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Forest productivity is a crucial integrator of ecosystem functions and services. Although the effects of landscape structure on species richness and stand structure have been extensively studied, how landscape structures affect forest productivity and their interactions with stand‐level attributes, especially in the context of considerable land use change, remain unclear. In this study, we investigated the effects of landscape structures (fragmentation, complexity, and heterogeneity) and their interactions with stand‐level attributes on forest productivity in the conterminous United States across three spatial scales (1–3 km), using an extensive forest inventory dataset from the national forest inventories (NFI) plots. Our results revealed that all landscape indices around selected forest plots significantly increased from 2006 to 2016. Across three scales, forest productivity and stand‐level attributes (number of trees, tree species richness, and structural diversity) exhibited unimodal relationships with landscape fragmentation and complexity, while generally showed positive correlations with landscape heterogeneity. The interactions between landscape structures and stand attributes enhanced the explanatory power of forest productivity. Landscape complexity directly or indirectly reduced forest productivity by decreasing the number of trees and tree species richness, whereas landscape fragmentation and heterogeneity had the opposite effects. Furthermore, landscape heterogeneity and stand age had relatively stronger total effects (the sum of direct and indirect effects) on forest productivity, and their strength increased modestly with spatial scales. However, tree species richness consistently had the lowest total effects. Our study elucidates the complex driving mechanisms of landscape patterns on forest productivity across spatial scales, providing a deeper understanding of ecosystem complexity and responses to accelerating land use changes. [ABSTRACT FROM AUTHOR]

Summary: Decades of studies have demonstrated links between biodiversity and ecosystem functioning, yet the generality of the relationships and the underlying mechanisms remain unclear, especially for forest ecosystems.Using 11 tree‐diversity experiments, we tested tree species richness–community productivity relationships and the role of arbuscular (AM) or ectomycorrhizal (ECM) fungal‐associated tree species in these relationships.Tree species richness had a positive effect on community productivity across experiments, modified by the diversity of tree mycorrhizal associations. In communities with both AM and ECM trees, species richness showed positive effects on community productivity, which could have resulted from complementarity between AM and ECM trees. Moreover, both AM and ECM trees were more productive in mixed communities with both AM and ECM trees than in communities assembled by their own mycorrhizal type of trees. In communities containing only ECM trees, species richness had a significant positive effect on productivity, whereas species richness did not show any significant effects on productivity in communities containing only AM trees.Our study provides novel explanations for variations in diversity–productivity relationships by suggesting that tree–mycorrhiza interactions can shape productivity in mixed‐species forest ecosystems. [ABSTRACT FROM AUTHOR]

The current study assessed the association of eucalyptus-tree spacing with forest growth and yield, as well as with the floristic composition, diversity and yield of natural grassland grown in silvopastoral systems in Pampa biome. Data were collected in six family cattle-ranching area in Bagé County (RS). The effect of two different genetic materials (seminal-origin Eucalyptus dunnii plant and one Eucalyptus grandis clone) on shading features of plants grown in 3 planting-spacing dimensions (625, 312 and 208 trees ha-1) was assessed, as well as their association with herbaceous extract (bare soil; green cover; forage dry matter; floristic composition; species richness; and grass, legumes and winter - and summer-growth species rates) and forestry (litter accumulation, diameter at breast height, total height and volume per hectare) variables. Planting carried out at the highest tree density (625 trees ha-1) has increased forest yield. However, it reduced green cover, herbaceous extract dry-matter yield and species richness, mainly in grasses and legumes with greater forage potential. Conversely, it is possible combining forestry and animal yield to the preservation of native forage species at low tree densities (204 to 312 trees ha-1). [ABSTRACT FROM AUTHOR]

Reclamation of disturbances from oil sands mining requires effective soil management to ensure successful plant establishment and to promote recovery of native plant communities. In this study we investigated the effects of salvage depths (shallow vs. deep) and placement depths (shallow vs. deep) of forest topsoil on plant establishment, species richness, and soil properties in two substrate types (sand and peat-mineral). Shallow salvage led to greater tree stem densities and higher canopy cover for most plant groups, although there was no significant difference in species richness between shallow and deep salvages. Deep placement generally resulted in greater canopy cover, while its effect on plant density was very small for most plant groups. On peat-mineral substrate, fewer differences were detected between shallow and deep salvage, and multiple treatments resulted in greater cover. Findings suggest that a balance between maximizing the area over which propagules are redistributed and providing sufficient resources for successful plant establishment is necessary. Forest topsoil from shallow salvages and deep placements is recommended when targeting increased site productivity and species diversity. In contrast, deep salvage should be used when the primary objective is to obtain maximum reclamation material volume. Salvage depth effects may be influenced by substrate type, with peat-mineral substrate providing more favourable conditions for plant establishment. Further research is needed to assess the long-term impacts of different salvage and placement depths on plant community development and the potential effects of substrate properties on soil and plant response. [ABSTRACT FROM AUTHOR]

Understanding the biodiversity–productivity relationship (BPR) is crucial for biodiversity conservation and ecosystem management. While it is known that diversity enhances forest productivity, the underlying mechanisms at the local neighborhood level remain poorly understood. We established a 9.6 ha dynamic forest plot to study how neighborhood diversity, intraspecific competition, and interspecific competition influence tree growth across spatial scales using linear mixed-effects models. Our analysis reveals a significant positive correlation between neighborhood species richness (NSR) and relative growth rate (RGR). Notably, intraspecific competition, measured by conspecific neighborhood density and resource competition, negatively impacts RGR at finer scales, indicating intense competition among conspecifics for limited resources. In contrast, interspecific competition, measured by heterospecific density and resource competition, has a negligible impact on RGR. The relative importance of diversity and intra/interspecific competition in influencing tree growth varies with scale. At fine scales, intraspecific competition dominates negatively, while at larger scales, the positive effect of NSR on RGR increases, contributing to a positive BPR. These findings highlight the intricate interplay between local interactions and spatial scale in modulating tree growth, emphasizing the importance of considering biotic interactions and spatial variability in studying BPR. [ABSTRACT FROM AUTHOR]

A long-standing key issue for examining the relationships between biodiversity and ecosystem functioning (BEF), such as forest productivity, is whether ecosystem functions are influenced by the total number of species or the properties of a few key species. Compared with controlled ecosystem experiments, the BEF relationships in secondary forest remain unclear, as do the effects of common species richness and rare species richness on the variation in ecosystem functions. To address this issue, we conducted field surveys at five sampling sites (1 ha each) with subtropical secondary evergreen broad-leaved forest vegetation. We found (1) a positive correlation between species richness and standing aboveground biomass (AGB); (2) that common species were primarily responsible for the distribution patterns of species abundance and dominance; although they accounted for approximately 25% of the total species richness on average, they represented 86–91% of species abundance and 88–97% of species dominance; and (3) that common species richness could explain much more of the variation in AGB than total species richness (common species plus rare species) at both the site and plot scales. Because rare species and common species were not equivalent in their ability to predict productivity in the biodiversity-ecosystem productivity model, redundant information should be eliminated to obtain more accurate results. Our study suggested that woody plant species richness and productivity relationship in subtropical forest ecosystem can be explained and predicted by a few common species. [ABSTRACT FROM AUTHOR]

Examining the changes in woody plant structural diversity along an inverse elevation-dependent warming gradient will enhance our mechanistic understanding of how warming affects forest communities because such an inverse elevational gradient reflects a warming trend in a mountain landscape. Here, we investigated the effects of warming on the patterns of species composition and structural diversity in a subtropical broadleaved forest. We calculated a warming index based on elevational difference and modeled the aspect-related potential incident radiation (PDIR) using nonparametric multiplicative regression. We tested the changes in structural diversity of three communities for significant differences along the warming gradient. We associated both the warming index and PDIR with the principal components and tested their relationships for significant differences. We found that trees of different sizes varied in their response to the warming gradient. While a significant decreasing trend was exhibited in both species diversity and size diversity for trees of all sizes and for adult trees along the warming gradient, no significant changes in seedlings were found, and the average basal area value was the highest for the warmest community. Our findings demonstrated that a short-range elevational gradient was adequate to separate the communities in species composition and structural diversity. Patterns of structural diversity along the warming gradient varied in size classes. The community at a higher elevation had more indicator species that were unique in separating the community from others. Principal component analysis showed that the first two principal components were negatively correlated with the warming index, indicating that warming destabilized species composition and community structure. Our study suggests that warming is the major driver of changes in structural diversity and species composition of woody plant communities in a subtropical broadleaved forest and that warming may promote tree productivity at the community level but reduce structural diversity at the quadrat level. [ABSTRACT FROM AUTHOR]

