Effects Of Species Diversity Research Articles

Climate and mycorrhizae mediate the relationship of tree species diversity and carbon stocks in subtropical forests

Abstract It is increasingly being recognized that tree species diversity has positive effects on forest ecosystem carbon (C) stock. However, at broad spatial scales, this relationship may depend on climate conditions and species mycorrhizal associations. Here, observations from 667 forest plots in subtropical China were used to investigate the effects of species diversity, mean annual precipitation (MAP), mean annual temperature (MAT) and mycorrhizal type (arbuscular or ectomycorrhizal) on the forest C stock and its components (tree C stock, shrub layer C stock, herb layer C stock, litter layer C stock, root C stock and soil C stock). We found positive effect of tree species diversity on total forest C stock. MAP had positive effects on total forest C stock and its components, while MAT had consistently negative effects on total forest C stock and most of its components. Different levels of MAP and MAT did modulate the strength of effect of species diversity on forest C stock and its components. In addition, species diversity, MAT and MAP showed a significant positive relationship with arbuscular mycorrhiza‐associated tree C stock but had no or negative relationship with ectomycorrhiza‐associated tree C stock. Synthesis. Our results indicate that maintaining high level of species diversity may support the buffering of negative effects resulting from climate warming. Furthermore, under climate warming the specific C stock of AM trees can increase, which can potentially promote forest C stock. Taken together, our study suggests that afforestation policies should consider not only tree species diversity to increase forest C stock but also the effects of different tree mycorrhizal types.

Tree species composition and management influence short-term resilience to defoliation by Lymantria dispar L. in oak forests

The frequency and intensity of natural disturbances such as infestations by forest insect pests are expected to increase under a scenario of climate change. Thus, tools for monitoring the impact of these disturbance events at large spatial scales are required, together with appropriate management practices for enhancing the ability of forest ecosystems to overcome affectations by insect pests. Here, we used the Enhanced Vegetation Index (EVI) combined with ‘ground truth’ measurements to assess the effects of tree species diversity and forest management on the resistance, recovery and short-term (two years) resilience in mixed oak forests after a severe Lymantria dispar L. defoliation episode. Our results showed that, although neither diversity nor management influenced forest resistance to defoliation, both factors interacted and influenced EVI recovery after the disturbance event. This interaction revealed the complex role tree diversity plays in increasing (in managed forests) or decreasing (in unmanaged forests) resilience to defoliation, thereby suggesting that tree species composition may be more relevant than tree species diversity per se. Indeed, in the field we observed a variety of species-specific degrees of defoliation (e.g. higher in Quercus ilex L.), as well as the preference of L. dispar adults for ovipositing in unmanaged areas and on particular trees (Arbutus unedo L.) that were barely defoliated. In addition, we also found significant and positive effects of tree size (dbh) on avoiding defoliation damage. We thus make three management recommendations for increasing the resilience of oak forests to L. dispar defoliation: i) the application of continuous-cover silviculture (30% thinning intensity in basal areas), ii) the retention of larger trees, and iii) the maintenance of a preferential combination of tree species in mixed stands (e.g. Q. suber and Q. pubescens).

Multifactor relationships between the forest structure and water conservation function ofPicea crassifoliaKom. plantations in Qinghai Province, China

AbstractForest structure and ecosystem function/service relationships have attracted considerable attention; however, knowledge of how forest structure systematically affects water conservation function is still lacking. Such research is urgently needed in Qinghai Province, China's Water Tower, to guide forest structure optimization for plantations with weak water conservation functions. Since healthy, stable tree growth is crucial for forests to fulfill their water conservation functions, this study examined the impacts of forest structure on tree growth. We investigated 115 plots in Qinghai Province and analyzed tree size, size heterogeneity, species diversity, competition and spatial distribution effects on the individual tree growth and water conservation function ofPicea crassifoliaKom. using mixed‐effect and structural equation models, respectively. Forest structure was important in modulating tree growth and the water conservation function. Tree size had the greatest impact on growth performance and directly enhanced the water conservation function. High‐size heterogeneity increased the tree growth rate and directly and indirectly improved the water conservation function via competition. Both individual growth and water conservation function were negatively related to competition between trees. Species diversity promotedP. crassifoliagrowth under a given degree of neighbourhood competition and indirectly affected the water conservation function by increasing size heterogeneity and reducing competition. An uneven spatial distribution did not influence tree growth but positively affected the water conservation function. Therefore, we emphasize that for plantations to fulfill their water conservation functions, pure forests with homogeneous structures should be transformed into mixed forests with heterogeneous structures.

