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Many recent studies have analysed plant species responses to environmental change, but interactive effects of global change drivers and how they are modulated by biotic interactions are still poorly understood. In a mesocosm experiment, we studied the interactive effects of nitrogen (N) fertilization and drought events on plant growth and how these effects are shaped by competitive interactions, using a segetal plant community typical of the lowlands of central Europe (composed of Lilium bulbiferum (segetal species) and Secale cereale (crop species)). We expected that N fertilization increases the drought sensitivity of Lilium (negative interaction effect), and that these effects are shaped by interspecific competition with Secale. Secale and Lilium showed opposing responses to N fertilization (second year of the experiment): Whilst Secale aboveground and belowground biomass almost doubled with N fertilization, Lilium aboveground and belowground biomass showed no response or decreased, respectively, providing Secale with a competitive advantage. Lilium aboveground tissue dieback (as a proxy for growth vigour) was 22% in N and 35% in drought treatments (control: 6%), but reached 91% when combining these treatments. Increasing Lilium tissue dieback was strongly related to decreasing belowground (root) biomass, caused by both negative direct effects of combined treatments (N fertilization + drought), and negative indirect effects acting via treatment-induced increase in Secale biomass. Our results demonstrate that competitive interactions can shape the effects of global change drivers on plant growth. This knowledge in turn could be important for plant species conservation, particularly in the face of ongoing shifts in environmental conditions.

Background and Aims In addition to terrestrial laser scanning (TLS), mobile laser scanning (MLS) is increasingly arousing interest as a technique which provides valuable 3-D data for various applications in forest research. Using mobile platforms, the 3-D recording of large forest areas is carried out within a short space of time. Vegetation structure is described by millions of 3-D points which show an accuracy in the millimetre range and offer a powerful basis for automated vegetation modelling. The successful extraction of single trees from the point cloud is essential for further evaluations and modelling at the individual-tree level, such as volume determination, quantitative structure modelling or local neighbourhood analyses. However, high-precision automated tree segmentation is challenging, and has so far mostly been performed using elaborate interactive segmentation methods. Methods Here, we present a novel segmentation algorithm to automatically segment trees in MLS point clouds, applying distance adaptivity as a function of trajectory. In addition, tree parameters are determined simultaneously. In our validation study, we used a total of 825 trees from ten sample plots to compare the data of trees segmented from MLS data with manual inventory parameters and parameters derived from semi-automatic TLS segmentation. Key Results The tree detection rate reached 96 % on average for trees with distances up to 45 m from the trajectory. Trees were almost completely segmented up to a distance of about 30 m from the MLS trajectory. The accuracy of tree parameters was similar for MLS-segmented and TLS-segmented trees. Conclusions Besides plot characteristics, the detection rate of trees in MLS data strongly depends on the distance to the travelled track. The algorithm presented here facilitates the acquisition of important tree parameters from MLS data, as an area-wide automated derivation can be accomplished in a very short time.

Though competition operates distinctly above and below ground, competition with near neighbours explained more variation in crown and root system morphology of young tropical trees than did abiotic conditions. Comparisons of above- and below-ground tree architecture and variation remain scarce in the literature of competition dynamics in forests. Trees compete above and below ground with neighbours, but the extent of such a neighbourhood and the relative importance of above- or below-ground neighbours in determining tree growth rates remain poorly understood. We combined terrestrial laser scans and a root excavation campaign in the tropical planted Sardinilla forest experiment with annual diameter-at-breast height measurements to test how the crowns and root systems of five tropical tree species (N = 128) varied with biotic neighbourhood and abiotic environmental characteristics. Crown and root system extent were compared, and the Hegyi competition index calculated at three spatial scales was regressed on focal tree biomass. We identified which neighbourhood and environmental variables explained most of the variation in mean crown and root system extent and compactness (a measure of morphological homogeneity) at the plot level and for species separately. Root systems were 2.6 ± 1.1 times wider than crowns on average and focal tree biomass was the best predicted by competition with near neighbours. At the plot level, more variation in crown and root system traits was explained by biotic than abiotic characteristics (65.8 and 26.0%, respectively). More intense competition in the near neighbourhood reduced crown extent of one study species (Anacardium excelsum) and root system extent of 4 out of 5 study species, and it also led to more compact crowns and root systems of Tabebuia rosea. After accounting for spatial autocorrelation in focal tree location, soil nitrogen concentration was not found to significantly affect the studied morphological traits. These results emphasize the role of competition in determining tree morphology generally, while also supporting the claim that competition operates distinctly above and below ground.

With progressing climate change, increasing weather extremes will endanger tree regeneration. Canopy openings provide light for tree establishment, but also reduce the microclimatic buffering effect of forests. Thus, disturbances can have both positive and negative impacts on tree regeneration. In 2015, three years before an extreme drought episode hit Central Europe, we established a manipulation experiment with a factorial block design in European beech (Fagus sylvatica L.)-dominated forests. At five sites located in southeastern Germany, we conducted three censuses of tree regeneration after implementing two different canopy disturbances (aggregated and distributed canopy openings), and four deadwood treatments (retaining downed, standing, downed + standing deadwood and removing all deadwood), as well as in one untreated control plot. In addition, we measured understory light levels and recorded local air temperature and humidity over five years. We (i) tested the effects of experimental disturbance and deadwood treatments on regeneration and (ii) identified the drivers of regeneration density as well as seedling species and structural diversity. Regeneration density increased over time. Aggregated canopy openings supported species and structural diversity, but reduced regeneration density. Tree regeneration was positively associated with understory light levels, while maximum vapor pressure deficit influenced tree regeneration negatively. Deadwood and browsing impacts on regeneration varied and were inconclusive. Our study indicates that despite the drought episode regeneration in beech-dominated forests persisted under moderately disturbed canopies. However, the positive effect of increased light availability on tree regeneration might have been offset by harsher microclimate after canopies have been disturbed.

Plant diversity loss can alter higher trophic -level communities via non -random species interactions, which in turn may cascade to affect key ecosystem func-tions. These non -random linkages might be best captured by patterns of phyloge-netic diversity, which take into account co -evolutionary dependencies. However,lack of adequate phylogenetic data of higher trophic levels hampers our mecha-nistic understanding of biodiversity relationships in species-rich ecosystems.2. We used DNA barcoding to generate data on the phylogenetic diversity of lepi-dopteran caterpillars in a large- scale forest biodiversity experiment in subtropicalChina. We analysed how different metrics of lepidopteran phylogenetic diversity(Faith's PD, MPD, MNTD) and taxonomic diversity were influenced by multiple components of tree diversity (taxonomic, functional, phylogenetic).3. Our data from six sampling periods represent 7,204 mitochondrial cytochrome c oxidase subunit I (COI) sequences of lepidopteran larvae, clustered into 461 mo-lecular operational taxonomic units. Lepidopteran abundance, the effective num-ber of species (irrespective of the focus on rare or common species) and Faith's PD and MPD (reflecting basal evolutionary splits), but not MNTD (reflecting re-cent evolutionary splits), significantly increased with experimentally manipulated ree species richness. Lepidopteran MNTD decreased with increasing tree MNTD. Path analyses showed that tree phylogenetic and functional diversity explained part, but not all of the effects of tree species richness on lepidopteran diversity. Importantly, tree diversity effects on lepidopteran diversity were to a large extent indirect, operating via changes in lepidopteran abundance. 4. Synthesis. Our study shows that evolutionary dependencies determine the response of herbivore communities to changes in host plant diversity. Incorporating a wider range of diversity metrics both at the level of producers and consumers can thus help to develop a more comprehensive understanding of the functional consequences of biodiversity change across trophic levels. Moreover, the dependence of trophic linkages on herbivore abundances underlines the need to address the consequences of current declines in insect abundances for ecosystem structure and functioning. peerReviewed

Forest liming is often used as a mitigation tool to counteract soil acidification that is caused by atmospheric deposition. However, our understanding of the long-term effects of liming on forest communities is still incomplete. We examine the effects of repeated liming on the herb layer of spruce stands in the Ore Mountains in East Germany. The area is characterised by acidic bedrock and profound soil acidification caused by high levels of anthropogenic sulphur deposition in the late twentieth century. Lime has been applied as part of forest management since 1988. We created a stratified sample in which we recorded vegetation releves covering spruce stands without liming (L0) and with one to five lime applications (L1–L5). We found a positive correlation between liming intensity and alpha diversity. Most of the indicator species were identified for spruce stands with high liming intensity (L2–L5), but no indicators were found for unlimed stands. From the third liming, the impact of lime application on species diversity and composition saturated. Several of the species promoted by liming are typical for mature stands of the natural vegetation but had declined in the twentieth century. Thus, a slight trend towards the restoration of the natural vegetation can be seen after liming. However, this is contrasted with a strong increase in species that are disturbance indicators (i.e. species of nitrogen-rich soils and open habitats). Continuation of liming as part of regular forestry management will cause these effects to establish permanently over large areas. Based on these findings, we make suggestions to adapt forest management strategies.