Forest productivity (FP) depends not only on tree species diversity but also on functional traits, stand structure, and environmental factors; however, causation and relative importance remain controversial. The effects of tree species diversity (species richness), trait community-weighted mean (CWM), forest structure (forest density and maximum DBH), and environmental factors (soil nutrients and elevation) on larch (Larix principis-rupprechtii Mayr) forests' productivity were investigated, and the relative importance of each factor in determining productivity was quantified. Our results showed that stand structure and functional traits had significant positive effects on the basal area increment (BAI) of larch stands (p < 0.05) and were more important than tree diversity and environmental factors in explaining BAI variations. The contribution ratio of each influencing factor was as follows: stand structure (59%), functional composition (30%), environmental factors (9%), and species diversity (SD) (2%). The biomass ratio hypothesis was more important than the niche complementarity hypothesis in explaining the relationship between species diversity and productivity. The structural equation model showed that environmental factors did not directly affect the BAI in larch forests but indirectly affected the BAI through tree diversity and stand structure. Therefore, in larch forests with low species richness, it is more important to adjust stand structure to maintain overyielding while also considering the influence of environmental factors. [ABSTRACT FROM AUTHOR]

The relationship between primary productivity and diversity has been demonstrated across taxa and spatial scales, but for organisms with biphasic life cycles, little research has examined whether productivity of larval and adult environments influence each life stage independently, or whether productivity of one life stage's environment outweighs the influence of the other. Experimental work demonstrates that tadpoles of stream-breeding anurans can exhibit a top-down influence on aquatic primary productivity (APP), but few studies have sought evidence of a bottom-up influence of primary productivity on anuran abundance, species richness and community composition, as seen in other organisms. We examined aquatic and terrestrial primary productivity in two forest types in Borneo, along with amphibian abundance, species richness, and community composition at larval and adult stages, to determine whether there is evidence for a bottom-up influence of APP on tadpole abundance and species richness across streams, and the relative importance of aquatic and terrestrial primary productivity on larval and adult phases of anurans. We predicted that adult richness, abundance, and community composition would be influenced by terrestrial primary productivity, but that tadpole richness, abundance, and community composition would be influenced by APP. Contrary to expectations, we did not find evidence that primary productivity, or variation thereof, predicts anuran richness at larval or adult stages. Further, no measure of primary productivity or its variation was a significant predictor of adult abundance, or of adult or tadpole community composition. For tadpoles, we found that in areas with low terrestrial primary productivity, abundance was positively related to APP, but in areas with high terrestrial primary productivity, abundance was negatively related to APP, suggesting a bottom-up influence of primary productivity on abundance in secondary forest, and a top-down influence of tadpoles on primary productivity in primary forest. Additional data are needed to better understand the ecological interactions between terrestrial primary productivity, aquatic primary productivity, and tadpole abundance. [ABSTRACT FROM AUTHOR]

Background: The Rio de la Plata grassland region is dominated by temperate grasslands, with the scarce natural forests, influenced floristically by adjacent biogeographical provinces. Uruguay represents the southern limit for many tree species of the Paranaense Province, several of which inhabit the hillside forests. With many species shifting poleward due to climate change, we do not yet know how current environmental factors, particularly climatic ones, are linked to the tree diversity of this flora nowadays. The aim of this study is to understand the geographic pattern of tree richness in the hillside forests of Uruguay, evaluating the water–energy and the environmental heterogeneity hypotheses. The distribution of the hillside forest trees was obtained by compiling and updating the herbaria database and distribution maps of woody plants of Uruguay. The presence/absence of each species, and then the species richness, were georeferenced over a grid that covers Uruguay with 302 cells (660 km2). Over the same grid were compiled environmental variables associated with climate and environmental heterogeneity. The relationship between richness and environmental variables was studied by applying general linear models (GLM). As a strong autocorrelation was detected, a residuals auto-covariate term was incorporated into the GLM, to take into account the species richness spatial structure. Results: The tree flora of the hillside forest was composed mainly by Paranaense species that show a latitudinal gradient, with two high richness cores, in the east and northeast of Uruguay. The final model including the environmental variables and the spatial term explained 84% of the variability of tree richness. Species richness showed a positive relationship with precipitation, forest cover, potential evapotranspiration and productivity, while a negative effect of temperature variation was found. The spatial component was the primary predictor, accounting for a 30% of spatial pattern of tree richness. Conclusions: This study accounts for a large proportion of the environmental and spatial variations of the tree richness pattern of the Paranense flora in its southernmost portion. It brings support to both water–energy and environmental heterogeneity hypotheses, emphasizing the role of climate and its variation and the habitat availability on the hillside forest diversity. [ABSTRACT FROM AUTHOR]

Natural regeneration after mining activities depends largely on the soil seed bank (SSB) and aboveground vegetation (AGV) richness and composition. We evaluated the species diversity pattern of the SSB and AGV on soil and technosol across second‐growth Atlantic Forests (SGFs) after mining tailings deposition in Mariana, southeastern Brazil. Two second‐growth Atlantic seasonal semideciduous forests of different stand ages were selected: a 3‐year‐old stand of SGF re‐growing on tailings (SGF tailings) and a 30‐year‐old stand of native reference forest not affected by tailings (SGF nontailings). Overall, the results showed significant differences in forest attributes (species richness and composition) in the SSB and AGV between the two forest patches evaluated (SGF tailings and SGF nontailings). Moreover, both nonzoochoric and zoochoric dispersed species of AGV showed significant differences between second‐growth forests, with higher variability of community‐weighted mean in SGF tailings. The result shows smaller differences in species richness between forest types for both SBB (ranging 85 and 90 species) and AGV (~55 species). Despite the time difference between the secondary forest and the absence of zoochoric species in the tailings seed bank, the AGV that are re‐growing on mining tailings presented a high proportion of zoochoric species. This pattern of species richness and community composition variability observed in the technosol seed bank, and AGV that are re‐growing after the deposition of mining tailings are important recovery indicators for plant communities affected. [ABSTRACT FROM AUTHOR]

Understanding the relationship between biodiversity and productivity can be advanced by improving metrics used to quantify biodiversity. Structural diversity, that is, variation of size and form of plant organs, is an emerging biodiversity metric. However, compared with the other biodiversity metrics, its relative importance in specific components of forest productivity, for example, recruitment of new individuals, biomass net change after accounting for mortality, is largely unknown, particularly across a large spatial scale with multiple influential gradients. To address the knowledge gap, we used USDA Forest Service Forest Inventory and Analysis (FIA) data across the southcentral USA from 2008 to 2017. We calculated forest biomass increments due to recruitment and growth and net change in biomass. Then, we quantified the effects of a range of abiotic and biotic variables on the biomass increments and net change. Our results showed that (1) Structural diversity was negatively associated with the two biomass increments and net change in biomass. The negative effects were supported by increased occurrences of insects and diseases with greater structural diversity. (2) Compared with species and functional diversity, structural diversity showed a better association with biomass increments and net change, suggested by its larger absolute values of standardized coefficients, and the effects of structural diversity were negative in contrast to species diversity. (3) The effects of structural diversity, stand age, and elevation differed between natural and planted forests that may stem from the differences in stand development and species composition between the two forest types. Together, structural diversity may represent an important dimension of biodiversity impacts on plant productivity, which could be related to the exacerbated disturbances with greater structural diversity. [ABSTRACT FROM AUTHOR]

