluate potential responses to changing climatic conditions. Conservation strategies for the important temperate medicinal plants need to be developed. The impact of climate change on insects and pathogens in the Himalayas also need to be assessed. Coordinated efforts are necessary to develop effective strategies for adaptation and mitigation
- ItemComparing Johnson’s SBB, Weibull and Logit-Logistic bivariate distributions for modeling tree diameters and heights using copulas(Instituto Nacional de Investigacion y Tecnología Agraria y Alimentaria, 2016-04) Gorgoso-Varela, Jose J.; Garcia-Villabrille, Juan Daniel; Rojo-Alboreca, Alberto; Von Gadow, Klaus; Alvarez-Gonzalez, Juan GabrielAim of study: In this study we compare the accuracy of three bivariate distributions: Johnson’s SBB, Weibull-2P and LL-2P functions for characterizing the joint distribution of tree diameters and heights. Area of study: North-West of Spain. Material and methods: Diameter and height measurements of 128 plots of pure and even-aged Tasmanian blue gum (Eucalyptus globulus Labill.) stands located in the North-west of Spain were considered in the present study. The SBB bivariate distribution was obtained from SB marginal distributions using a Normal Copula based on a four-parameter logistic transformation. The Plackett Copula was used to obtain the bivariate models from the Weibull and Logit-logistic univariate marginal distributions. The negative logarithm of the maximum likelihood function was used to compare the results and the Wilcoxon signed-rank test was used to compare the related samples of these logarithms calculated for each sample plot and each distribution. Main results: The best results were obtained by using the Plackett copula and the best marginal distribution was the Logit-logistic. Research highlights: The copulas used in this study have shown a good performance for modeling the joint distribution of tree diameters and heights. They could be easily extended for modelling multivariate distributions involving other tree variables, such as tree volume or biomass.
- ItemDrivers of seedling survival in a temperate forest and their relative importance at three stages of succession(John Wiley & Sons Ltd., 2015-09-10) Yan, Yan; Zhang, Chunyu; Wang, Yuxi; Zhao, Xiuhai; Von Gadow, KlausNegative density dependence (NDD) and niche partitioning have been perceived as important mechanisms for the maintenance of species diversity. However, little is known about their relative contributions to seedling survival. We examined the effects of biotic and abiotic neighborhoods and the variations of biotic neighborhoods among species using survival data for 7503 seedlings belonging to 22 woody species over a period of 2 years in three different forest types, a half-mature forest (HF), a mature forest (MF), and an old-growth forest (OGF), each of these representing a specific successional stage in a temperate forest ecosystem in northeastern China. We found a convincing evidence for the existence of NDD in temperate forest ecosystems. The biotic and abiotic variables affecting seedlings survival change with successional stage, seedling size, and age. The strength of NDD for the smaller (<20 cm in height) and younger seedlings (1–2 years) as well as all seedlings combined varies significantly among species. We found no evidence that a community compensatory trend (CCT) existed in our study area. The results of this study demonstrate that the relative importance of NDD and habitat niche partitioning in driving seedling survival varies with seedling size and age and that the biotic and abiotic factors affecting seedlings survival change with successional stage.
- ItemEffects of density dependence in a temperate forest in northeastern China(Springer Nature, 2016-09-08) Yao, Jie; Zhang, Xinna; Zhang, Chunyu; Zhao, Xiuhai; Von Gadow, KlausENGLISH ABSTRACT: Negative density dependence may cause reduced clustering among individuals of the same species, and evidence is accumulating that conspecific density-dependent self-thinning is an important mechanism regulating the spatial structure of plant populations. This study evaluates that specific density dependence in three very large observational studies representing three successional stages in a temperate forest in northeastern China. The methods include standard spatial point pattern analysis and a heterogeneous Poisson process as the null model to eliminate the effects of habitat heterogeneity. The results show that most of the species exhibit conspecific density-dependent self-thinning. In the early successional stage 11 of the 16 species, in the intermediate successional stage 18 of the 21 species and in the old growth stage all 21 species exhibited density dependence after removing the effects of habitat heterogeneity. The prevalence of density dependence thus varies among the three successional stages and exhibits an increase with increasing successional stage. The proportion of species showing density dependence varied depending on whether habitat heterogeneity was removed or not. Furthermore, the strength of density dependence is closely related with species abundance. Abundant species with high conspecific aggregation tend to exhibit greater density dependence than rare species.
- ItemFunctional and phylogenetic diversity determine woody productivity in a temperate forest(Wiley Open Access, 2018) Hao, MinHui; Zhang, Chunyu; Zhao, Xiuhai; Von Gadow, KlausENGLISH ABSTRACT: Understanding the relationships between biodiversity and ecosystem productivity has become a central issue in ecology and conservation biology studies, particularly when these relationships are connected with global climate change and species extinction. However, which facets of biodiversity (i.e. taxonomic, functional, and phylogeneticdiversity) account most for variations in productivity are still not understood very well. This is especially true with regard to temperate forest ecosystems. In this study, we used a dataset from a stem- mapped permanent forest plot in northeastern China ex-ploring the relationships between biodiversity and productivity at different spatial scales (20 × 20 m; 40 × 40 m; and 60 × 60 m). The influence of specific environmental conditions (topographic conditions) and stand maturity (expressed by initial stand vol-ume and biomass) were taken into account using the multivariate approach known as structural equation models. The variable “Biodiversity” includes taxonomic (Shannon), functional (FDis), and phylogenetic diversity (PD). Biodiversity–productivity relation-ships varied with the spatial scales. At the scale of 20 × 20 m, PD and FDis significantly affected forest biomass productivity, while Shannon had only indirect effects. At the 40 × 40 m and 60 × 60 m scales, biodiversity and productivity were weakly correlated. The initial stand volume and biomass were the most important drivers of forest pro-ductivity. The local environmental conditions significantly influenced the stand vol-ume, biomass, biodiversity, and productivity. The results highlight the scale dependency of the relationships between forest biodiversity and productivity. The positive role of biodiversity in facilitating forest productivity was confirmed at the smaller scales. Our findings emphasize the fundamental role of environmental conditions in determining forest ecosystem performances. The results of this study provide a better understand-ing of the underlying ecological processes that influence specific forest biodiversity and productivity relationships.