Biodiversity is considered to mitigate detrimental impacts of climate change on the functioning of forest ecosystems, such as drought-induced decline in forest productivity. However, previous studies produced controversial results and experimental evidence is rare. Specifically, the biological mechanisms underlying mitigation effects remain unclear, as existing work focuses on biodiversity effects related to the community scale. Using trait-based neighbourhood models, we quantified changes in above-ground wood productivity of 3,397 trees that were planted in a large-scale tree diversity experiment in subtropical China across gradients of neighbourhood diversity and climatic conditions over a 6-year period. This approach allowed us to simultaneously assess to what extent functional traits of a focal tree and biodiversity at the local neighbourhood scale mediate the growth response of individual trees to drought events. We found that neighbourhood tree species richness can mitigate for drought-induced growth decline of young trees. Overall, positive net biodiversity effects were strongest during drought and increased with increasing taxonomic diversity of neighbours. In particular, drought-sensitive species (i.e. those with a low cavitation resistance) benefitted the most from growing in diverse neighbourhoods, suggesting that soil water partitioning among local neighbours during drought particularly facilitated most vulnerable individuals. Thus, diverse neighbourhoods may enhance ecosystem resistance to drought by locally supporting drought-sensitive species in the community. Synthesis. Our findings demonstrate that mechanisms operating at the local neighbourhood scale are a key component for regulating forests responses to drought and improve insights into how local species interactions vary along stress gradients in highly diverse tree communities.

A large proportion of temperate forest plant diversity is found in the herb layer.However, for many of its species, little is known about their autecology, whichmakes it difficult to assess potential threats and efficiently safeguard the diversity of understorey herbaceous communities. This also applies to Gageaspathacea (Liliaceae), a globally rare spring geophyte, which mainly occurs indeciduous forests of northern Central Europe. We investigated the causal relationships between population characteristics of G. spathacea and abiotic siteconditions across different forest communities in the center of its distributionalrange. Leaf length (a surrogate of the species' vegetative propagation) was positively related to soil moisture and soil nitrogen. Consequently, mean leaflength was highest in moist forest communities of the alliance Alno-Ulmion.Moreover, mean variability in leaf length was lowest in those forests, indicatinga higher and more stable vegetative propagation via bulbils. We found no support for a significant relationship between leaf length and leaf density orbetween leaf length and flower formation. Population density varied stronglyamong forest sites, but was not related to soil moisture and hardly influenced by soil nitrogen. Our results suggest that soil water and nutrient supply play avital role in determining the species' vegetative propagation, whereas the duration of habitat continuity is most likely an important determinant of population size and density. Conservation strategies therefore require a betterunderstanding of the complex interrelationships between abiotic site conditionsand the historical context-dependency of habitats. A large proportion of temperate forest plant diversity is found in the herb layer. However, for many of its species, little is known about their autecology, which makes it difficult to assess potential threats and efficiently safeguard the diversity of understorey herbaceous communities. This also applies to Gagea spathacea (Liliaceae), a globally rare spring geophyte, which mainly occurs in deciduous forests of northern Central Europe. We investigated the causal relationships between population characteristics of G. spathacea and abiotic site conditions across different forest communities in the center of its distributional range. Leaf length (a surrogate of the species' vegetative propagation) was positively related to soil moisture and soil nitrogen. Consequently, mean leaf length was highest in moist forest communities of the alliance Alno‐Ulmion. Moreover, mean variability in leaf length was lowest in those forests, indicating a higher and more stable vegetative propagation via bulbils. We found no support for a significant relationship between leaf length and leaf density or between leaf length and flower formation. Population density varied strongly among forest sites, but was not related to soil moisture and hardly influenced by soil nitrogen. Our results suggest that soil water and nutrient supply play a vital role in determining the species' vegetative propagation, whereas the duration of habitat continuity is most likely an important determinant of population size and density. Conservation strategies therefore require a better understanding of the complex interrelationships between abiotic site conditions and the historical context‐dependency of habitats.

International audience; Variations in crown forms promote canopy space-use and productivity in mixed-species forests. However, we have a limited understanding on how this response is mediated by changes in within-tree biomass allocation. Here, we explored the role of changes in tree allometry, biomass allocation and architecture in shaping diversity-productivity relationships (DPRs) in the oldest tropical tree diversity experiment. We conducted whole-tree destructive biomass measurements and terrestrial laser scanning. Spatially explicit models were built at the tree level to investigate the effects of tree size and local neighbourhood conditions. Results were then upscaled to the stand level, and mixture effects were explored using a bootstrapping procedure. Biomass allocation and architecture substantially changed in mixtures, which resulted from both tree-size effects and neighbourhood-mediated plasticity. Shifts in biomass allocation among branch orders explained substantial shares of the observed overyielding. By contrast, root-to-shoot ratios, as well as the allometric relationships between tree basal area and aboveground biomass, were little affected by the local neighbourhood. Our results suggest that generic allometric equations can be used to estimate forest aboveground biomass overyielding from diameter inventory data. Overall, we demonstrate that shifts in tree biomass allocation are mediated by the local neighbourhood and promote DPRs in tropical forests.

1. Understanding how species diversity affects plant performance is a central question in biodiversity–ecosystem functioning (BEF) research. At the community level, functional trait means and trait dissimilarities have been used to explain biodiversity effects, but with mixed success. To disentangle how functional traits explain community growth and underpin biodiversity–ecosystem functioning relationships, we should elucidate how plant traits affect individual growth across species richness levels, because the role of functional traits on growth depends on the ecological context of the individual.2. We addressed this topic by using detailed data of twelve functional traits and annual growth for 529 individual trees of 31 species at five species‐richness levels in a large forest biodiversity experiment in south‐east China from 4 to 9 years after planting.3. Our analyses show first that individual trait values can change with species richness, indicating that trait values can change due to the biotic context. Secondly, we show that early tree growth is more strongly affected by traits than by species richness. Finally, our data show that growth–trait relationships can change with species richness and with forest age. Trait effects on growth are more pronounced at higher richness levels, indicating that measuring traits on individual trees across richness levels can improve growth predictions and inference of BEF relationships that are shaped by functional traits.4. Synthesis. This study shows that functional trait values and their effect on individual tree growth depend on species richness. Our data support the notion that to elucidate how functional traits shape biodiversity–ecosystem functioning relationships, an important step is to consider the biotic context of individual trees within a community. We have made an initial step by analysing how functional traits affect individual‐tree growth in a diversity‐dependent manner and future research should continue by elucidating the role of traits on tree–tree interactions across diversity levels. 1. Understanding how species diversity affects plant performance is a central question in biodiversity–ecosystem functioning (BEF) research. At the community level, functional trait means and trait dissimilarities have been used to explain biodiversity effects, but with mixed success. To disentangle how functional traits explain community growth and underpin biodiversity–ecosystem functioning relationships, we should elucidate how plant traits affect individual growth across species richness levels, because the role of functional traits on growth depends on the ecological context of the individual.2. We addressed this topic by using detailed data of twelve functional traits and annual growth for 529 individual trees of 31 species at five species‐richness levels in a large forest biodiversity experiment in south‐east China from 4 to 9 years after planting.3. Our analyses show first that individual trait values can change with species richness, indicating that trait values can change due to the biotic context. Secondly, we show that early tree growth is more strongly affected by traits than by species richness. Finally, our data show that growth–trait relationships can change with species richness and with forest age. Trait effects on growth are more pronounced at higher richness levels, indicating that measuring traits on individual trees across richness levels can improve growth predictions and inference of BEF relationships that are shaped by functional traits.4. Synthesis. This study shows that functional trait values and their effect on individual tree growth depend on species richness. Our data support the notion that to elucidate how functional traits shape biodiversity–ecosystem functioning relationships, an important step is to consider the biotic context of individual trees within a community. We have made an initial step by analysing how functional traits affect individual‐tree growth in a diversity‐dependent manner and future research should continue by elucidating the role of traits on tree–tree interactions across diversity levels.

AimsGrowth rates of plants are driven by factors that influence the amount of resources captured and the efficiency of resource use. In trees, the amount of light captured and the efficiency of light use strongly depends on crown characteristics and leaf traits. Although theory predicts that both crown and leaf traits affect tree growth, few studies have yet to integrate these two types of traits to explain species-specific growth rates. Using 37 broad-leaved tree species of subtropical forests in SE China, we investigated how interspecific differences in wood volume growth rates were affected by crown and leaf traits. We tested the hypotheses that (i) larger crown dimensions promote growth rates, (ii) species-specific growth rates are positively related to leaf stomatal conductance, leaf water potential and leaf chemical components, and negatively related to leaf C/N and leaf toughness and (iii) the two sets of traits better explain growth rates in combination than either alone.MethodsOur study was conducted in a large-scale forest Biodiversity and Ecosystem Functioning experiment in China (BEF-China), located in a mountainous region in Jiangxi Province. We related 17 functional traits (two crown dimension and three crown structure traits; six physiological and six morphological leaf traits) to the mean annual growth rate of wood volume of young trees of the studied species. Interrelationships between crown and leaf traits were analyzed using principal component analysis. Simple linear regression analysis was used to test the effect of each trait separately. We used multiple regression analysis to establish the relationship of growth rate to each set of traits (crown traits, physiological and morphological leaf traits) and to the combination of all types of traits. The coefficients of determination (R2adj) of the best multiple regression models were compared to determine the relative explanatory power of crown and leaf traits and a combination of both.Important FindingsThe species-specific growth rates were not related to any of the single crown traits, but were related positively to leaf stomatal conductance and leaf water potential individually, and negatively to leaf toughness, with approximately 13% variance explained by each of the traits. Combinations of different crown traits did not significantly explain the species-specific growth rates, whereas combinations of either physiological or morphological leaf traits explained 24% and 31%, respectively. A combination of both crown and leaf traits explained 42% of variance in species-specific growth rates. We concluded that sets of traits related to carbon assimilation at the leaf-level and to overall amount of leaves exposed at the crown-level jointly explained species-specific growth rates better than either set of traits alone.