Rapid biodiversity losses under global climate change threaten forest ecosystem functions. However, our understanding of the patterns and drivers of multiple ecosystem functions across biodiversity gradients remains equivocal. To address this important knowledge gap, we measured simultaneous responses of multiple ecosystem functions (nutrient cycling, soil carbon stocks, organic matter decomposition, plant productivity) to a tree species richness gradient of 1, 4, 8, 16, and 32 species in a young subtropical forest. We found that tree species richness had negligible effects on nutrient cycling, organic matter decomposition, and plant productivity, but soil carbon stocks and ecosystem multifunctionality significantly increased with tree species richness. Linear mixed‐effect models showed that soil organisms, particularly arbuscular mycorrhizal fungi (AMF) and soil nematodes, elicited the greatest relative effects on ecosystem multifunctionality. Structural equation models revealed indirect effects of tree species richness on ecosystem multifunctionality mediated by trophic interactions in soil micro‐food webs. Specifically, we found a significant negative effect of gram‐positive bacteria on soil nematode abundance (a top‐down effect), and a significant positive effect of AMF biomass on soil nematode abundance (a bottom‐up effect). Overall, our study emphasizes the significance of a multitrophic perspective in elucidating biodiversity‐multifunctionality relationships and highlights the conservation of functioning soil micro‐food webs to maintain multiple ecosystem functions. [ABSTRACT FROM AUTHOR]

Background: Declines in plant biodiversity often have negative consequences for plant community productivity, and it becomes increasingly acknowledged that this may be driven by shifts in soil microbial communities. So far, the role of fungal communities in driving tree diversity-productivity relationships has been well assessed in forests. However, the role of bacteria and archaea, which are also highly abundant in forest soils and perform pivotal ecosystem functions, has been less investigated in this context. Here, we investigated how tree and shrub richness affects stand-level tree productivity by regulating bacterial and archaeal community diversity and composition. We used a landscape-scale, subtropical tree biodiversity experiment (BEF-China) where tree (1, 2, or 4 species) and shrub richness (0, 2, 4, 8 species) were modified. Results: Our findings indicated a noteworthy decline in soil bacterial α-diversity as tree species richness increased from monoculture to 2- and 4- tree species mixtures, but a significant increase in archaeal α-diversity. Additionally, we observed that the impact of shrub species richness on microbial α-diversity was largely dependent on the level of tree species richness. The increase in tree species richness greatly reduced the variability in bacterial community composition and the complexity of co-occurrence network, but this effect was marginal for archaea. Both tree and shrub species richness increased the stand-level tree productivity by regulating the diversity and composition of bacterial community and archaeal diversity, with the effects being mediated via increases in soil C:N ratios. Conclusions: Our findings provide insight into the importance of bacterial and archaeal communities in driving the relationship between plant diversity and productivity in subtropical forests and highlight the necessity for a better understanding of prokaryotic communities in forest soils. -4HQdD_EuWHa-cff1NJXs2 Video Abstract [ABSTRACT FROM AUTHOR]

Summary: Forest floor accumulation is a key process that influences ecosystem carbon cycling. Despite evidence suggesting that tree diversity and soil carbon are positively correlated, most soil carbon studies typically omit the response of the forest floor carbon to tree diversity loss.Here, we evaluated how tree species richness affects forest floor mass and how this effect is mediated by litterfall production and forest floor decay rate in a tree diversity experiment in a subtropical forest.We observed that greater tree species richness leads to higher forest floor accumulation at the soil surface through increasing litterfall production – positively linked to functional trait identity (i.e. community‐weighted mean functional trait) rather than functional diversity – and unchanged forest floor decay. Interestingly, structural equation modelling revealed that this lack of overall significant tree species richness effect on forest floor decay rate was due to two indirect and opposite effects cancelling each other out. Indeed, tree species richness increased forest floor decay rate through increasing litterfall production while decreasing forest floor decay rate by increasing litter species richness.Our reports of greater organic matter accumulation in the forest floor in species‐rich forests suggest that tree diversity may have long‐term and important effect on ecosystem carbon cycling and services. [ABSTRACT FROM AUTHOR]

The spatial structure of forest stands significantly influences inter-tree competition and the overall stability of the stand's ecological dynamics, and a profound understanding of forest stand spatial structure is essential for both effective forest management and ecological research. Previous studies on spatial structure have primarily employed single variables, offering only one-dimensional structural insights and lacking the capacity to interpret multidimensional information. In light of these limitations, our study introduces a novel approach founded on a six-variable distribution, aimed at conducting a comprehensive analysis and interpretation of the spatial attributes of forest stands. Diverging from conventional univariate or bivariate methods, the hexi-variate approach simultaneously considers six variables, facilitating a more intricate exploration of the intricate interrelationships within forest ecosystems from six distinct dimensions. We conducted an in-depth analysis of the spatial structural attributes within the forest stand, encompassing factors such as species diversity, size variation, spatial distribution patterns, openness, vertical stratification, and stand competition. To capture a comprehensive view of the trees' spatial information, we employed the hexadecimal distribution method, effectively quantifying their characteristics across six dimensions. Our study unveiled a significant correlation between spatial structure and stand growth, establishing a connection by integrating the spatial structure with key structural features relevant to tree size. The outcomes of this study shed light on the effectiveness and superiority of the six-element distribution method when it comes to the analysis of forest structural characteristics. Our approach offers valuable insights into the optimization of forest management strategies, encompassing selective harvesting and biodiversity conservation, thereby establishing a solid footing for sustainable forest management practices. [ABSTRACT FROM AUTHOR]

Recent long‐term tree biodiversity experiments have shown that diversity effects on productivity tend to strengthen over time, as complementarity among constituent species increases over the course of forest development. However, these community‐level metrics only account for the net outcome of multiple interactions among species and, thus, do not inform about the individual species' responses to diversity.In this study, using 11 years of growth records from a large diversity experiment, we explored how species respond to diversity based on their functional traits and those of their heterospecific neighbours over time and analysed their contribution to the community‐level overyielding.We show species‐specific responses to diversity, with fast‐growing deciduous species rapidly performing better in mixtures relative to monocultures, than slow‐growing evergreen species. Moreover, we find that species productivity in mixtures enhances over time as the proportion of slow‐growing evergreen species in the heterospecific neighbourhood increases. These patterns of response of species scale up and explain community overyielding, which occurs primarily in deciduous‐evergreen mixtures and is explained by the overyielding of deciduous species overcompensating the poor performance of evergreen species.This study sheds light on the temporal dynamics of species responses to diversity, which together help improve our understanding of community‐level overyielding over the course of stand development. Read the free Plain Language Summary for this article on the Journal blog. [ABSTRACT FROM AUTHOR]

Key message: We found that the stabilizing mechanisms for forest productivity varied across harvesting intensities in a mixed broad-leaved Korean pine forest. Effects of overyielding at high species richness and species asynchrony occurred only in unharvested and lightly harvested plots, whereas asymmetries between individuals of different size contributed significantly to stabilizing productivity when harvestings became intensive. Context: Understanding the driving factors of forest ecosystem stability has become increasingly crucial in forest management. However, it remains unclear whether and how the stabilizing mechanisms of forest productivity might be influenced by management practices. Aims: We related the temporal stability of aboveground biomass productivity to harvesting history. We further tested how three key driving mechanisms of stability might be modulated by selective harvesting intensities. Methods: Based on a 10-year monitoring (five repeated tree inventories) of a mixed broad-leaved Korean pine forest in Northeastern China recovering from selective harvesting, we examined the relative importance of two diversity-dependent mechanisms (overyielding and species asynchrony) and one size-dependent mechanism (asymmetric growth) for productivity stability across a wide range of intensities (0–73.4% basal area removed). Results: We found that selective harvesting significantly lowered the productivity stability, species asynchrony, and growth dominance coefficient. Growth dominance coefficient had an overall stronger effect on stability than species richness and asynchrony. Moreover, the strengths of stabilizing mechanisms varied across harvesting intensities: effects of overyielding at high species richness and species asynchrony were detected only in unharvested and lightly harvested plots, whereas the explanatory power of growth dominance coefficient outweighed the diversity-related variables when harvesting became intensive. Conclusions: We emphasized the importance to consider both diversity- and size-related explanatory variables as potential mechanisms for the temporal stability of forest productivity. In fact, how growth is partitioned among trees of different species as well as sizes may co-determine the response of forest stability to disturbances. [ABSTRACT FROM AUTHOR]