Impact of tree species diversity on throughfall deposition in a young temperate forest plantation

Throughfall deposition is an important pathway via which particles, aerosols and gases can move from the atmosphere to the forest floor, which can greatly impact forest biodiversity and functioning. Although throughfall deposition biochemistry has been well studied in forest ecosystems, less is known about how throughfall deposition is modified by tree species diversity. To disentangle the effects of tree species identity and diversity on throughfall deposition, we installed rain gauges in a 10-year-old tree diversity experiment. With these rain gauges, we monitored throughfall biweekly, and performed chemical analyses monthly for all the major ions (Na+, Cl−, SO42−-S, K+, Ca2+, Mg2+, PO43−-P, NO3−-N and NH4+-N), for a period of one year. Based on these data, we analysed species identity (i.e. whether throughfall deposition depended on the tree species present in the overstorey), and diversity effects (i.e. whether throughfall deposition depended on tree species richness). We confirmed species identity effects on throughfall deposition. Presence of pine led to higher throughfall deposition of inorganic nitrogen, and lower amounts of phosphorus, calcium and magnesium reaching the forest floor. Additionally, species characteristics and stand structural characteristics, i.e. basal area and canopy cover, emerged as key factors driving throughfall deposition of sodium, chloride, nitrate, sulphate and potassium. Tree species diversity effects on throughfall deposition were also present, mostly via increased basal area and canopy cover, leading to increased throughfall deposition of inorganic nitrogen, sulphate, chloride, sodium and potassium. Our findings thus suggest that tree species diversity enhances throughfall deposition of most ions that we analysed, potentially increasing nutrient availability for below-canopy plant communities. Given that inorganic nitrogen and sulphur are major atmospheric pollutants, increased deposition in mixed plots might affect ecosystem functioning. Further research will be needed to determine the extent of this impact.

Effects of tree species identity and diversity on young tree growth in a south subtropical plantation

To select the tree species assembly model for improving the productivity in south subtropical plantations, we carried out an experiment following a random block design with eight native tree species across a richness gradient of 1, 2, 4, and 6 species. The effects of tree species diversity and species mixing with different functional identities on the young tree growth were investigated in the 5th year of the experiment. The results showed that tree growth was not positively correlated with tree species richness. The growth of fast-growing tree species (Pinus massoniana and Mytilaria laosensis) in the monoculture was 2.5-4.5 times of the valuable broadleaved tree species (Castanopsis hystrix and Erythrophleum fordii) monoculture. Tree growth was significantly increased by 51.5%-132.8% in the conifer and broadleaved tree species mixing plantations and in the fast-growing and nitrogen fixation tree species mixing plantations, when two tree species or four tree species were mixed. There was no significant difference in tree growth among different tree species mixed types, when six tree species were mixed. The contents of soil nitrogen, phosphorus and organic matter were the main factors affecting tree growth. The results indicated that young tree growth could be improved through the selecting conifer and broadleaved tree species mixing, fast-growing and nitrogen fixation tree species mixing in south subtropical plantations.

Big-sized trees and species-functional diversity pathways mediate divergent impacts of environmental factors on individual biomass variability in Sri Lankan tropical forests

In tropical forests, several studies have explored the effects of environmental factors and tree species diversity as well as functional trait diversity and trait composition on aboveground biomass (AGB) stock. However, these abiotic and biotic effects on individual biomass variability (BioVar) are still largely unexplored, which limits our understanding of the plant-plant interactions for species coexistence. Here, we used the Partial Least Squares Structural Equation Models (PLS-SEMs), and other complementary analyses, on data from 189 tropical forest plots in Sri Lanka, to test the linkages amongst climate (a latent variable of solar radiation and potential evapotranspiration), soil (pH and cation exchange capacity), plot (plot size and stand density) conditions, big-sized trees, species-functional diversity, and BioVar. The PLS-SEMs showed that climate conditions decreased BioVar directly but increased indirectly via integrative promoting direct effects on soil conditions, species-functional diversity and big-sized trees. In contrast, soil conditions increased BioVar directly but decreased indirectly via integrative suppressing direct effects on species-functional diversity and big-sized trees. Interestingly, we found that the divergent indirect effects of climate and soil conditions on BioVar via big-sized trees mattered when the direct effect of big-sized trees on species-functional diversity was considered as compared to the reverse effect in PLS-SEMs. Also, the indirect positive effect of plot properties on BioVar was nearly equal to the direct effect because plot properties affected big-sized trees as similar as or lower than species-functional diversity. The positive effect of species-functional diversity on BioVar was mediated by the structural attributes of big-sized trees, indicating increased plant species co-existence. This study suggests that individual tree biomass variability (i.e., BioVar) should be considered for managing natural tropical forests in the context of the plant-plant interactions for species coexistence.