Aims Although the net biodiversity effect (NE) can be statistically partitioned into complementarity and selection effects (CE and SE), there are different underlying mechanisms that can cause a certain partitioning. Our objective was to assess the role of resource partitioning and species interactions as two important mechanisms that can bring about CEs by interspecific and intraspecific trait variation. Methods We measured tree height of 2493 living individuals in 57 plots and specific root length (SRL) on first-order roots of 368 of these individuals across different species richness levels (1, 2, 4, 8 species) in a large-scale forest biodiversity and ecosystem functioning experiment in subtropical China (BEF-China) established in 2009. We describe the effects of resource partitioning between species by a fixed component of interspecific functional diversity (RaoQ) and further effects of species interactions by variable components of interspecific and intraspecific functional diversity (community weighted trait similarity and trait dissimilarity, CWS and CWD). Finally, we examined the relationships between biodiversity effects on stand-level tree height and functional diversity (RaoQ, CWS and CWD) in SRL using linear regression and assessed the relative importance of these three components of functional diversity in explaining the diversity effects. Important Findings Our results show that species richness significantly affected SRL in five and tree height in ten out of 16 species. A positive NE was generally brought about by a positive CE on stand-level tree height and related to high values of RaoQ and CWS in SRL. A positive CE was related to high values of all three components of root functional diversity (RaoQ, CWS and CWD). Our study suggests that both resource partitioning and species interactions are the underlying mechanisms of biodiversity effects on stand-level tree growth in subtropical forest.

Climate change and atmospheric deposition of nitrogen affect biodiversity patterns and functions of forest ecosystems worldwide. Many studies have quantified tree growth responses to single global change drivers, but less is known about the interaction effects of these drivers at the plant and ecosystem level. In the present study, we conducted a full-factorial greenhouse experiment to analyse single and combined effects of nitrogen fertilization (N treatment) and drought (D treatment) on 16 morphological and chemical response variables (including tissue δ13C signatures) of one-year-old Fagus sylvatica seedlings originating from eight different seed families from the Cantabrian Mountains (NW Spain). Drought exerted the strongest effect on response variables, reflected by decreasing biomass production and increasing tissue δ13C signatures. However, D and N treatments interacted for some of the response variables, indicating that N fertilization has the potential to strengthen the negative effects of drought (with both antagonistic and amplifying interactions). For example, combined effects of N and D treatments caused a sevenfold increase of necrotic leaf biomass. We hypothesize that increasing drought sensitivity was mainly attributable to a significant reduction of the root biomass in combined N and D treatments, limiting the plants’ capability to satisfy their water demands. Significant seed family effects and interactions of seed family with N and D treatments across response variables suggest a high within-population genetic variability. In conclusion, our findings indicated a high drought sensitivity of Cantabrian beech populations, but also interaction effects of N and D on growth responses of beech seedlings.

Despite the importance of herbivory for the structure and functioning of species-rich forests, little is known about how herbivory is affected by tree species richness, and more specifically by random vs. non-random species loss.We assessed herbivore damage and its effects on tree growth in the early stage of a large-scale forest biodiversity experiment in subtropical China that features random and non-random extinction scenarios of tree mixtures numbering between one and 24 species. In contrast to random species loss, the non-random extinction scenarios were based on the tree species' local rarity and specific leaf area – traits that may strongly influence the way herbivory is affected by plant species richness.Herbivory increased with tree species richness across all scenarios and was unaffected by the different species compositions in the random and non-random extinction scenarios. Whereas tree growth rates were positively related to herbivory on plots with smaller trees, growth rates significantly declined with increasing herbivory on plots with larger trees. Our results suggest that the effects of herbivory on growth rates increase from monocultures to the most species-rich plant communities and that negative effects with increasing tree species richness become more pronounced with time as trees grow larger.Synthesis. Our results indicate that key trophic interactions can be quick to become established in forest plantations (i.e. already 2.5 years after tree planting). Stronger herbivory effects on tree growth with increasing tree species richness suggest a potentially important role of herbivory in regulating ecosystem functions and the structural development of species-rich forests from the very start of secondary forest succession. The lack of significant differences between the extinction scenarios, however, contrasts with findings from natural forests of higher successional age, where rarity had negative effects on herbivory. This indicates that the effects of non-random species loss could change with forest succession.

The effects of atmospheric nitrogen (N) deposition on ecosystem functioning largely depend on the retention of N in different ecosystem compartments, but accumulation and partitioning processes have rarely been quantified in long-term field experiments. In the present study we analysed for the first time decadal-scale flows and allocation patterns of N in a heathland ecosystem that has been subject to airborne N inputs over decades. Using a long-term 15N tracer experiment, we quantified N retention and flows to and between ecosystem compartments (above-ground/below-ground vascular biomass, moss layer, soil horizons, leachate). After 9 years, about 60% of the added 15N-tracer remained in the N cycle of the ecosystem. The moss layer proved to be a crucial link between incoming N and its allocation to different ecosystem compartments (in terms of a short-term capture, but long-term release function). However, about 50% of the 15N captured and released by the moss layer was not compensated for by a corresponding increase in recovery rates in any other compartment, probably due to denitrification losses from the moss layer in the case of water saturation after rain events. The O-horizon proved to be the most important long-term sink for added 15N, as reflected by an increase in recovery rates from 18 to 40% within 8 years. Less than 2.1% of 15N were recovered in the podzol-B-horizon, suggesting that only negligible amounts of N were withdrawn from the N cycle of the ecosystem. Moreover, 15N recovery was low in the dwarf shrub above-ground biomass (

In the original publication of the article, the Table 2 column heading that reads “L6” should read “SB” and the ORCID iD of the fourth author was missed in the original publication and included in this correction.

AimsThe aim of our research was to understand small-scale effects of topography and soil fertility on tree growth in a forest biodiversity and ecosystem functioning (BEF) experiment in subtropical SE China.MethodsGeomorphometric terrain analyses were carried out at a spatial resolution of 5×5 m. Soil samples of different depth increments and data on tree height were collected from a total of 566 plots (667 m2 each). The soils were analyzed for carbon (soil organic carbon [SOC]), nitrogen, acidity, cation exchange capacity (CEC), exchangeable cations and base saturation as soil fertility attributes. All plots were classified into geomorphological units. Analyses of variance and linear regressions were applied to all terrain, soil fertility and tree growth attributes.Important FindingsIn general, young and shallow soils and relatively small differences in stable soil properties suggest that soil erosion has truncated the soils to a large extent over the whole area of the experiment. This explains the concurrently increasing CEC and SOC stocks downslope, in hollows and in valleys. However, colluvial, carbon-rich sediments are missing widely due to the convexity of the footslopes caused by uplift and removal of eroded sediments by adjacent waterways. The results showed that soil fertility is mainly influenced by topography. Monte–Carlo flow accumulation (MCCA), curvature, slope and aspect significantly affected soil fertility. Furthermore, soil fertility was affected by the different geomorphological positions on the experimental sites with ridge and spur positions showing lower exchangeable base cation contents, especially potassium (K), due to leaching. This geomorphological effect of soil fertility is most pronounced in the topsoil and decreases when considering the subsoil down to 50cm depth. Few soil fertility attributes affect tree height after 1–2 years of growth, among which C stocks proved to be most important while pHKCl and CEC only played minor roles. Nevertheless, soil acidity and a high proportion of Al on the exchange complex affected tree height even after only 1–2 years growth. Hence, our study showed that forest nutrition is coupled to a recycling of litter nutrients, and does not only depend on subsequent supply of nutrients from the mineral soil. Besides soil fertility, topography affected tree height. We found that especially MCCA as indicator of water availability affected tree growth at small-scale, as well as aspect. Overall, our synthesis on the interrelation between fertility, topography and tree growth in a subtropical forest ecosystem in SE China showed that topographic heterogeneity lead to ecological gradients across geomorphological positions. In this respect, small-scale soil–plant interactions in a young forest can serve as a driver for the future development of vegetation and biodiversity control on soil fertility. In addition, it shows that terrain attributes should be accounted for in ecological research.