Birds are useful indicators of overall biodiversity, which continues to decline globally, despite targets to reduce its loss. The aim of this paper is to understand the importance of different spatial drivers for modelling bird distributions. Specifically, it assesses the importance of satellite‐derived measures of habitat productivity, heterogeneity and landscape structure for modelling bird diversity across Great Britain. Random forest (RF) regression is used to assess the extent to which a combination of satellite‐derived covariates explain woodland and farmland bird diversity and richness. Feature contribution analysis is then applied to assess the relationships between the response variable and the covariates in the final RF models. We show that much of the variation in farmland and woodland bird distributions is explained (R2 0.64–0.77) using monthly habitat‐specific productivity values and landscape structure (FRAGSTATS) metrics. The analysis highlights important spatial drivers of bird species richness and diversity, including high productivity grassland during spring for farmland birds and woodland patch edge length for woodland birds. The feature contribution provides insight into the form of the relationship between the spatial drivers and bird richness and diversity, including when a particular spatial driver affects bird richness positively or negatively. For example, for woodland bird diversity, the May 80th percentile Normalized Difference Vegetation Index (NDVI) for broadleaved woodland has a strong positive effect on bird richness when NDVI is >0.7 and a strong negative effect below. If relationships such as these are stable over time, they offer a useful analytical tool for understanding and comparing the influence of different spatial drivers. [ABSTRACT FROM AUTHOR]

1. Biodiversity is an important component of natural ecosystems, with higher species richness often correlating with an increase in ecosystem productivity. Yet, this relationship varies substantially across environments, typically becoming less pronounced at high levels of species richness. However, species richness alone cannot reflect all important properties of a community, including community evenness, which may mediate the relationship between biodiversity and productivity. If the evenness of a community correlates negatively with richness across forests globally, then a greater number of species may not always increase overall diversity and productivity of the system. Theoretical work and local empirical studies have shown that the effect of evenness on ecosystem functioning may be especially strong at high richness levels, yet the consistency of this remains untested at a global scale. 2. Here, we used a dataset of forests from across the globe, which includes composition, biomass accumulation and net primary productivity, to explore whether productivity correlates with community evenness and richness in a way that evenness appears to buffer the effect of richness. Specifically, we evaluated whether low levels of evenness in speciose communities correlate with the attenuation of the richness–productivity relationship. 3. We found that tree species richness and evenness are negatively correlated across forests globally, with highly speciose forests typically comprising a few dominant and many rare species. Furthermore, we found that the correlation between diversity and productivity changes with evenness: at low richness, uneven communities are more productive, while at high richness, even communities are more productive. 4. Synthesis. Collectively, these results demonstrate that evenness is an integral component of the relationship between biodiversity and productivity, and that the attenuating effect of richness on forest productivity might be partly explained by low evenness in speciose communities. Productivity generally increases with species richness, until reduced evenness limits the overall increases in community diversity. Our research suggests that evenness is a fundamental component of biodiversity–ecosystem function relationships, and is of critical importance for guiding conservation and sustainable ecosystem management decisions. [ABSTRACT FROM AUTHOR]

We examined the relationship between primary productivity and diversity for grassland, meadow, and savanna (GMS) vegetation in northeastern Pennsylvania, USA, where the landscape is primarily forests, agriculture, and urban or suburban development. We surveyed primary productivity, plant species diversity, invertebrate order diversity, and avian abundance and species diversity for 14 grasslands and open areas that were actively managed and three that apparently occurred naturally. Four grasslands were dominated by warm‐season grasses with the C4 photosynthetic pathway, nine were dominated by C3 grasses, forbs, and shrubs, and four had a mixture of both types. We found hump‐shaped relationships for plant species richness and bird species richness as a function of productivity but not for invertebrate order richness. Richness of invertebrates and birds increased linearly with the number sampled at each site. The number of plant species declined with increasing proportion of warm‐season grasses, as did the number of invertebrate orders collected in sweep samples, avian abundance, and avian species richness. Multiple regression showed that both landscape and vegetative characteristics influenced the bird community. Bird species richness increased with the area of the sites, the ratio of area to edge, and the distance to the nearest open area. There was no evidence for the influence of the relative abundance of native plant species on bird or invertebrate richness. GMS restoration of farmlands and mine lands with plantings of warm‐season grasses, while possibly beneficial for some forms of wildlife, seems to be less effective in maintaining the diversity of invertebrates and birds than a mixture of warm‐season grasses, cool‐season grasses, forbs, and shrubs. [ABSTRACT FROM AUTHOR]

The stability of forest productivity can reflect the functioning of forest ecosystems. It is a crucial topic to understand the relationship between biodiversity and ecosystem functions in ecology. Although previous studies have made great progress in understanding the effects of diversity, species asynchrony, and other factors on community biomass and productivity, few studies have explored how these factors affect the temporal stability of productivity. In this study, we hypothesized that diversity, species asynchrony, and topography would directly or indirectly impact the temporal stability of productivity. To test this hypothesis, we used a multiple regression model and a piecewise structural equation model based on the inventory data over 20 years (5‐year intervals) from 1992 to 2012 at Jingouling Forest Farm in Northeast China. Our results showed that species asynchrony was the main driving factor affecting the temporal stability of productivity. Structural diversity significantly decreased community stability, while species diversity had a nonsignificant effect on it. We found the combination of a multiple regression model and a piecewise structural equation model is an effective method for evaluating the factors that influence community stability. The effect of species asynchrony is crucial for understanding the ecological mechanisms underlying the diversity–stability relationship in mixed forests. [ABSTRACT FROM AUTHOR]

Forest stand structure (the characteristics and interrelationships of live trees) and site conditions (the physical and environmental characteristics of a specific location) have been linked to forest regeneration, nutrient cycling, wildlife habitat, and climate regulation. While the effects of stand structure (i.e., spatial and non-spatial) and site conditions on the single function of Cunninghamia lanceolata and Phoebe bournei (CLPB) mixed forest have been studied in previous studies, the relative importance of stand structure and site conditions in terms of productivity, species diversity, and carbon sequestration remains unresolved. In this study, a structural equation model (SEM) was adopted to analyze the relative importance of stand structure and site conditions for the forest productivity, species diversity, and carbon sequestration of CLPB mixed forest in Jindong Forestry in Hunan Province. Our research demonstrates that site conditions have a greater influence on forest functions than stand structure, and that non-spatial structures have a greater overall impact on forest functions than spatial structures. Specifically, the intensity of the influence of site conditions and non-spatial structure on functions is greatest for productivity, followed by carbon sequestration and species diversity. In contrast, the intensity of the influence of spatial structure on functions is greatest for carbon sequestration, followed by species diversity and productivity. These findings provide valuable insights for the management of CLPB mixed forest in Jindong Forestry and have significant reference value for the close-to-natural forest management (CTNFM) of pure Cunninghamia lanceolata forests. [ABSTRACT FROM AUTHOR]

Vascular epiphytes contribute substantially to floral diversity, species richness, productivity, nutrient storage and complex arboreal communities in forest ecosystems. However, they have received insufficient attention due to accessibility limitations. In this communication, we analysed the vascular epiphytic species richness and composition in sub-tropical forests (from 400 to 1300 m) of Darjeeling eastern Himalaya. The study area was classified into three elevations (low, mid and high). We studied the correlation between vascular epiphytic richness and host tree traits such as circumference at breast height (CBH), bark texture and bark pH. Additionally, we applied Canonical Correspondence Analysis (CCA) to explain epiphyte diversity with respect to climatic variables (mean annual temperature, mean annual precipitation and mean annual relative humidity). In total, 942 individuals of vascular epiphytes belonging to 71 species under 46 genera and 21 families were recorded. Orchidaceae was by far the most species-rich family followed by the fern family Polypodiaceae. The results showed the species richness in mid elevations was comparatively lower than in the low and high elevations. Our study suggests that climatic variables and host tree traits such as CBH and bark texture were closely associated with epiphytic richness and diversity. These findings could be seminal in understanding the distribution pattern of vascular epiphytes and community composition with their relation to host tree traits. Nevertheless, effective and strategic conservation of vascular epiphytes must be considered in Darjeeling Himalaya. [ABSTRACT FROM AUTHOR]