Interactive effects of tree species composition and water availability on growth and direct and indirect defences in Quercus ilex

Plant diversity has often been reported to decrease insect herbivory in plants. Of the numerous mechanisms that have been proposed to explain this phenomenon, how plant diversity influences plant defences via effects on growth has received little attention. In addition, plant diversity effects may be contingent on abiotic conditions (e.g. resource and water availability). Here, we used a long‐term experiment to explore the interactive effects of tree species composition and water availability on growth, direct (i.e. phenolics) and indirect (i.e. volatile organic compounds – VOCs) defences and leaf herbivory in Quercus ilex. We quantified herbivory by chewing insects, phenolic compounds and VOCs in Q. ilex trees growing in stands differing in tree species composition (Q. ilex, Q. ilex + Betula Pendula, Q. ilex + Pinus pinaster and Q. ilex + B. pendula + P. pinaster) and water availability (irrigated versus control). Both direct and indirect defences were affected by tree species composition, but such changes were not mediated by changes in tree stem diameter. Quercus ilex trees growing in stands with P. pinaster had the lowest concentration of both direct and indirect defences. Importantly, the effects of tree species composition on VOCs were exacerbated on irrigated blocks. Despite variation in defences, tree species composition did not affect herbivory in Q. ilex. Accordingly, we did not find any association between defences and insect herbivory. Our results suggest that changes in the micro‐environment rather than growth‐defence associations may mediate tree diversity effects on defences. In addition, reduced defensive investment in more diverse stands could negatively impact tree resistance masking the beneficial effects of species diversity at reducing insect herbivory.

Topography, Diversity, and Forest Structure Attributes Drive Aboveground Carbon Storage in Different Forest Types in Northeast China

Forests regulate air quality and respond to climate change by storing carbon. Assessing the driving factors of forest aboveground carbon (AGC) storage is of great importance for forest management. We assumed that different forest types would affect the relationship between species richness, stand density, individual tree size variation, and AGC. In order to test and verify it, we analyzed the inventory data of 206 fixed plots (20 m × 20 m) of Jingouling Forest Farm, taking advantage of the piecewise structural equation model (pSEM) to explore the effects of species diversity, stand structure attributes, and topography on the AGC storage in the Wangqing Forest in Jilin Province. In addition, in this study, we aimed to investigate whether the fixed factors (species diversity, stand structure attributes, and topography) influenced AGC storage more significantly than the random factor (forest type). According to the results of pSEM, the selected factors jointly explain the impact on 33% of AGC storage. The relationship between stand density and AGC is positive, and the impact of individual tree size variation on AGC storage is negative. Species richness has direct and indirect impacts on AGC storage, and the indirect impact is more significant through individual tree size variation. Both elevation and slope are significantly negatively associated with AGC storage. Forest type explains the impact on 12% of AGC storage, which means the relationship between AGC and predictors varies across forest types. The results provide a scientific basis for the protection and management decision of natural forests in northeastern China.

Spatial asynchrony matters more than alpha stability in stabilizing ecosystem productivity in a large temperate forest region

AbstractAimUnderstanding the biodiversity–stability relationship has become a central issue in ecology and conservation biology. Although the stabilizing effects of tree species diversity on ecosystem productivity are well recorded in small local communities, they remain poorly understood across scales (from local to larger spatial scales). This study evaluates biodiversity–stability effects from local to larger spatial scales in a large temperate forest region, considering a range of environmental conditions and environmental heterogeneity.LocationNorth‐eastern China (c. 700,000 km2).Time period2005–2017.Major taxa studiedWoody plants.MethodsWe define stability as the temporal invariability of biomass productivity. Regional metacommunities representing larger spatial scales were developed by aggregating multiple sets of local field plots. Simple regression analysis was used to test biodiversity–stability relationships in metacommunities. Piecewise structural equation modelling was then used to disentangle the effects of diversity and abiotic variables on forest stability at local and larger spatial scales. Multiple mixed‐effects regression models were used to determine the relative contribution of individual predictive variables to stability across spatial scales.ResultsWe found that local diversity (alpha diversity) was positively related to the stability of local communities (alpha stability), whereas species turnover across space (beta diversity) was positively related to asynchronous dynamics among local communities (spatial asynchrony), regardless of whether abiotic factors were considered or not. We also found that environmental conditions and environmental heterogeneity affected forest stability across scales. The effect of spatial asynchrony on gamma stability was greater than that of alpha stability.Main conclusionsOur results imply that spatial asynchrony is a key to maintaining the stability of ecosystem productivity within a large temperate forest region. We suggest that diverse forests and heterogeneous landscapes should be sustained at multiple spatial scales to buffer the negative effects of climate change and forest degradation.