Understanding how trees respond to global change drivers is central to predict changes in forest structure and functions. Although there is evidence on the mode of nitrogen (N) and drought (D) effects on tree growth, our understanding of the interplay of these factors is still limited. Simultaneously, as mixtures are expected to be less sensitive toglobal change as compared to monocultures, we aimed to investigate the combined effects of N addition and D on the productivity of three tree species (Fagus sylvatica, Quercus petraea, Pseudotsuga menziesii) in relation to functional diverse species mixtures using data from a 4-year field experiment in Northwest Germany. Here we show that species mixing can mitigate the negative effects of combined N fertilizationand D events, but the community response is mainly driven by the combination of certain traits rather than the tree species richness of a community. For beech, we found that negative effects of D on growth rates were amplified by N fertilization (i.e., combined treatment effects were non-additive), while for oak and fir, the simultaneous effects of Nand D were additive. Beech and oak were identified as most sensitive to combined NCD effects with a strong size-dependency observed for beech, suggesting that the negative impact of NCD becomes stronger with time as beech grows larger. As a consequence, the net biodiversity effect declined at the community level, which can be mainly assignedto a distinct loss of complementarity in beech-oak mixtures. This pattern, however, was not evident in the other species-mixtures, indicating that neighborhood composition (i.e., trait combination), but not tree species richness mediated the relationship between tree diversity and treatment effects on tree growth. Our findings point to the importance of the qualitative role (‘trait portfolio’) that biodiversity play in determining resistance of diverse tree communities to environmental changes. As such, they provide further understanding for adaptive management strategies in the context of global change. Understanding how trees respond to global change drivers is central to predict changes in forest structure and functions. Although there is evidence on the mode of nitrogen (N) and drought (D) effects on tree growth, our understanding of the interplay of these factors is still limited. Simultaneously, as mixtures are expected to be less sensitive to global change as compared to monocultures, we aimed to investigate the combined effects of N addition and D on the productivity of three tree species (Fagus sylvatica, Quercus petraea, Pseudotsuga menziesii) in relation to functional diverse speciesmixtures using data from a 4-year field experiment in Northwest Germany. Here we show that species mixing can mitigate the negative effects of combined N fertilization and D events, but the community response is mainly driven by the combination of certain traits rather than the tree species richness of a community. For beech, we found that negative effects of D on growth rates were amplified by N fertilization (i.e., combined treatment effects were non-additive), while for oak and fir, the simultaneous effects of N and D were additive. Beech and oak were identified as most sensitive to combined NCDeffects with a strong size-dependency observed for beech, suggesting that the negative impact of NCD becomes stronger with time as beech grows larger. As a consequence, the net biodiversity effect declined at the community level, which can be mainly assigned to a distinct loss of complementarity in beech-oak mixtures. This pattern, however, was not evident in the other species-mixtures, indicating that neighborhood composition (i.e., trait combination), but not tree species richness mediated the relationship between tree diversity and treatment effects on tree growth. Our findings point to the importance of the qualitative role (‘trait portfolio’) that biodiversity play in determining resistance of diverse tree communities to environmental changes. As such, they provide further understanding for adaptive management strategies in the context of global change.

We investigated the response of the perennialgrass Molinia caerulea (L.) Moench to combinedeffects of fertilization (N, P) and drought events. Wehypothesized that N fertilization increases, anddrought decreases productivity, but that N additionstrengthens negative effects caused by drought.Methods Within a full-factorial 2-year greenhouseexperiment we measured biomass productivity andallocation, tissue nutrient concentrations and nitrogenallocation patterns using 15N as a tracer.Results N fertilization caused a strong increase inproductivity, but effects of drought were almostinsignificant. However, we found strongly interrelated,non-additive effects of fertilization and drought,expressed by a strong increase of necrotic tissue.Dead aboveground biomass showed the highestvalues for N and 15N.Conclusions Accelerated productivity of abovegroundtissue under N fertilization resulted in increased evaporativedemands and thus higher drought susceptibility.In addition 15N allocation patterns showed thatfertilization-drought treatments disenabled plants’control of their N allocation. Molinia was unable towithdraw leaf N during the dieback of abovegroundtissue. Due to the lack of an adaptive strategy to thecombined effects of fertilization and drought, increasingsummer drought may weaken the competitiveperformance of species with traits comparable tothose of Molinia in N-fertilized environments. We investigated the response of the perennialgrass Molinia caerulea (L.) Moench to combinedeffects of fertilization (N, P) and drought events. Wehypothesized that N fertilization increases, anddrought decreases productivity, but that N additionstrengthens negative effects caused by drought.Methods Within a full-factorial 2-year greenhouseexperiment we measured biomass productivity andallocation, tissue nutrient concentrations and nitrogenallocation patterns using 15N as a tracer.Results N fertilization caused a strong increase inproductivity, but effects of drought were almostinsignificant. However, we found strongly interrelated,non-additive effects of fertilization and drought,expressed by a strong increase of necrotic tissue.Dead aboveground biomass showed the highestvalues for N and 15N.Conclusions Accelerated productivity of abovegroundtissue under N fertilization resulted in increased evaporativedemands and thus higher drought susceptibility.In addition 15N allocation patterns showed thatfertilization-drought treatments disenabled plants’control of their N allocation. Molinia was unable towithdraw leaf N during the dieback of abovegroundtissue. Due to the lack of an adaptive strategy to thecombined effects of fertilization and drought, increasingsummer drought may weaken the competitiveperformance of species with traits comparable tothose of Molinia in N-fertilized environments.

Summary 1. Insect herbivory can strongly affect ecosystem processes, and its relationship with plant diversity is a central topic in biodiversity–functioning research. However, very little is known about this relationship from complex ecosystems dominated by long-lived individuals, such as forests, especially over gradients of high plant diversity. 2. We analysed insect herbivory on saplings of 10 tree and shrub species across 27 forest stands differing in age and tree species richness in an extraordinarily diverse subtropical forest ecosystem in China. We tested whether plant species richness significantly influences folivory in these highly diverse forests or whether other factors play a more important role at such high levels of phytodiversity. 3. Leaf damage was assessed on 58 297 leaves of 1284 saplings at the end of the rainy season in 2008, together with structural and abiotic stand characteristics. 4. Species-specific mean damage of leaf area ranged from 3% to 16%. Herbivory increased with plant species richness even after accounting for potentially confounding effects of stand characteristics, of which stand age-related aspects most clearly covaried with herbivory. Intraspecific density dependence or other abiotic factors did not significantly influence overall herbivory across forest stands. 5. Synthesis. The positive herbivory–plant diversity relationship indicates that effects related to hypotheses of resource concentration, according to which a reduction in damage by specialized herbivores might be expected as host plant concentration decreases with increasing plant diversity, do not seem to be major determinants for overall herbivory levels in our phytodiverse subtropical forest ecosystem. We discuss the potential role of host specificity of dominant herbivores, which are often expected to show a high degree of specialization in many (sub)tropical forests. In the forest system we studied, a much higher impact of polyphagous species than traditionally assumed might explain the observed patterns, as these species can profit from a broad dietary mix provided by high plant diversity. Further testing is needed to experimentally verify this assumption.

Sclerophyllous oak forests are an important ecosystem type of the natural vegetation in the Mediterranean region. As a part of the mosaic-like landscape, old-growth oak forests, in particular, provide a wide range of ecosystem functions and services. However, due to the general scarcity of older forests in the Mediterranean region, studies on structure and dynamics of oak forests are mostly restricted to younger stands. The aim of this study was to analyze stand structure, dead wood, and natural regeneration of an old Quercus calliprinos forest in northern Israel (nature reserve Ya'ar Bar'am) and to compare the results with those reported from other evergreen Mediterranean oak forests. The mean density of trees was 735 ha-1, and the mean basal area amounted to 25.0 m2 ha-1. The mean tree height was 6.6 m, and the maximum tree height was 13.2 m. The mean dead wood volume was 11 m3 ha-1. The sapling density ranged from 1,050 to 6,250 ha-1. We conclude that Bar'am Forest is of great value for conservation bi...

The dominant plant species of European heathlands Calluna vulgaris is considered vulnerable to drought and enhanced nitrogen (N) loads. However, impacts may vary across the distribution range of Calluna heathlands. We tested the hypothesis that Calluna of southern and eastern marginal populations (MP) are more resistant to drought events than plants of central populations (CP), and that this is mainly due to trait differences such as biomass allocation patterns. Furthermore, we hypothesised that N fertilisation can offset differences in drought susceptibility between CP and MP. We conducted a full-factorial 2-year greenhouse experiment with Calluna plants of CP and MP and quantified growth responses in terms of biomass production, allocation and tissue δ13C signatures. Biomass production, shoot–root ratios and tissue δ13C values of 1-year-old plants were higher for CP than for MP, indicating a higher drought susceptibility of CP. These trait differences were not observed for 2-year-old plants. N fertilisation increased shoot–root ratios of 1- and 2-year-old plants and across populations due to a stimulation of the aboveground biomass allocation. As a consequence, population-related differences in drought susceptibility were offset for N-fertilised plants. We concluded that Calluna plants originating from different populations developed adaptive traits to local climates, which determined their drought sensitivity. However, the higher drought resistance of MP can be attenuated by an N-induced increase in shoot–root ratios. This suggests that analyses on plant growth responses to global change should include multi-factor approaches with a focus on different populations throughout a species’ distribution range.

The increased deposition of nutrients from the atmosphere has contributed to widespread changes in wet heathland ecosystems throughout Europe. As a result, management measures are nowadays considered a tool with which to mitigate impacts of atmospheric nutrient loads by reducing nutrient stores in the above-ground biomass and soils. A burning experiment was carried out in order to evaluate the effects of prescribed winter burning on the nutrient budgets of an extensive wet heathland complex in NW Germany (with particular reference to growth limiting N and P, but also Ca, K, and Mg). Changes in nutrient budgets were calculated by analysing the current input (atmospheric deposition), the output due to biomass combustion, and N losses due to denitrification. In the study area, atmospheric inputs amount to 3.31 g m -2 yr -1 for N, and -2 yr -1 for P. Mean N stores in the above-ground biomass are 9.34 and 9.66 g m -2 (in Calluna-Erica- and Calluna-dominated wet heaths, respectively), and biomass P contents in both vegetation types amount to 0.43 g m -2. From these stores, 47-68 % (for N) and 2-16% (for P) were removed by burning (taking into consideration the return of nutrients as a result of ash deposition). Nitrogen losses owing to denitrification range between 0.5 and 1.6 g m -2 yr -1 and may, thus, compensate for about 15-48% of the atmospheric input. However, calculations of input/output-ratios show that prescribed burning is insufficient to counterbalance present-day atmospheric nutrient loads since management cycles usually exceed a 10-year interval. Our results suggest that wet heaths managed by means of prescribed burning will accumulate nutrients, particularly N, in the long term. As a means of preserving a balanced nutrient budget on a long-term basis, high-intensity measures (e.g. high intensity mow), applied in combination with low-intensity measures, will be an indispensable instrument in wet heathland preservation.