The relationship between species diversity and biomass/productivity is a major scientific question in ecology. Exploring this relationship is essential to understanding the mechanisms underpinning the maintenance of biodiversity. Positive, negative, and neutral relationships have been identified in controlled experiments and observational research. However, increasing evidence suggests that the effects of species diversity on aboveground biomass and productivity are influenced by biotic and abiotic factors, but it remains unclear whether scale‐dependent effects affect aboveground biomass and productivity. Herein, we used a generalized linear regression model and a structural equation model to explore relationships between species diversity and productivity/aboveground biomass under different scales and to investigate the effects of topographical factors and species diversity on ecosystem functioning. The results revealed a positive relationship between biodiversity and ecosystem functioning based on species diversity and aboveground biomass. Different sampling scales may impact the relationship between species diversity and ecosystem functioning. A positive relationship was found between species richness and productivity at medium and large scales; however, ambiguous relationships were found in productivity and other species diversity indices. Elevation was a key factor affecting both biomass and productivity. These results suggest that species diversity is not the only factor affecting biomass and productivity, and the positive correlation between species diversity and ecosystem functioning is mediated by abiotic factors. [ABSTRACT FROM AUTHOR]

Tree species are known to predominantly interact either with arbuscular mycorrhizal (AM) or ectomycorrhizal (EM) fungi. However, there is a knowledge gap regarding whether these mycorrhizae differently influence biodiversity–ecosystem functioning (BEF) relationships and whether a combination of both can increase community productivity. In 2015, we established a tree‐diversity experiment by growing tree communities with varying species richness levels (one, two, or four species) and either with AM or EM tree species or a combination of both. We investigated basal area and annual basal area increment from 2015 to 2020 as proxies for community productivity. We found significant positive relationships between tree species richness and community productivity, which strengthened over time. Further, AM and EM tree species differently influenced productivity; however, there was no overyielding when AM and EM trees grew together. EM tree communities were characterized by low productivity in the beginning but an increase of increment over time and showed overall strong biodiversity effects. For AM tree communities the opposite was true. Although young trees did not benefit from the presence of the other mycorrhizal type, dissimilar mechanisms underlying BEF relationships in AM and EM trees indicate that maximizing tree and mycorrhizal diversity may increase ecosystem functioning in the long run. [ABSTRACT FROM AUTHOR]

Continuous cover forestry maintains many characteristics of uneven-aged natural forests and aims to preserve biodiversity. Gap-cutting is a management option that may create a balance between timber production and continuous forest cover. We investigated the effect of newly created gaps on ground-dwelling spider assemblages in a managed oak forest, in the Pilis Mts., Hungary. Between 2018–2021 we sampled newly created elongated and circular-shaped gaps of two different sizes in a six-times replicated randomised complete block design. Pitfall samples of ~4600 spiders indicated that spider species richness was moderately higher in the gaps than in control stands. Spider assemblages did not respond in a specific way to the different gap implementations, but their variation in species composition was considerably higher in gaps than in the control plots. The excess spider abundance and species number in gaps, as compared to control, increased over the observation period, as did the dissimilarity of gap assemblages to control. Species responses imply that gaps create a variation in microhabitats and microclimatic conditions, resulting in spiders' diversification. The overall effect of gaps on spider assemblages suggests that gap-cutting is a suitable management option that preserves forest spider assemblages. [ABSTRACT FROM AUTHOR]

The physical structure of vegetation is thought to be closely related to ecosystem function, but little is known of its pertinence across geographic regions. Here, we used data from over three million trees in continental North America to evaluate structural diversity – the volumetric capacity and physical arrangement of biotic components in ecosystems – as a predictor of productivity. We show that structural diversity is a robust predictor of forest productivity and consistently outperforms the traditional measure – species diversity – across climate conditions in North America. Moreover, structural diversity appears to be a better surrogate of niche occupancy because it captures variation in size that can be used to measure realized niche space. Structural diversity offers an easily measured metric to direct restoration and management decision making to maximize ecosystem productivity and carbon sequestration. [ABSTRACT FROM AUTHOR]

Simple Summary: At present, the only place in Europe where the full development cycle of forests takes place on a large scale is the Białowieża Forest, because in most other forests dead or dying trees are eliminated, so the terminal (decay) phase does not occur there. Studies of animal assemblages inhabiting different forest phases are scarce as well as studies of spiders inhabiting tree trunks and branches. In this study, we compare spider assemblages inhabiting the tree trunks and branches in the optimal, terminal and regeneration phases of a primeval oak–lime–hornbeam stand in terms of their abundance, species diversity and species richness. We did not find differences in the total spider species richness between the analysed phases. However, we found that species diversity of both foliage-dwelling and trunk-dwelling spider assemblages was higher in the terminal phase compared to the other phases, which may indicate that this phase offers the most diverse niches for spiders as a result of the significant disturbance in the forest stand structure. Our research contributes to the understanding of the functioning of natural ecosystems, which can be useful for responsible forest management. The study was conducted in the Białowieża Forest, which is the only place in Europe where the full development cycle of forests takes place on a large scale. The objective of this study was to compare spider assemblages inhabiting tree trunks and tree branches in the optimal, terminal and regeneration phases of a primeval oak–lime–hornbeam stand, in terms of their abundance, species diversity and species richness. Spiders of tree branches were sampled using a sweep net into which branches were shaken, while spiders inhabiting tree trunks were collected using traps made of corrugated cardboard placed around the trunks. The three analysed phases did not differ in terms of total species richness. We found that the species diversity of both foliage-dwelling and trunk-dwelling spider assemblages was higher in the terminal phase compared to other phases, which may indicate that the former phase offered the most diverse niches for spiders as a result of the significant disturbance in the stand structure. In addition, we found fewer spider individuals and species in individual samples collected on tree branches from a plot in the regeneration phase compared to the other phases, which may be a consequence of the structure of the stand in this phase (low canopy cover, lush herbaceous vegetation). [ABSTRACT FROM AUTHOR]

Despite recent evidence from inventories and experimental forests indicating that high species richness among trees increases productivity and further improves soil organic carbon (SOC) storage, the mechanisms controlling the richness–SOC relationship are inconsistent. Hence, the optimal tree species richness required to increase SOC stocks needs to be further explored. Based on field observations from a subtropical mixed-species planted forest, which was established 40 years ago through a mosaic pattern of afforestation and natural regeneration, we examined the effects of tree species richness on the SOC stock and the chemical composition of SOC in the topsoil (top 10 cm layer). We found a quadratic relationship between tree species richness and SOC stocks. The threshold of tree species richness appeared between four and five. Tree species richness affected the SOC stocks primarily by increasing the quantity of leaf litter, and while decreasing the quality of leaf litter and fine root. In addition, tree species richness changed the chemical composition of SOC by affecting the chemical composition of the plant carbon, and soil bacterial α-diversity, thereby affecting the SOC stock. The trade-off between leaf litter and fine root C sources contributed to the quadratic relationship between tree species richness and SOC stocks. These results show that the mixing of 4–5 tree species can achieve a higher SOC level than having fewer or more tree species in a planted subtropical forest. [ABSTRACT FROM AUTHOR]

The increasing disturbances in monocultures around the world are testimony to their instability under global change. Many studies have claimed that temporal stability of productivity increases with species richness, although the ecological fundamentals have mainly been investigated through diversity experiments. To adequately manage forest ecosystems, it is necessary to have a comprehensive understanding of the effect of mixing species on the temporal stability of productivity and the way in which it is influenced by climate conditions across large geographical areas.Here, we used a unique dataset of 261 stands combining pure and two‐species mixtures of four relevant tree species over a wide range of climate conditions in Europe to examine the effect of species mixing on the level and temporal stability of productivity. Structural equation modelling was employed to further explore the direct and indirect influence of climate, overyielding, species asynchrony and additive effect (i.e. temporal stability expected from the species growth in monospecific stands) on temporal stability in mixed forests.We showed that by adding only one tree species to monocultures, the level (overyielding: +6%) and stability (temporal stability: +12%) of stand growth increased significantly. We identified the key effect of temperature on destabilizing stand growth, which may be mitigated by mixing species. We further confirmed asynchrony as the main driver of temporal stability in mixed stands, through both the additive effect and species interactions, which modify between‐species asynchrony in mixtures in comparison to monocultures.Synthesis and applications. This study highlights the emergent properties associated with mixing two species, which result in resource efficient and temporally stable production systems. We reveal the negative impact of mean temperature on temporal stability of forest productivity and how the stabilizing effect of mixing two species can counterbalance this impact. The overyielding and temporal stability of growth addressed in this paper are essential for ecosystem services closely linked with the level and rhythm of forest growth. Our results underline that mixing two species can be a realistic and effective nature‐based climate solution, which could contribute towards meeting EU climate target policies. [ABSTRACT FROM AUTHOR]