Strata-dependent relationships among temperate forest structure, diversity, and growth rate along a local-scale environmental gradient

Exploring diversity-function relationships across overstory and understory strata is crucial for understanding ecological mechanisms, biodiversity conservation and forest management. In this study, we aimed to investigate the relationships among species diversity and stand structure, environmental factors, leaf area index (LAI), and the growth rate of overstory and understory strata in a mixed-broadleaf Korean Pine Forest in Northeast China. We performed structural equation models (SEMs) to evaluate the effects of environmental factors on overstory and understory species diversity, stand structure, and growth rate; the effects of overstory and understory species diversity and stand structure (total basal area, stem density, and diameter at the breast height variation) on the LAI and their respective growth rates; and the effect of overstory stratum on understory stratum species diversity, stand structure, and growth rate. Our results showed that species diversity determined the growth rate for overstory strata, while stem density was appropriate to determine understory growth rate. The integrative SEM accounted for 13, 13, 11, 8, and 7% of the variance in overstory species diversity, understory absolute growth rate, overstory absolute growth rate, understory stem density, and LAI, respectively. The diversity of overstory species had a positive direct influence on overstory growth but a negative direct effect on understory growth. Environmental factors (i.e., soil nutrients and soil moisture) positively influenced the understory growth rate but negatively influenced the overstory growth rate. Increasing understory stem density may increase the LAI; simultaneously, the LAI supported the understory growth rate. In natural forests, an arrangement between the overstory canopy and the availability of environmental resources is ideal for controlling species diversity and maximizing the productivity of both the overstory and understory strata.

树种多样性对土壤微生物群落结构和元素生物地球化学循环的影响研究进展

PDF HTML阅读 XML下载 导出引用 引用提醒 树种多样性对土壤微生物群落结构和元素生物地球化学循环的影响研究进展 DOI: 10.5846/stxb202101070073 作者: 作者单位: 作者简介: 通讯作者: 中图分类号: 基金项目: 国家自然科学面上项目(32071631)；国家自然科学基金青年基金项目(41907022)；福建省自然科学面上基金项目(2020J01138) Research progresses in the effects of tree species diversity on soil microbial communities and biogeochemical cycling of elements Author: Affiliation: Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:森林是陆地生态系统的重要组成部分,其巨大的生产力和生态服务功能对人类的生存和发展至关重要。森林树种多样性增加能够显著提高森林生产力,关于树种多样性如何影响地下生物多样性及生态功能逐渐受到国内外学者的广泛关注。从土壤微生物及其介导的元素生物地球化学循环这一视角出发,综述了树种多样性对土壤细菌和真菌多样性、群落结构及功能的影响,提出需要进一步深入研究的方向。总体来说,树种多样性有利于增加土壤细菌生物量和多样性,是预测病原性真菌和菌根真菌多样性及群落结构的重要生物因子。树种多样性能增加土壤有机碳储量,增强森林土壤的甲烷氧化能力,并提高土壤磷周转速率及有效磷含量。关于树种多样性对森林土壤氮循环的影响需考虑多样性假说和质量比假说的相对贡献。今后应加强树种多样性对多个营养级之间相互作用的研究;关注树种多样性对生态系统多功能的影响;加强学科交叉,引入微生物种群动态模型和气候模型等模型预测方法,研究树种多样性对全球气候变化的应对机制,以期促进地上植物多样性与地下生态系统功能关系的研究,增强森林生态系统应对未来全球环境变化的能力。 Abstract:Forest is an important component of terrestrial ecosystems. Its high productivity and ecosystem services play a key role in anthropogenic survival and development. The increases in forest tree species diversity can significantly increase forest productivity. It has been widely concerned about how tree species diversity influences the belowground biodiversity and ecosystem functioning. From the perspective of soil microorganisms and their mediated biogeochemical cycling of elements, we reviewed the effects of tree species diversity on soil bacterial and fungal diversity, community structure and ecosystem functioning, and further proposed future research directions. In general, tree species diversity is beneficial to increase soil bacterial biomass and diversity. Tree species diversity is an important bio-indicator of the diversity and community structure of pathogenic fungi and mycorrhizal fungi. Tree species diversity can increase soil organic carbon storage, and enhance soil methane oxidation capacity, as well as facilitate soil phosphorus turnover and bioavailability. The relative contribution of diversity hypothesis and mass ratio hypothesis should be taken into consideration in terms of the effects of tree species diversity on the nitrogen cycling. In the future, we should devote great efforts to the influence of tree species diversity on interactions among multiple trophic levels. Meanwhile, more attention should be paid to the effects of tree species diversity on ecosystem multifunctionality. Interdisciplinary research and modelling prediction methods, such as microbial population dynamics model and climate model, should be incorporated to explore the mechanisms of tree species diversity in response to global environmental change. This aims to promote the study on the relationship between aboveground plant diversity and belowground ecosystem functioning, and thus enhance the capacity of forest ecosystem for dealing with future global environmental change. 参考文献 相似文献 引证文献