Climate change and atmospheric deposition of nitrogen (N) affect the biodiversity patterns and functions of ecosystems world-wide. While many single-factor studies have quantified ecosystem responses to single global change drivers, less is known about the interaction effects of these drivers on ecosystem functions. Here, we present the results of a three-year field and a two-year glasshouse experiment, in which we assessed responses of Calluna vulgaris heathlands to the single and combined effects of drought events (D) and N fertilization (D: 25% precipitation reduction in the field experiment and 20-50% soil water content reduction in the glasshouse experiment; N fertilization: 35 kg N ha-1 year-1). We examined the effects of D and N treatments on growth responses of the dominant dwarf shrub Calluna vulgaris (in terms of biomass production and allocation, tissue δ13C signatures and C:N ratios) in relation to two plant life-history stages and different 'ecotypes' (sub-Atlantic vs. subcontinental heathlands). Plant responses varied strongly with life-history stage, and the interaction of N and D showed lower effects than would be expected based on additive responses to single factors. While D treatments had no effects on Calluna in the building phase (ca. ten-year-old plants), seedlings (particularly one-year-old plants) were highly susceptible to drought. Differences in response patterns were attributable to the high shoot-root ratios typical of young Calluna plants. These ratios decreased with progressing life history as a result of increasing below-ground biomass investments. Below-ground biomass production and shoot-root ratios differed between plants from the different heathland sites. Tissue δ13C signatures decreased and C:N ratios increased with plant age as a result of decreasing evaporative demands (per unit root biomass). N fertilization increases the shoot-root ratios and thereby the drought susceptibility of Calluna plants. Synthesis. Our findings suggest that plant responses to global change are difficult to anticipate by means of single-factor studies or by focusing on a single life-history stage. This highlights the need for global change research to include multiple factors and life-history stages when assessing an ecosystem's susceptibility to shifts in environmental conditions.

The diversity, spatial patterns and temporal dynamics of dead wood were examined within the near-natural beech forests (Fagus sylvatica) of Serrahn (North-eastern Germany). Data were collected in an 8 ha sample plot and in two permanent plots (0.36 and 0.25 ha) that had been established at the end of the 1960s. The mean volume of dead wood was 94 m(3) ha(-1), amounting to 14% of the total volume of all trees. The dead wood displayed a large variation in dead wood type, tree size and decay class. Standing dead wood accounted for about one-third of the total dead wood volume. The densities of standing dead trees were about 10% of the densities of the living trees over a wide range of diameters. The overall spatial distribution of dead trees exhibited a random pattern. Among the different dead wood types, standing entire dead trees and uprooted trees deviated from this pattern by displaying a significantly aggregated pattern. In the permanent plots a high mortality of overstorey trees was observed (1.3% year(-1)) and the average amount of dead wood increased greatly from 2.9 to 111.6 m(3) ha(-1) over the 35-year observation period. The near-natural beech forests of Serrahn have experienced a long period of low human interference. Nevertheless, our results suggest that the structure and dynamics of dead wood are strongly affected by the last major disturbance events that took place at the end of the Middle Ages. Information about the forest history is therefore a basic requirement when interpreting the results obtained in near-natural forests.

The effects of soil disturbance caused by the uprooting of a single or a few canopy trees on species richness and composition of vascular plant species and bryophytes were examined in a temperate beech forest (Fagus sylvatica) in northern Germany. We recorded the vegetation in 57 pairs of disturbed and adjacent undisturbed plots and established a chronosequence of mound ages to study the effect of time since microsite formation on plant species richness and composition. We found significant differences in plant species richness and composition between disturbed and adjacent undisturbed plots. Species richness of both vascular plants and bryophytes was higher in the disturbed than in the undisturbed plots, but these differences were more pronounced for bryophytes. We suggest that three main factors are responsible for this differential response. The availability of microsites on the forest floor that are suitable for the recruitment of bryophytes is lower than for vascular plants. Establishment of bryophytes in disturbed microsites is favoured by a greater abundance of propagules in the close vicinity and in the soil of the disturbed microsites, as well as by a greater variety of regeneration strategies in bryophytes than in vascular plants. Time since mound formation was a major factor determining plant species richness and composition. A significant decrease in the mean number of species was found from young mounds to intermediate and old mounds. However, differences were observed between vascular plants and bryophytes in the course of changes through time in species richness and composition. A large number of exclusive and infrequent vascular plant species was observed on young mounds, among them several disturbance specialists. We suggest that the establishment of many vascular plant species was infrequent and short-lived due to unfavourable light conditions and a low abundance of propagules. By contrast, the development of a litter layer was the main reason for the decreased mean number of bryophytes on old mounds. Our study supports the view that groups of species differing in important life history traits exhibit different responses to soil disturbance.

Heathland management is an important tool with which to modify ecosystem impacts caused by atmospheric nutrient deposition. Since changes in nutrient availability as a result of management measures affect the outcomes of heathland succession and species competition, studies on this issue are important from both a nature conservation and management point of view. This study reports the effects of prescribed burning on nutrient availability in dry heathland soils and the nutrient content of the two competing heathland species Calluna vulgaris and Deschampsia flexuosa, with particular reference to N and P. We hypothesise that winter prescribed burning leads to additional N availability, which enhances the importance of P in the context of nutrient limitation in heathland ecosystems. In the nature reserve ``Lueneburg Heath'' (NW Germany) we examined the availability of nutrients in the humus horizons and in the leachate as well as the relevant C:element ratios in Calluna and Deschampsia before and after a burning experiment. Our results show that prescribed burning resulted in drastically increased NH4+ availability in the O-horizon. We observed only short-term effects (for NO3-, PO43-, Mg) and insignificant effects on the availability of other nutrients (K, Ca). As a consequence of an increased nutrient availability in the humus horizons and a limited nutrient uptake by plants after burning, leaching increased significantly for N, Ca, K, and Mg after burning treatment. No significant changes were found in the foliar C:N ratios for either species after prescribed burning, although Deschampsia showed an increased deficiency for all the other nutrients, particularly for P, as expressed by increased foliar C:P and N:P ratios. By contrast, the nutrient content of Calluna did not change significantly, suggesting that prescribed burning favours the competitive capacity of Calluna as against Deschampsia. We assume that water shortage as a result of changes in the microclimate was mainly responsible for the deterioration of the nutrient content of Deschampsia. This gives Calluna a competitive advantage, enabling it to out-compete Deschampsia on burned heathlands, with respect to the key factor P-limitation. Heathland management is an importanttool with which to modify ecosystem impactscaused by atmospheric nutrient deposition. Sincechanges in nutrient availability as a result ofmanagement measures affect the outcomes ofheathland succession and species competition,studies on this issue are important from both anature conservation and management point ofview. This study reports the effects of prescribedburning on nutrient availability in dry heathlandsoils and the nutrient content of the two competingheathland species Calluna vulgaris andDeschampsia flexuosa, with particular referenceto N and P. We hypothesise that winter prescribedburning leads to additional N availability,which enhances the importance of P in the contextof nutrient limitation in heathland ecosystems.In the nature reserve ‘‘Lueneburg Heath’’(NW Germany) we examined the availability ofnutrients in the humus horizons and in theleachate as well as the relevant C:element ratiosin Calluna and Deschampsia before and after aburning experiment. Our results show thatprescribed burning resulted in drastically increasedNH4+ availability in the O-horizon. Weobserved only short-term effects (for NO3 – , PO43–,Mg) and insignificant effects on the availability ofother nutrients (K, Ca). As a consequence of anincreased nutrient availability in the humus horizonsand a limited nutrient uptake by plants afterburning, leaching increased significantly for N,Ca, K, and Mg after burning treatment. Nosignificant changes were found in the foliar C:Nratios for either species after prescribed burning,although Deschampsia showed an increased deficiencyfor all the other nutrients, particularly forP, as expressed by increased foliar C:P and N:Pratios. By contrast, the nutrient content of Callunadid not change significantly, suggesting that prescribedburning favours the competitive capacityof Calluna as against Deschampsia. We assumethat water shortage as a result of changes in themicroclimate was mainly responsible for thedeterioration of the nutrient content ofDeschampsia. This gives Calluna a competitiveadvantage, enabling it to out-competeDeschampsia on burned heathlands, with respectto the key factor P-limitation.