Amazonian floodplain forests along large rivers consist of two distinct floras that are traced to their differentiated sediment- and nutrient-rich (várzea) or sediment- and nutrient-poor (igapó) environments. While tree species in both ecosystems have adapted to seasonal floods that may last up to 270–300 days year−1, ecosystem fertility, hydrogeomorphic disturbance regimes, water shortage and drought, fire, and even specific microclimates are distinct between both ecosystems and largely explain the differences in forest productivity and taxonomic composition and diversity. Here, we review existing knowledge about the influence of these environmental factors on the tree flora of both ecosystems, compare species composition and diversity between central Amazonian várzeas and igapós, and show that both ecosystems track distinct species life-history traits. The ecosystem-level and taxonomic differences also largely explain the biogeographic connections of várzeas and igapós to other Amazonian and extra-Amazonian ecosystems. We highlight the major evolutionary force of large-river wetlands for Amazonian tree diversity and explore the scenarios by which the large number of Amazonian floodplain specialist tree species might even contribute to the gamma diversity of the Amazon by generating new species. Finally, we call attention to the urgent need of an improved conservation of Amazonian várzea and igapó ecosystems and their tree species. [ABSTRACT FROM AUTHOR]

Fine roots (φ ≤ 2 mm) play an important role in the process of material and nutrient cycling in forest ecosystems, but the effect of tree species diversity on the functional characteristics of fine roots is unclear. In this study, 1−7 subtropical communities with different species richness were selected to study the morphological characteristics, productivity (PRO), and turnover rate (TUR) of fine roots by continuous soil core extraction, ingrowth soil core method, and root analysis system. The effects of tree species diversity on fine root morphological characteristics, PRO, and TUR are also analyzed. The results showed that with the increase in tree species diversity in the community, the effect of fine root morphological characteristics including specific root length (SRL) and specific surface area (SSA) of each community was not significant, but the fine root PRO in the community increased from 71.63 g·m−2·a−1 (Ligustrum lucidum pure forest) to 232.95 g·m−2·a−1 (Cinnamomum camphora mixed forest with seven species richness communities), and the fine root TUR increased from 0.539 times·a−1 to 0.747 times·a−1. Correlation analysis and redundancy analysis showed that species richness, root functional traits, and soil physicochemical properties were important driving factors affecting root characteristics. The increase in tree species diversity did not change the morphological characteristics of fine roots but increased the PRO and TUR of fine roots. [ABSTRACT FROM AUTHOR]

Ecological theory suggests that species with complementary architectural and physiological traits can optimize crown packing to improve resource efficiency and promote ecosystem productivity in forest communities. However, empirical evidence of this prediction is rare in species-rich natural forests, as little is known about how crown spatial complementarity regulates community species richness-productivity relationship (SRPR). In this study, we measured tree architectural traits (stem diameter, height, crown depth and width) for 11,337 trees, and quantified species richness, functional diversity, crown spatial complementarity, soil fertility and forest productivity for 44 quadrats (20 m × 20 m per quadrat) in the Badagongshan 25 ha forest plot, central China. We tested bivariate correlations between species richness, crown complementarity, functional diversity and forest productivity. We employed linear mixed effects models to predict crown complementarity and examined its relationship with functional diversity. Finally, we applied structural equation modeling to quantify the mediation effects of crown complementarity on SRPRs. Species richness promoted crown complementarity and forest productivity. Crown complementarity varied across quadrats, with increases driven primarily by changes in tree height. Crown complementarity was positively related to functional diversity and forest productivity. Species richness increased with soil total phosphorus, while functional diversity decreased with soil bulk density. Forest productivity increased with soil organic carbon and total nitrogen, but decreased with bulk density. Crown complementarity partially mediated the positive effect of species richness on forest productivity, and the mediation effect was mainly through functional diversity. Our results suggest that the crown complementarity index accurately reflects the niche complementarity through light utilization and carbon reallocation. Our study emphasizes that species richness can promote crown complementarity, leading to greater forest productivity, which provides greater insight into the mechanical understanding of the SRPRs. [ABSTRACT FROM AUTHOR]

• Increased tree species richness boosts soil N mineralization. • Leaf N and soil moisture predict soil N mineralization. • Monoculture forests display a negative link between N mineralization and tree productivity. • No significant correlation existed between N mineralization and tree productivity in mixed forests. • Tree species diversity can mitigate N limitation in subtropical forests. Forest ecosystems are facing declining plant species diversity. However, the effects of reduced tree species diversity on soil nutrient supply and tree productivity remain poorly understood. We conducted a biodiversity-ecosystem function experiment with a range of subtropical tree species richness (1, 4, 8, 16, and 32) to investigate the impacts of tree species diversity on soil net nitrogen (N) mineralization rates and its regulation on tree productivity in a young subtropical forest experiment. Our findings indicate a log-linear trend between soil net N mineralization rates and tree species richness, potentially suggesting an improvement in soil N supply capacity with greater species richness. Leaf N content, soil water content and peroxidase enzyme activity were identified as primary positive predictors influencing soil net N mineralization rates. In monoculture forests, soil net N mineralization rates were negatively correlated with litter production and tree basal area, while no such correlation was observed in mixed forests. This implies that soil net N mineralization rates play a critical role in tree productivity for monoculture forests. Together, these results provide strong evidence that the rate of decrease in soil nutrient supply capacity potential accelerates with the loss of tree species diversity in young tree communities, and highlights the importance of increasing tree species diversity to mitigate nutrient limitations. Therefore, preserving tree species diversity is crucial for the future functionality of ecosystems amidst global biodiversity loss. [ABSTRACT FROM AUTHOR]

The Biodiversity – Ecosystem Functioning (B–EF) relationship remains a topic of ongoing debate with most studies focusing on primary productivity, and documenting that this relationship takes many forms. It remains unclear if biodiversity drives productivity or productivity shapes biodiversity or the relationship is bidirectional. B-EF studies explore almost exclusively the relationship between species richness and ecosystem functioning, while the role of biotic interactions, a key component of ecosystem functioning, has been neglected. Here, using data of 80 local plant–pollinator networks on 20 Aegean islands, and of gross primary productivity (GPP) from the MODIS satellite, we explored the bidirectional relationship between interaction network structure (nestedness and specialization), species richness (plants and pollinators) and mean and inter-annual variability of GPP. We found that nestedness and specialisation of plant–pollinator networks is driven by mean GPP. However, specialisation alone was a significant predictor of mean GPP, implying that networks tend to be more specialised in low-productivity areas. Pollinator species richness exerted a strong effect on mean GPP with the remaining factors playing a minor role, while the effect of mean GPP on pollinator species richness was weaker. Furthermore, the nestedness of plant–pollinator networks drives inter-annual variability of GPP with more nested networks displaying less variability, which is in accordance with the predictions of the insurance hypothesis. Plant and pollinator species richness were also associated with inter-annual variability of GPP. [Display omitted] [ABSTRACT FROM AUTHOR]