Effects of plant species diversity, dominant species importance, and soil properties on glomalin-related soil protein

Effects of plant species diversity, dominant species importance, and soil properties on glomalin-related soil protein

Climatic conditions, not above- and belowground resource availability and uptake capacity, mediate tree diversity effects on productivity and stability

Tree species diversity promotes multiple ecosystem functions and services. However, little is known about how above- and belowground resource availability (light, nutrients, and water) and resource uptake capacity mediate tree species diversity effects on aboveground wood productivity and temporal stability of productivity in European forests and whether the effects differ between humid and arid regions. We used the data from six major European forest types along a latitudinal gradient to address those two questions. We found that neither leaf area index (a proxy for light uptake capacity), nor fine root biomass (a proxy for soil nutrient and water uptake capacity) was related to tree species richness. Leaf area index did, however, enhance productivity, but negatively affected stability. Productivity was further promoted by soil nutrient availability, while stability was enhanced by fine root biomass. We only found a positive effect of tree species richness on productivity in arid regions and a positive effect on stability in humid regions. This indicates a possible disconnection between productivity and stability regarding tree species richness effects. In other words, the mechanisms that drive the positive effects of tree species richness on productivity do not per se benefit stability simultaneously. Our findings therefore suggest that tree species richness effects are largely mediated by differences in climatic conditions rather than by differences in above- and belowground resource availability and uptake capacity at the regional scales.

The role of biodiversity in mitigating the effects of nutrient limitation and short-term rotations in plantations of subtropical China

Species diversity plays an essential role in enhancing ecosystem functions (EF) in both natural and plantation forests. However, we do not fully understand whether species diversity could maintain the sustainability of EFs in multiple-rotation plantations. Here, we hypothesized that tree species mixtures could mitigate declines in EFs along successive rotations, but could not maintain ecosystem multifunctionality. To test our hypothesis, we examined the effects of species diversity on four EFs, i.e., aboveground biomass (AGB), soil available nitrogen (SAN) and phosphorus (SAP), and soil organic matter (SOM), based on pure model simulation in plantations of subtropical China. The model fusion framework was set up by the integration of the process-based FORECAST and Multivariate Diversity-Interactions models. In the simulation, four local typical plantation tree species (two conifers, one evergreen broadleaf, and one deciduous N-fixing broadleaf) were selected and combined to form four monoculture and 11 mixture stands, and for each stand, the simulation was made for four 25-year rotations. The results showed that all the four EFs declined with the progress of rotations in both monoculture and mixtures, and the declining range was larger in monoculture than in mixtures in each rotation. Particularly, SAP significantly decreased while AGB, SAN, and SOM increased with diversity evenness from 0 (monoculture) to 1 (four species being equal abundant in the mixture). Overall, SAP and AGB displayed higher sensitivity to the disturbance of successive rotations compared with SAN and SOM. These results suggest that mixing species could not maintain EFs along with successive rotations because it could not alleviate SAP deficiencies in the soils resulted from the disturbances of silvicultural measures.