The impact of forest management on the species diversity and species composition of epiphytic bryophytes and lichens in beech forests (Fagus sylvatica ) of NE Germany was analysed. The investigations were carried out in one unmanaged and in one managed forest, with 45 sample plots of 400 m2 each. In the sample plots, the presence of the epiphytes on 2–4 randomly chosen trees (100 trees per forest) and seven environmental variables were recorded. The total number of species and the mean lichen density per mantle area was higher in the unmanaged forest than in the managed forest. Regression analyses and DCA revealed the diameter at breast height (dbh) as the most important factor affecting the species diversity and species composition in both forest types. The dbh was positively correlated with the number of growth anomalies and with the bark roughness of the phorophytes and thus a good indicator for the habitat quality. Moreover, the light conditions had a significant impact on the species composition in both forests types and on the species diversity in the managed forest. In particular, epiphytes demanding shady conditions and a consistent humidity may suffer from the abrupt exposition to radiation and the lower humidity after logging. Species typical for the unmanaged forest and most rare species must be considered as stenoecious as they demand the shady and humid conditions of the forest interior and grow on old, large trees. With the aim of sustaining the diversity of epiphytic bryophytes and lichens, forest management should ensure the continuous occurrence of big trees above the target diameter. In addition, a single tree selection felling method should be applied to minimise strong changes in the microclimate. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) Artenvielfalt und Artenzusammensetzung epiphytischer Moose und Flechten – ein Vergleich zwischen bewirtschafteten und unbewirtschafteten Buchenwaldern in Nordostdeutschland Der Einfluss der Bewirtschaftung auf die Artenvielfalt und Artenzusammensetzung epiphytischer Moose und Flechten in Buchenwaldern Nordostdeutschlands wurde analysiert. Die Untersuchungen erfolgten in einem unbewirtschafteten und einem benachbarten, bewirtschafteten Waldgebiet in jeweils 45 Untersuchungsflachen a 400 m2. In den Untersuchungsflachen wurden die Stetigkeit der Epiphyten an jeweils zwei bis vier zufallig ausgewahlten Tragerbaumen (100 Baume je Waldtyp) sowie sieben Umweltvariablen aufgenommen. Im Naturwald waren die Gesamtartenzahl sowie die mittlere Artendichte der Flechten bezogen auf die Mantelflache hoher als im Wirtschaftswald. Die Regressionsanalysen und die DCA wiesen den Brusthohendurchmesser (BHD) als den fur die Artenvielfalt und Artenzusammensetzung bedeutsamsten Faktor aus. Der BHD korrelierte positiv mit der Anzahl an Wuchsanomalien und der Rindenrauigkeit der Tragerbaume und ist deshalb ein guter Indikator fur die Habitatqualitat. Weiterhin zeigten die Lichtverhaltnisse einen signifikanten Einfluss auf die Artenzusammensetzung in beiden Waldtypen sowie auf die Artenvielfalt im Wirtschaftswald. Insbesondere schattentolerante und austrocknungsempfindliche Arten konnen durch die plotzliche Lichtstellung und Veranderung des Mikroklimas infolge forstlicher Eingriffe geschadigt werden. Die Arten mit deutlich hoherer Stetigkeit im Naturwald sowie die meisten seltenen Arten gelten als stenok, da sie die schattigen und luftfeuchten Bedingungen eines geschlossenen Waldinnenklimas benotigen und uberwiegend an alten, starken Baumen siedeln. Zur Erhaltung der Artenvielfalt epiphytischer Moose und Flechten sollten daher im Rahmen forstlichen Managements starke Baume uber den Zieldurchmesser hinaus erhalten werden. Weiterhin ist eine einzelstammweise Nutzung anzustreben, um Schwankungen im Mikroklima zu minimieren.

The endozoochorous dispersal of vascular plant species by red deer (Cervus elaphus) was investigated in three forest areas of Schleswig-Holstein and Lower Saxony. The primary aim of this study was to determine of which plant species and in what numbers diaspores are dispersed by red deer, an animal with eminently large home ranges during a single day as well as over the year. A second aim was to examine the significance of endozoochory for plant species composition and diversity in forests. Special emphasis was placed on whether there are differences between the three study sites and in the course of the vegetation period. Freshly deposited faecal pellet groups were collected in the forests on five dates between May and November 2002 and viable seed content was determined by greenhouse germination (seedling emergence method). A total of 28,009 individuals representing 59 vascular plant species were detected in 220 dung samples. Red deer appears thus as an important vector for endozoochorous dispersal of plants. The number of seedlings found in the faecal pellets differs between plant species and research areas as well as in the course of the vegetation period. Dung seed content is largely dominated by one species, Urtica dioica. Grouping the species found in dung according to their habitat preference showed that mainly species that occur in forests as well as in open vegetation and non-forest species were dispersed endozoochorously, while species occurring mainly under a closed canopy were present in the excrements only in low numbers.

Measurements of the soil pH are often used to characterize the nutritional conditions for the vegetation at a particular site, for example in ecograms describing the ecological behaviour of a (tree) species. In spite of this use and interpretation of pH measurements, certain prerequisites must be fulfilled when pH-values are to be used as an expression of the nutritional conditions for plants. Our study in deciduous forests of northern Germany shows that in strongly acid soils (pH < 4) the correlations be-tween pH-values on the one hand and S-value, base saturation and C/N-ratios on the other hand are generally low, particularly for measurements in the upper mineral horizon. By contrast, in moderately acid to neutral soils (pH 4–7), pH-values could be employed as a useful indicator of the nutritional conditions for the vegetation. The main reason for the observed discrepancy in the indicator quality of pH measurements is the presence of distinct differences in the cation exchange capacity (CEC) of the soils, which are often not taken into account when interpreting pH measurements. CEC-values close to zero may be associated with either low or comparatively high pH-values, depending on whether or not the few available cation exchange sites are occupied by protons or bases, respectively. In general, pH – S-value/base saturation/CN-ratio relationships are stronger in soil samples taken in the main (fine and coarse) root horizon than in those from the upper mineral horizon. Consequently, ecograms give a more precise description of vegetation-site relationships if the considered nutrient gradients refer to appropriate soil parameters (e.g. S-value, C/N-ratio) and to measurements in the main root horizon. Measurements of the soil pH are often used to characterize the nutritional conditions for the vegetation at a particular site, for example in ecograms describing the ecological behaviour of a (tree) species. In spite of this use and interpretation of pH measurements, certain prerequisites must be fulfilled when pH-values are to be used as an expression of the nutritional conditions for plants. Our study in deciduous forests of northern Germany shows that in strongly acid soils (pH < 4) the correlations be-tween pH-values on the one hand and S-value, base saturation and C/N-ratios on the other hand are generally low, particularly for measurements in the upper mineral horizon. By contrast, in moderately acid to neutral soils (pH 4–7), pH-values could be employed as a useful indicator of the nutritional conditions for the vegetation. The main reason for the observed discrepancy in the indicator quality of pH measurements is the presence of distinct differences in the cation exchange capacity (CEC) of the soils, which are often not taken into account when interpreting pH measurements. CEC-values close to zero may be associated with either low or comparatively high pH-values, depending on whether or not the few available cation exchange sites are occupied by protons or bases, respectively. In general, pH – S-value/base saturation/CN-ratio relationships are stronger in soil samples taken in the main (fine and coarse) root horizon than in those from the upper mineral horizon. Consequently, ecograms give a more precise description of vegetation-site relationships if the considered nutrient gradients refer to appropriate soil parameters (e.g. S-value, C/N-ratio) and to measurements in the main root horizon.

There is ample evidence that continuously existing forests and afforestations onpreviously agricultural land differ with regard to ecosystem functions and servicessuch as carbon sequestration, nutrient cycling and biodiversity. However, nostudies have so far been conducted on possible long-term (100 years) impacts on tree growth caused by differences in the ecological continuity of forest stands. In the present study we analysed the variation in tree-ring width of sessile oak (Quercus petraea (Matt.) Liebl.) trees (mean age 115–136 years) due to different land-use histories (continuously existing forests, afforestations both on arable land and on heathland). We also analysed the relation of growth patterns to soil nutrient stores and to climatic parameters (temperature, precipitation). Tree rings formed between 1896 and 2005 were widest in trees afforested on arable land. This can be attributed to higher nitrogen and phosphorous availability and indicates that former fertilisation may continue to affect the nutritional status of forest soils for more than one century after those activities have ceased. Moreover, these trees responded more strongly to environmental changes – as shown by a higher mean sensitivity of the tree-ring widths – than trees of continuously existing forests. However, the impact of climatic parameters on the variability in tree-ring width was generally small, but trees on former arable land showed the highest susceptibility to annually changing climatic conditions. We assume that incompletely developed humus horizons as well as differences in the edaphon are responsible for the more sensitive response of oak trees of recent forests (former arable land and former heathland) to variation in environmental conditions. We conclude that forests characterised by a long ecological continuity may be better adapted to globalchange than recent forest ecosystems. There is ample evidence that continuously existing forests and afforestations on previously agricultural land differ with regard to ecosystem functions and services such as carbon sequestration, nutrient cycling and biodiversity. However, no studies have so far been conducted on possible long-term (>100 years) impacts on tree growth caused by differences in the ecological continuity of forest stands. In the present study we analysed the variation in tree-ring width of sessile oak (Quercus petraea (Matt.) Liebl.) trees (mean age 115–136 years) due to different land-use histories (continuously existing forests, afforestations both on arable land and on heathland). We also analysed the relation of growth patterns to soil nutrient stores and to climatic parameters (temperature, precipitation). Tree rings formed between 1896 and 2005 were widest in trees afforested on arable land. This can be attributed to higher nitrogen and phosphorous availability and indicates that former fertilisation may continue to affect the nutritional status of forest soils for more than one century after those activities have ceased. Moreover, these trees responded more strongly to environmental changes – as shown by a higher mean sensitivity of the tree-ring widths – than trees of continuously existing forests. However, the impact of climatic parameters on the variability in tree-ring width was generally small, but trees on former arable land showed the highest susceptibility to annually changing climatic conditions. We assume that incompletely developed humus horizons as well as differences in the edaphon are responsible for the more sensitive response of oak trees of recent forests (former arable land and former heathland) to variation in environmental conditions. We conclude that forests characterised by a long ecological continuity may be better adapted to global change than recent forest ecosystems.