- ItemHow beta diversity and the underlying causes vary with sampling scales in the Changbai mountain forests(John Wiley & Sons Ltd, 2017-10) Tan, Lingzhao; Fan, Chunyu; Zhang, Chunyu; Von Gadow, Klaus; Fan, XiuhuaENGLISH ABSTRACT: This study aims to establish a relationship between the sampling scale and tree species beta diversity temperate forests and to identify the underlying causes of beta diversity at different sampling scales. The data were obtained from three large observational study areas in the Changbai mountain region in northeastern China. All trees with a dbh ≥1 cm were stem-mapped and measured. The beta diversity was calculated for four different grain sizes, and the associated variances were partitioned into components explained by environmental and spatial variables to determine the contributions of environmental filtering and dispersal limitation to beta diversity. The results showed that both beta diversity and the causes of beta diversity were dependent on the sampling scale. Beta diversity decreased with increasing scales. The best-explained beta diversity variation was up to about 60% which was discovered in the secondary conifer and broad-leaved mixed forest (CBF) study area at the 40 × 40 m scale. The variation partitioning result indicated that environmental filtering showed greater effects at bigger grain sizes, while dispersal limitation was found to be more important at smaller grain sizes. What is more, the result showed an increasing explanatory ability of environmental effects with increasing sampling grains but no clearly trend of spatial effects. The study emphasized that the underlying causes of beta diversity variation may be quite different within the same region depending on varying sampling scales. Therefore, scale effects should be taken into account in future studies on beta diversity, which is critical in identifying different relative importance of spatial and environmental drivers on species composition variation.
- ItemSoil elements influencing community structure in an old-growth forest in Northeastern China(MDPI, 2016) Xu, Wei; Hao, Minhui; Wang, Juan; Zhang, Chunyu; Zhao, Xiuhai; Von Gadow, KlausENGLISH ABSTRACT: This study uses detailed soil and vegetation data collected in a 30-ha old-growth broad-leaved Korean pine forest to study the effect of soil properties on tree community structures. Spatial distribution patterns are simulated using a homogeneous Poisson process (HomP) and a homogeneous Thomas process (HomT). The simulated distributions are compared with the observed ones to explore correlations between certain tree species and several soil elements. The HomP model shows that all tested tree species are significantly correlated with at least one principal component in the upper-layer soil elements. The HomT model shows that only 36.4% of tree species are significantly correlated with the principal component of at least one upper-layer soil element. This result shows that the impact of dispersal limitation is greater than impact of environmental heterogeneity on species spatial distributions. The spatial autocorrelation of species induced by the dispersal limitation will largely conceal the plant-soil relationships caused by the heterogeneity of soil elements. An additional analysis shows that the elements in the upper soil layer which have the greatest impact on community niche structure are Pb, total phosphorus (TP), total nitrogen (TN), Cu, Cr, Zn and available nitrogen (AN). The corresponding elements in the lower soil layers are Pb, TP, Cu, organic carbon (OC), Mn, total potassium (TK) and AN. Different species seem to be complementary regarding the demands on the available soil resources. The results of this study show that the tree species in the different growth groups have different habitat preferences. Compared with subcanopy and shrub species, the canopy species have more significant correlations with the soil elements.
- ItemStoichiometry patterns in the androdioecious Acer tegmentosum(Springer Nature, 2016-10-11) Zhang, Xinna; Yao, Jie; Fan, Chunyu; Tan, Lingzhao; Zhang, Chunyu; Wang, Juan; Zhao, Xiuhai; Von Gadow, KlausENGLISH ABSTRACT: This study evaluates stoichiometry patterns in the androdioecious Acer tegmentosum, a species characterized by a rare reproductive system where males and hermaphrodites coexist. Altogether 31 hermaphrodites and 29 male plants were harvested and samples of leaves, current-year shoots, branches and coarse roots were analyzed to explore gender differences in biomass, C, N and P concentrations of these four components. The nitrogen to phosphorus relationship of each component was examined using SMA estimates. Males had significantly greater amounts of leaf and coarse root dry matter content than hermaphrodites. C, N and P stoichiometry differed significantly between genders, especially in the newly emerging vegetative components (leaves and shoots). Males had higher C/N and C/P ratios in current-year shoots and lower C/P ratios in leaves and branches. Hermaphrodites had higher N/P ratios in the leaves and branches. Males had higher rates of increase in leaf P content than hermaphrodites. This study suggests that stoichiometry patterns may be significantly affected by gender.