Retention forestry is a common practice for biodiversity conservation in forests managed for wood production. Retention forestry often leaves unharvested patches of trees that vary in size and spatial pattern but experiments evaluating the effects of different retention patch configurations at a constant level of retention are lacking for many regions and taxonomic groups. We implemented an experimental study in clearcut conifer stands with retention across the U.S. Pacific Northwest region. The study consisted of five stand-level (11–55 ha) experimental treatments each replicated 10 times within a randomized complete block design, resulting in 50 treated stands. Retained tree density was comparable across treatments but size, number, and location (upland or riparian) of patches within stands varied among the five treatments. Within experimental treatments, we measured small mammal (<1kg) species and functional trait (i.e., body size, diet, activity stratum) richness in retention patches, surrounding harvested portions of stands, and nearby unharvested stands. We evaluated species and functional trait richness by treatment using generalized linear mixed-effects models and species-specific responses to retention placement using a community occupancy model. We obtained repeat captures of 21 species of small mammals but found limited evidence of a treatment effect on species richness, and no differences in functional trait richness. Species richness was highest where all retained trees were aggregated into one patch placed adjacent to a forested riparian buffer (mean = 6.6 species, 95% CI = 5.7–7.5), and lowest in the treatment containing one retention patch in the upland portion of a harvested stand (mean = 4.7 species, 95% CI = 3.8–5.6). Furthermore, estimates of species richness within retention patches of harvested stands (i.e., not considering species in harvested areas) did not differ among treatments, indicating that the slightly elevated species richness in riparian-associated retention results from 1–2 species in these patches that do not occur in adjacent harvested portions of each treated stand. Patch occupancy of several species was higher in riparian patches than harvested portions of the treated stands, and fewer species had higher occupancy in upland patches compared to harvested portions of treated stands. Our results indicated that at retention densities currently required in Oregon and Washington, the location of retention patches had a small influence on stand-scale measures of small mammal diversity, but local increases in species richness may be obtained by retaining trees adjacent to riparian buffers. [ABSTRACT FROM AUTHOR]

Previous studies have demonstrated that tree species diversity increases productivity and may enhance nutrient cycling in forests. The effect of mixing tree species on stand‐level nutrient use efficiency (NutUE) has seldom been studied, and even less so in the context of climate change. Here we present the first study examining how diversity effects on NutUE may be modified by growing season water availability (low vs. high), and importantly, during periodic drought or on water‐limited sites.We tested the interaction of water availability and tree species diversity (i.e. species richness and species identity) on NutUE in two young, experimental plantations located in south‐western France (ORPHEE), and northern Ontario, Canada (IDENT‐SSM). We calculated stand‐level NutUE as above‐ground net primary productivity (ANPP) divided by the product of litterfall mass and macronutrient concentrations, of monocultures and mixed tree communities composed of several temperate tree species, with a focus on birch and pine at both sites.We found significant species richness and water availability effects on NutUE, but they were weakly and inconsistently expressed, detected only for specific nutrients, and differed between the two sites. Species identity had much stronger effects on NutUE when examined using the birch–pine plots at both sites. At ORPHEE, nitrogen use efficiency (NUE) and phosphorus use efficiency (PUE) were significantly greater in the birch–pine mixture than in each monoculture. This was due to an increase in ANPP coupled with a decrease in litter nutrient concentrations in the two‐species plot that was driven by the dominance of pine in the mixture. In the comparatively younger, denser plots at IDENT‐SSM, birch was the dominant species that resulted in positive mixing effects on ANPP and litter nutrient concentrations and a neutral effect of mixing on NUE and PUE in the birch–pine mixture.Overall, the effects of mixing did not differ with water availability treatments, suggesting that species composition of mixtures is more important than water availability for stand‐level NutUE in these young forest communities. Read the free Plain Language Summary for this article on the Journal blog. [ABSTRACT FROM AUTHOR]

Biodiversity effects on ecosystem functioning can be partitioned into complementarity effects, driven by many species, and selection effects, driven by few. Selection effects occur through interspecific abundance shifts (dominance) and intraspecific shifts in functioning. Complementarity and selection effects are often calculated for biomass, but very rarely for secondary productivity, that is, energy transfer to higher trophic levels. We calculated diversity effects for three functions: aboveground biomass, insect herbivory and pathogen infection, the latter two as proxies for energy transfer to higher trophic levels, in a grassland experiment (PaNDiv) manipulating species richness, functional composition, nitrogen enrichment, and fungicide treatment. Complementarity effects were, on average, positive and selection effects negative for biomass production and pathogen infection and multiple species contributed to diversity effects in mixtures. Diversity effects were, on average, less pronounced for herbivory. Diversity effects for the three functions were not correlated, because different species drove the different effects. Benefits (and costs) from growing in diverse communities, be it reduced herbivore or pathogen damage or increased productivity either due to abundance increases or increased productivity per area were distributed across different plant species, leading to highly variable contributions of single species to effects of diversity on different functions. These results show that different underlying ecological mechanisms can result in similar overall diversity effects across functions. [ABSTRACT FROM AUTHOR]

Estimating forest above‐ground biomass (AGB) productivity constitutes one of the most fundamental topics in forest ecological research. Based on a 30‐ha permanent field plot in Northeastern China, we modeled AGB productivity as output, and topography, species diversity, stand structure, and a stand density variable as input across a series of area scales using the Random Forest (RF) algorithm. As the grain size increased from 10 to 200 m, we found that the relative importance of explanatory variables that drove the variation of biomass productivity varied a lot, and the model accuracy was gradually improved. The minimum sampling area for biomass productivity modeling in this region was 140 × 140 m. Our study shows that the relationship of topography, species diversity, stand structure, and stand density variables with biomass productivity modeled using the RF algorithm changes when moving from scales typical of forest surveys (10 m) to larger scales (200 m) within a controlled methodology. These results should be of considerable interest to scientists concerned with forest assessment. [ABSTRACT FROM AUTHOR]

This study investigates the bending performances of full-size and green glued laminated timber (glulam) beams, manufactured under a tropical climate. Two types of beams were prepared: mono-species and mixedspecies glulam. The mono-species glulam with uniform layup were manufactured using abura (Mitragyna ciliata) and dabema (Piptadeniastrum africanum). The mixed-species glulam with balanced layup were manufactured by associating difou (Morus mesozygia) and abura, and tali (Erythrophleum ivorense) and dabema. These species were selected in the framework of a sustainable development of the glulam industry in Congo Basin, and clustering of their technological properties. A one component polyurethane adhesive was used, and the beams were dried artificially using vacuum. Pure bending tests were performed and the results showed an optimal bondlines thickness that ranged from 0.1 to 0.3 mm. Failure occurred in the solid woods indicating a satisfatory bonding quality of the glulam products. The strength properties of the glulam and solid woods presented compatible trends. Findings of this study showed that it is possible to develop high mechanical performance glulam products while improving the valorisation of lesser-known species, thus preserving the forest diversity in the Congo Basin. [ABSTRACT FROM AUTHOR]

Although biodiversity has been shown to profoundly affect ecosystem function in forests, the processes which it impacts are limited understood. Various plant species with diverse sizes interact to form complex networks to complete resource use processes, but little is known about the role of species-size networks in influencing ecosystem function and biodiversity-ecosystem function relationships. Using a dataset encompassing 423 species and 32,067 individuals, we constructed species–tree diameter and species–tree height networks for two sampling areas (0.04 and 0.09 ha), and then calculated the network modularity for species and size interlinked specialization and nestedness, species or sizes with relatively few links are a subset of those with more network links. We analyzed the relationships between modularity, nestedness, and the aboveground biomass. The direct and indirect effects of species abundance and richness on the aboveground biomass through network structures were explored using structural equation modelling. Regardless of the species–tree diameter or height network, modularity was positively associated with the aboveground biomass, independent of the sampling area, while nestedness was negatively associated. Species abundance negatively affected the modularity, but positively affected nestedness, whereas species richness had the opposite effect. Species abundance and richness affected the aboveground biomass indirectly through modularity and nestedness, but the effect of modularity was greater than that of nestedness. Our study confirms that the importance of species–size networks in the context of the aboveground biomass has similar effects on species–diameter and height networks across sampling areas. It clarifies that modularity from interactions between species and individuals is a useful indicator to reveal the mechanism by which plant diversity acquires resources for biomass production. These results provide new insights into biodiversity–ecosystem function relationships from a network perspective.