Future climates are likely to include extreme events, which in turn have great impacts on ecological systems. In this study, we investigated possible effects that could mitigate stem breakage caused by a rare and extreme ice storm in a Chinese subtropical forest across a gradient of forest diversity. We used Bayesian modeling to correct stem breakage for tree size and variance components analysis to quantify the influence of taxon, leaf and wood functional traits, and stand level properties on the probability of stem breakage. We show that the taxon explained four times more variance in individual stem breakage than did stand level properties; trees with higher specific leaf area (SLA) were less susceptible to breakage. However, a large part of the variation at the taxon scale remained unexplained, implying that unmeasured or undefined traits could be used to predict damage caused by ice storms. When aggregated at the plot level, functional diversity and wood density increased after the ice storm. We suggest that for the adaption of forest management to climate change, much can still be learned from looking at functional traits at the taxon level. Future climates are likely to include extreme events, which in turn have great impacts on ecological systems. In this study, we investigated possible effects that could mitigate stem breakage caused by a rare and extreme ice storm in a Chinese subtropical forest across a gradient of forest diversity. We used Bayesian modeling to correct stem breakage for tree size and variance components analysis to quantify the influence of taxon, leaf and wood functional traits, and stand level properties on the probability of stem breakage. We show that the taxon explained four times more variance in individual stem breakage than did stand level properties; trees with higher specific leaf area (SLA) were less susceptible to breakage. However, a large part of the variation at the taxon scale remained unexplained, implying that unmeasured or undefined traits could be used to predict damage caused by ice storms. When aggregated at the plot level, functional diversity and wood density increased after the ice storm. We suggest that for the adaption of forest management to climate change, much can still be learned from looking at functional traits at the taxon level. © 2014 Nadrowski et al.

We studied gradients in field layer vegetation across ecotone-type borderlines between 12 ancient woodlands and adjacent secondary deciduous woodlands on former amble land. The aim of the study was to determine how distance from the borderline influences species distributions as compared with soil factors and degree of canopy closure. Correspondence Analysis showed that distance from the borderline is closely related to the first ordination axis at all study sites. Canonical Correspondence Analysis with variation partitioning revealed that distance from the borderline was the single most important factor in explaining vegetation variation. In general, the results suggest the following order of decreasing importance: Distance from the borderline > Soil reaction > Soil nitrogen > Soil moisture > Canopy cover. However, the sum of soil variables, as estimated by weighted averages of Ellenberg indicator values for moisture, reaction and nitrogen, accounted for as much as ca. 50-70% of the total variation explained by environmental variables. Important gradients in field layer vegetation are due to a decrease in typical woodland species and an increase in other species with increasing distance from the ancient woodland. The results suggest dispersal limitation of woodland species as an important determinant of secondary forest succession. However, the importance of distance to species distributions decreases with increasing stand age as most woodland species gradually colonize the recent woodlands. After 70 yr, ca. 50 % of the woodland species present at a site showed complete colonization within 50 m from the ancient woodland border.

Migration of the herb species Anemone nemorosa from older woodlands into adjacent, recently established deciduous woodlands on former arable land was studied. The wood anemone had colonized part of all studied recent woods, varying in age between 30 and 75 years. Cover of A. nemorosa in the recent woods decreased with increasing distance from the older woodland at all sites but one, indicating dispersal limitation during colonization. The advancing edge of most populations was characterized by negative logarithmic decrease in cover with establishment of isolated pioneer individuals and later gradual infill between pioneers. Migration rates were calculated by three methods. The mean migration rate of A. nemorosa based on observed maximum cover in the recent woods was 0.20 m year1, 0.40 m year-1 based on half maximum cover and 0.85 m year1 based on the individual found farthest from the former woodland border. The calculated migration rates were consistently higher than the rate of possible rhizome growth. Seed dispersal and establishment is thus very important for colonization of new woodlands. Migration rates increased with tree canopy cover–especially cover of broad-leaved species with quickly decomposing litter–and with soil pH. Migration rates decreased with increasing grass cover in the field layer. These differences in migration rates may be due to increased micro-site availability for establishment at high canopy cover, low grass cover and high soil pH. Our results show that the wood anemone generally colonizes recent woods from nearby source populations. However, colonization proceeds relatively slowly and is limited by both seed dispersal and availability of suitable micro-sites. Gradients in abundance of A. nemorosa within secondary woods may be detectable for long periods of time and indicate the recent origin of a woodland.

1 We studied the migration of field layer plants across ecotones between ancient woodlands and recent deciduous woods on former arable land varying in age between 30 and 75 years. 2 Number and percentage cover of woodland species in recent woods decreased with increasing distance to the ancient woods, and increased with the age of the recent woods, indicating dispersal limitation during secondary succession. 3 Colonization by typical woodland plants was observed in 183 of 200 species × site combinations. In 72 combinations, a colonization front was characterized by logarithmic or linear decrease in species cover, indicating establishment of isolated individuals and gradual infill of gaps. This pattern was most common in ant-dispersed species and less frequent in species with adhesive or ingested seeds. 4 Migration rates were calculated for 49 woodland species. Mean migration rates based on maximum cover in recent woods varied from 0.00 to 1.00 m year−1 between species, with a median migration rate of 0.30 m year−1. Migration rates calculated on occurrence of the farthest individual ranged from 0.00 to 1.25 m year−1, with a median rate of 0.53 m year−1. 5 Ant-dispersed species had lower migration rates based on maximum cover compared with species with adhesive or ingested seeds. No differences between dispersal modes were found when comparing migration rates based on the farthest individuals. Most of the calculated migration rates (84%) exceeded the rate of possible vegetative spread of woodland species. 6 Establishment of a field layer vegetation in secondary woods comparable to that of the adjacent ancient stands proceeded at a rate of c. 0.3–0.5 m year−1. We conclude that scale and intensity of temperate forest management should be adjusted to the relatively slow migration of the field layer flora in order to enable complete recovery during a management cycle.

We investigated climate-growth relationships (in terms of tree-ring width, basal area increment (BAI), and tree-ring δ 13C signatures) of Quercus petraea in Central Europe (Luxembourg). Tree responses were assessed for 160 years and compared for sites with contrasting water supply (i.e. Cambisols vs. Regosols with 175 and 42 mm available water capacity, respectively). Oak trees displayed very low climate sensitivity, and climatic variables explained only 24 and 21 % of variance in tree-ring width (TRW) (Cambisol and Regosol sites, respectively). Contrary to our expectations, site-related differences in growth responses (i.e. BAI, δ 13C signatures) to climate shifts were not significant. This finding suggests a high plasticity of oak trees in the study area. Despite a distinct growth depression found for all trees in the decade 1988-1997 (attributable to increasing annual mean temperatures by 1.1 °C), oak trees completely recovered in subsequent years. This indicates a high resilience of sessile oak to climate change. Shifts in δ 13C corr signatures were mainly affected by temperature, and peaks in δ 13C corr values (corrected for the anthropogenic increase in atmospheric CO 2) coincided with decadal maximum temperatures. Correlations between δ 13C signatures and TRW (mainly affected by precipitation) were not significant. This finding suggests that wood growth often was disconnected from carbon assimilation (e.g. due to carbon storage in the trunk or allocation to seeds). Since the selection of drought-resistant tree species gains importance within the context of adaptive forest management strategies, Q. petraea proves to be an adaptive tree species in Central Europe's forests under shifting climatic conditions.

Experimental forest plantations to study biodiversity–ecosystem functioning (BEF) relationships have recently been established in different regions of the world, but subtropical biomes have not been covered so far. Here, we report about the initial survivorship of 26 tree species in the first such experiment in subtropical China. In the context of the joint Sino–German–Swiss Research Unit “BEF-China,” 271 experimental forest plots were established using 24 naturally occurring tree species and two native commercial conifers. Based on the survival inventories carried out in November 2009 and June 2010, the overall survival rate was 87 % after the first 14 months. Generalized mixed-effects models showed that survival rates of seedlings were significantly affected by species richness, the species’ leaf habit (deciduous or evergreen), species identity, planting date, and altitude. In the first survey, seedling establishment success decreased with increasing richness levels, a tendency that disappeared in the second survey after replanting. Though evergreen species performed less well than deciduous species with establishment rates of 84 versus 93 % in the second survey, their planting success exceeded the general expectation for subtropical broad-leaved evergreen species. These results have important implications for establishing mixed-species plantations for diversity conservation and improvement of ecosystem functioning in the Chinese subtropics and elsewhere. Additional costs associated with mixed-species plantations as compared to conventional plantations also demonstrate the potential of upscaling BEF experiments to large-scale afforestation projects. Experimental forest plantations to study biodiversity-ecosystem functioning (BEF) relationships have recently been established in different regions of the world, but subtropical biomes have not been covered so far. Here, we report about the initial survivorship of 26 tree species in the first such experiment in subtropical China. In the context of the joint Sino-German-Swiss Research Unit "BEF-China," 271 experimental forest plots were established using 24 naturally occurring tree species and two native commercial conifers. Based on the survival inventories carried out in November 2009 and June 2010, the overall survival rate was 87 % after the first 14 months. Generalized mixed-effects models showed that survival rates of seedlings were significantly affected by species richness, the species' leaf habit (deciduous or evergreen), species identity, planting date, and altitude. In the first survey, seedling establishment success decreased with increasing richness levels, a tendency that disappeared in the second survey after replanting. Though evergreen species performed less well than deciduous species with establishment rates of 84 versus 93 % in the second survey, their planting success exceeded the general expectation for subtropical broad-leaved evergreen species. These results have important implications for establishing mixed-species plantations for diversity conservation and improvement of ecosystem functioning in the Chinese subtropics and elsewhere. Additional costs associated with mixed-species plantations as compared to conventional plantations also demonstrate the potential of upscaling BEF experiments to large-scale afforestation projects.

Competition for canopy space is a process ofmajor importance in forest dynamics. Although virgin andold-growth European beech (Fagus sylvatica L.) forests inEurope have been studied for many years, there are to dateno studies of individual-tree crown plasticity and the waythis is influenced by local neighborhood interactions inthese forests. In this study, we analyzed crown plasticityand local neighborhood interactions of individual trees inthe upper canopy of the old-growth beech forests of Serrahn,northeast Germany. In a 2.8-ha sample plot, wemeasured crown radii of all upper canopy trees and analyzedthe direction and extent of crown asymmetry. Size,relative position, and distance of neighboring trees wereused to construct vectors of neighborhood asymmetrywithin different distances from target trees. The crowns ofbeech trees showed strong morphological plasticity. Meanabsolute and relative displacement of crown centers fromthe stem base were 1.95 m and 0.37, respectively. Circular–circular rank correlation coefficients between thedirection of crown displacement and the direction ofneighborhood pressure showed that trees strongly positionedtheir crowns away from local neighbors. Highestcorrelation coefficients were obtained when basal area andrelative position of neighboring trees within a radialdistance of 12 m were considered. Clark and Evans indexand Ripley’s K-function showed that crowns were moreregularly distributed than stems. Projected canopy coverwas about 10% higher than canopy cover with simulatedcircular crowns. We conclude that the crowns of olderbeech trees have a high ability to plastically respond tochanges in the local canopy conditions, enabling veryeffective exploitation of canopy space. Competition for canopy space is a process ofmajor importance in forest dynamics. Although virgin andold-growth European beech (Fagus sylvatica L.) forests inEurope have been studied for many years, there are to dateno studies of individual-tree crown plasticity and the waythis is influenced by local neighborhood interactions inthese forests. In this study, we analyzed crown plasticityand local neighborhood interactions of individual trees inthe upper canopy of the old-growth beech forests of Serrahn,northeast Germany. In a 2.8-ha sample plot, wemeasured crown radii of all upper canopy trees and analyzedthe direction and extent of crown asymmetry. Size,relative position, and distance of neighboring trees wereused to construct vectors of neighborhood asymmetrywithin different distances from target trees. The crowns ofbeech trees showed strong morphological plasticity. Meanabsolute and relative displacement of crown centers fromthe stem base were 1.95 m and 0.37, respectively. Circular–circular rank correlation coefficients between thedirection of crown displacement and the direction ofneighborhood pressure showed that trees strongly positionedtheir crowns away from local neighbors. Highestcorrelation coefficients were obtained when basal area andrelative position of neighboring trees within a radialdistance of 12 m were considered. Clark and Evans indexand Ripley’s K-function showed that crowns were moreregularly distributed than stems. Projected canopy coverwas about 10% higher than canopy cover with simulatedcircular crowns. We conclude that the crowns of olderbeech trees have a high ability to plastically respond tochanges in the local canopy conditions, enabling veryeffective exploitation of canopy space.

Questions: The maintenance of a diverse sapling pool is of particular importance for the regeneration and persistance of species-rich forest ecosystems. However, the mechanisms of co-existence of saplings have rarely been studied experimentally. Do species richness, species composition, species identity and stand density affect the co-existence, growth patterns and crown architecture of tree saplings? Location: Jiangxi Province, southeast China. Methods: In a field experiment, we manipulated the local neighbourhood of saplings of four early-successional subtropical species (Schima superba, Elaeocarpus decipiens, Quercus serrata and Castanea henryi) with regard to species richness (one, two and four species), species composition (monocultures, six-two-species combinations and one-four-species combination) and stand density (low, intermediate and high). We tested for treatment effects and impact of species identity on growth variables, biomass allocation, crown architectural traits and branch demography. Results: Species richness was a poor predictor of all response variables, but enhanced pruning and branch turnover. In contrast, species composition proved to be of great importance for growth, biomass allocation, crown architecture and branch demography. Local neighbourhood interactions of saplings were characterized by complementary or facilitative, as well as by competitive mechanisms. Intra-specific competition was higher than inter-specific competition for two species (C. henryi, Q. serrata) depending on the respective species combination. To a high degree, the competitive ability of species can be explained by species identity. Competition for light likely played a major role in our experiment, as evidenced by the strong response of crown architecture and branch demography to the manipulated predictor variables. Conclusions: Effects of species composition and species identity on growth rates and crown architecture variables of tree saplings point to niche separation as a mechanism of species co-existence, while effects of species richness were not yet prominent at the sapling life stage. In a field experiment, we manipulated the local neighbourhood of saplings of four species and surveyed tree sapling growth and crown architecture. Effects of species composition and species identity on growth rates and crown architectural variables point to niche separation as a mechanism of species coexistence, while effects of species richness were not yet prominent at the sapling life stage. © 2012 International Association for Vegetation Science.

In the present study we analysed whether airborne N pollution may constitute one important driver for the encroachment of Molinia caerulea in dry heathland ecosystems. Based on full-factorial field experiments (in 2006 and 2008) and complementary greenhouse experiments (in 2008), we quantified growth responses of Molinia caerulea to N and P fertilisation (50 kg N ha(-1) year(-1), 20 kg P ha(-1) year(-1)). Aboveground biomass production of Molinia caerulea was limited by P in 2006, but by N in both experiments in 2008. In the greenhouse experiment, N addition caused a sixfold increase of the biomass of vegetative tillers, and in all experiments the biomass and numbers of flowering tillers showed a significant increase due to fertilisation. Our experiments indicated that growth of Molinia caerulea was primarily limited by N, but in dry heaths the kind of nutrient limitation may be mediated by other factors such as water availability during the vegetative period. Shifts in biomass allocation patterns resulting from N fertilisation showed that Molinia caerulea encroachment in dry heaths is not only attributable to increased leaf biomass, but also due to higher investments in reproductive tissue that allow for increased seed production and thus accelerated encroachment of seedlings in places where the dwarf shrub canopy has been opened after disturbance.

In this study we examine the relationships between the vegetation of beech and beech-oak forest communities (Hordelymo-Fagetum, Galio-Fagetum, Deschampsio-Fagetum, Betulo-Quercetum) and their soil conditions in the lowlands of northern Germany, based on 84 sample plots. In all plots the vegetation was recorded and soil parameters were analysed (thickness of the O- and the A-horizons, pH, S-value, base saturation, C/N, mean Ellenberg moisture indicator value). The vegetation classification according to the traditional Braun-Blanquet approach was compared with the result of a multivariate cluster analysis. Vegetation-site relationships were analysed by means of an indirect gradient analysis (DCA). Both traditional classification methods and the cluster analysis have produced comparable classification results. So far as the species composition is concerned, a similar grouping of sample plots was found in both approaches. Multivariate cluster analysis thus supports the classification found by the Braun-Blanquet method. The result of the DCA shows that the four forest communities mentioned above represent clearly definable ecological units. The main site factor influencing changes in the species composition is a base gradient, which is best expressed by the S-value. In addition, within the series Hordelymo-Fagetum - Galio-Fagetum - Deschampsio-Fagetum the C/N-ratios and the thickness of the organic layers (O-horizon) increase continuously. By contrast, the floristic differences between oligotrophic forest communities (i.e., Deschampsio-Fagetum and Betulo-Quercetum) cannot be explained by a base gradient and increasing C/N-ratios. It is suggested that a different forest management history in some cases (e.g., promotion of Quercus robur by silvicultural treatments) is responsible for differences in the species composition, but on the other hand the result of the DCA indicates that Fagus sylvatica is replaced by Quercus robur with increasing soil moisture (i.e., with the increasing influence of a high groundwater table). Summarizing these results, it can be concluded that the ecological importance of single site factors affecting the species composition changes within the entire site spectrum covered by the beech and beech-oak forests of northern Germany.

The endozoochorous and epizoochorous dispersal of vascular plant species by roe deer (Capreolus capreolus) and wild boar (Sus scrofa) was investigated in forest areas of Schleswig-Holstein and Lower Saxony, Germany. The primary aim of this study was to learn about which plant species and in what numbers diaspores are dispersed by the two wild ungulate species. In particular, the significance of zoochory for species composition and biodiversity of forests was evaluated. Fresh faecal pellets were collected from April-November 2001 in the forests of the two study areas. In addition, the coats and hooves of shot roe deer and wild boar were brushed out. The number of viable seeds was determined by greenhouse germination (seedling emergence method). The samples were spread in trays over sterilized soil from the study forests and were kept under controlled conditions in the greenhouse for 12 months. A total of 2,473 individuals from 77 vascular plant species were recorded. While roe deer exceeded wild boar concerning seed contents in the faeces, the significance of roe deer for epizoochorous dispersal was relatively low compared with wild boar. An analysis of the habitat preference of the vascular plant species dispersed by the two ungulate species revealed a high proportion of species growing in forests as well as in the open landscape, and also of non-forest species, while woody plants and herbaceous species closely tied to forest habitats were severely underrepresented. We also discuss consequences for forest ecology and nature conservation.