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Questions: Livestock grazing is an important driver of plant diversity in grasslands. Different mechanisms summarized in three main hypotheses have been proposed to explain its varying effects depending on productivity. The insufficient compensation hypothesis (ICH) states that livestock causes the extinction of species that cannot compensate for biomass removal in unproductive sites, reducing species richness. The competitive release hypothesis (CRH) states that livestock increases plant diversity by attenuating competition, especially in productive environments. In the convergent evolution hypothesis (CEH), livestock has minor effects on diversity in unproductive sites because plants that endure stress are pre-adapted to grazing. These hypotheses have rarely been compared formally, and have mostly been tested on large spatial scales. Here we simultaneously test these hypotheses on a local scale. Location: Natural semi-arid grassland, Oaxaca, Mexico. Methods: We performed a long-term exclosure experiment, recording plant diversity annually over 17 years. In 2017 we measured species richness over a grazing intensity gradient. We used linear mixed-effects models, nestedness and beta-diversity analyses to evaluate diversity and composition in relation to grazing and productivity. Results: Plant diversity generally increased with grazing intensity. In line with CRH, species richness increased as grazing became more intensive due to a progressive incorporation of increasingly poor competitors to the community, with a seemingly stronger effect under high productivity. This suggests that herbivores limit competitive species and prevent competitive exclusion. ICH may play a secondary role because the effect was reversed in low productivity inside exclosures. Conclusions: Our finding implies that in productive sites, the exclusion of livestock can be detrimental to plant diversity as a lack of grazing accelerates competitive exclusion. By contrast, in limiting environments, grazing can preserve diversity if livestock are kept at low stocking densities. Our results show that small-scale variations in productivity need to be considered when designing livestock management. [ABSTRACT FROM AUTHOR]

Previous studies are most focusing on the species identification and habitat used by cuscus, while habitat changes are the most threats on cuscus. Habitat changes caused by the operation of logging concession such as PT Wijaya Sentosa creates an impact to the habitat selection of cuscus, which is highly dependent on forest cover. Efforts to protect cuscus species in production forests need to be carried out to ensure their sustainability habitat. This study aims to determine habitat preference of cuscus and model the suitability habitat of cuscus. The Neu index calculation is used to measure the level of habitat preference, while the habitat sustainability map is modelled by biotic, abiotic, and human disturbance components into MaxEnt application. Vegetation data is analyzed to describe tree density, tree richness, and strata using of cuscus by SexFI application. The study showed that the most preferred habitat by cuscus is LoA 2018 because LoA 2018 had the most species richness so cuscus might be able to choose their vegetation food. The habitat suitability of cuscus in PT Wijaya Sentosa covers 21,116.59 ha and didn't follow the pattern of increasing Et+ logging but was strongly influenced by logged blocks as much as 55.2% contribution. [ABSTRACT FROM AUTHOR]

Biodiversity is found to have a significant promotion effect on ecosystem functions in manipulation experiments on grassland communities. However, its relative role compared with stand factors or functional identity is still controversial in natural forests. Here, we examined their relative effects on biomass and productivity during forest restoration. We investigated stand biomass and productivity for 24 plots (600 m2) across restoration stages in the subtropical forests of Mt. Shennongjia, Central China. We measured five key functional traits and calculated functional diversity (functional richness, evenness and dispersion) and community-weighted mean of traits. We used general linear models, variation partitioning methods to test the relative importance of stand factors (density, stand age, maximum height, etc.), functional identity, species and functional diversity on biomass and productivity. Our results illustrated that stand biomass and productivity increased significantly as forest restoration, and that community species richness increased, while functional dispersion decreased significantly. Variation partitioning analyses showed that diversity had no significant pure effects on biomass and productivity. However, diversity may affect biomass and productivity through the joint effect with stand factors and functional identity. Overall, we found that stand factors had the strongest effect on biomass and productivity, while functional identity significantly affects productivity but not biomass, suggesting that modulating stand structure and species identity are effective ways to enhance forest carbon storage and sequestrations potential in forest management. [ABSTRACT FROM AUTHOR]

Context: Fire influences the distribution of ecosystems on Earth, but the link between pyrodiversity, the heterogeneity in post-fire conditions, and biodiversity is just emerging. Objectives: We tested the pyrodiversity begets biodiversity theory, which was developed at broader scales, to a scale where land management decisions are commonly made. Methods: To assess the effects of landscape attributes on avian species richness, we deployed programmable acoustic recorders at 34 sites in a frequently burned longleaf pine (Pinus palustris) ecosystem which were set to record three, five–minute sessions per day for six days for two years. We identified avian species by their vocalizations and grouped them by nesting and forging guilds to assess the effects of land cover type, soil productivity, forest structure and fire history characteristics including, pyrodiversity on species richness and occupancy at the community, guild, and species levels using hierarchical Bayesian multispecies occupancy models. We defined pyrodiversity as the richness in time since fire values around a site. Results: We found support for the pyrodiversity begets biodiversity hypothesis at the community level, as avian species richness increased with pyrodiversity (β = 0.136, 95% CrI 0.009–0.260). Species richness of cavity nesting species decreased with increasing time since fire, suggesting frequent fire increases diversity of this guild (β = − 0.334, 95% CrI − 0.713 to − 0.003). Conclusions: Our work highlights the importance of pyrodiversity as a driver for biodiversity, and links theory to practices by examining this phenomenon at a scale readily translated into conservation action. [ABSTRACT FROM AUTHOR]

Retention forestry has become increasingly popular in recent decades. Although retained trees have a high post-harvest mortality rate, little is known about the role of dead retention trees in the conservation of lichen and bryophyte species. In this study, species composition and richness of bryophytes and lichens on living trees, and snags and logs of dead retention trees was assessed in 20 young stands in Latvia. The goal was to compare how the species richness and composition differ between retention tree structure types (living trees, snags, and logs). The results showed that higher bryophyte and lichen species richness per tree was found on logs and snags compared to living trees. Species composition significantly differed between retention tree structure types. Snags and logs hosted a higher number of woodland key habitat species than living trees. Retention tree species had a significant effect on bryophyte species richness on living trees, while tree species and diameter at breast height were important for bryophyte diversity on snags, and stage of decay on logs. In contrast, the number of lichen species on snags and logs was affected only by retention tree species while none of these factors had a significant effect on lichen species on living trees. As a conclusion, the conservation of bryophyte and lichen diversity on retention trees needs to consider also their role as deadwood substrates after their death. • Bryophyte and lichen richness were compared on snags, logs and living retention trees. • Logs and snags had more bryophyte and lichen species than living retention trees. • More woodland key habitat species were on snags and logs compared to living trees. • Factors influencing species richness differ between living and dead retention trees. • Dead retention trees are valuable substrate for bryophyte and lichen conservation. [ABSTRACT FROM AUTHOR]

Positive relationships between structural diversity and forest productivity have been documented in controlled experiments and early secondary forests, however, negative relationships have also been observed in late successional forests. The mechanisms causing observed relationships between structural diversity and productivity are not well‐established, but complementarity among crowns and asymmetric competition have been suggested.We used LiDAR and repeated census data to examine the relationship between canopy structural diversity and productivity in nine 1‐ha subtropical forest plots along a disturbance gradient in southeastern China. We quantified the relative importance of community composition, species diversity, canopy structural diversity, leaf area index (LAI) and disturbance regime on productivity using piecewise structural equation modelling. We also tested how vertical leaf area distribution affected productivity.Contrary to many prior observations, we found a negative relationship between canopy structural diversity and forest productivity. The negative effect may stem from asymmetric competition between overstorey and understorey leaves, leading to a lower leaf area efficiency (i.e. wood production per leaf area). Asymmetric competition was suggested by a negative relationship between understorey leaf area and total productivity. Changes in community composition over the disturbance gradient, but not species diversity, had a significant effect on productivity.Synthesis. Our study suggests that leaf area and canopy structural diversity have contrasting effects on productivity in this subtropical forest, and this needs to be considered when estimating rates of carbon sequestration in secondary forests. The negative effect of asymmetric competition on productivity is comparable to that of the shift in species composition over succession, highlighting the role of canopy structural diversity in shaping forest productivity. [ABSTRACT FROM AUTHOR]

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