Increasing inputs of invasive N‐fixing Acacia litter decrease litter decomposition and associated microbial activity in streams

Abstract Nitrogen (N)‐fixing Acacia species are often aggressive invaders outside their native range. When invading native riparian temperate forests, they can decrease tree species diversity, alter the quality of litter inputs to streams and increase water N concentration. Although the effects of riparian tree species diversity and nutrient enrichment on litter decomposition and associated microbial decomposers have been widely studied, their individual and combined effects remain poorly understood, especially in streams flowing through forests invaded by Acacia species. Here, we assessed the effects of litter diversity (species evenness) and water N concentration on the decomposition of native and Acacia litter, and the activity and community structure of associated microbial decomposers. Litter of Castanea sativa (C) and Acacia melanoxylon (A) was enclosed in fine‐mesh bags in a total of five litter evenness treatments (100%C, 75%C + 25%A, 50%C + 50%A, 25%C + 75%A and 100%A), and immersed in a stream flowing through a native forest (native stream) and a stream flowing through a forest invaded by Acacia species (invaded stream). Litter decomposition rates and microbial decomposer activity differed among litter evenness treatments, generally decreasing as the proportion of A. melanoxylon increased. When considered individually, C. sativa litter decomposition and associated microbial activity did not differ among treatments. For A. melanoxylon, decomposition rates did not differ among treatments, whereas microbial activity was generally lower in treatments with higher or even proportions of C. sativa. Litter diversity had (small) antagonistic effects on litter decomposition in streams. However, litter treatments affected by diversity (species evenness) effects differed between streams, suggesting that effects can be modulated by water N concentration. Litter decomposition rates and microbial decomposer activity were higher in the invaded than in the native stream, probably as a consequence of the higher water N concentration in the former stream. However, the magnitude of the effects was small owing to the fact that water N concentration was still in the oligothrophic range in the invaded stream. Overall, our results suggest that the increasing proportion of N‐fixing Acacia species in invaded deciduous riparian forests will affect litter decomposition rates and microbial decomposer activity, and alter aquatic hyphomycete community structure, most probably as a result of decreases in the diversity and quality of litter inputs to streams, and increases in water N concentration. However, the magnitude of the effects resulting from decreases in litter input diversity and quality (due to increases in Acacia contribution) into invaded streams will probably be larger than those resulting from increases in water N concentration, thus overall litter decomposition will decrease. These impacts will possibly alter nutrient cycles in aquatic food webs that depend on riparian detritus, with implications for stream functioning.

Community genomics: a community-wide perspective on within-species genetic diversity.

Community genomics: a community-wide perspective on within-species genetic diversity.

Plant diversity with species drilled in the same or alternate rows enhanced pasture yield and quality over 4 years

This paper reports on the effects of plant species diversity and sowing method on pasture yield and quality. Nineteen seed mixtures of perennial ryegrass (PR), plantain (Pl), white clover (WC) and red clover (RC) were sown on 26 March 2015 at Lincoln University. Four mixtures of PR, Pl and WC were repeated with species separated in alternate drill rows. Plots were grazed by sheep and irrigated. After 4 years, a mixture with 25% of each species based on seed count – equivalent to 7.5 kg PR, 5.6 kg Pl, 1.9 kg WC and 4.4 kg RC (19.4 kg total seed)/ha – produced an optimal balance of increased total yield (17.44 t DM/ha/yr), weed suppression (0% of total yield), metabolisable energy (11.4 MJ/kg DM) and crude protein (19% of DM). Sowing method had no effect. Plant diversity enhanced pasture production through positive interactions and identity effects among the legumes (WC and RC) and non-legumes (PR and Pl). The strength of interactions between species depended on the identity and relative abundances of the species involved. The diversity effects occurred alongside shifts in species relative abundances over time. This study demonstrated an experimental basis for the evaluation of multi-species pasture mixtures.

Soil depth alters the effect of species diversity on productivity in an experimental karst herbaceous community

Soil depth alters the effect of species diversity on productivity in an experimental karst herbaceous community

Interactive effects of tree species mixture and climate on foliar and woody trait variation in a widely distributed deciduous tree

Abstract Despite increasing reports of severe drought and heat impacts on forest ecosystems, community‐level processes, which could potentially modulate tree responses to climatic stress, are rarely accounted for. While numerous studies indicate a positive effect of species diversity on a wide range of ecosystem functions and services, little is known about how species interactions influence tree responses to climatic variability. We quantified the intraspecific variation in 16 leaf and wood physiological, morphological and anatomical traits in mature beech trees (Fagus sylvatica L.) at six sites located along a climatic gradient in the French Alps. At each site, we studied pure beech and mixed stands with silver fir (Abies alba Mill.) or downy oak (Quercus pubescens Willd.). We tested how functional traits differed between the two species mixtures (pure vs. mixed stands) within each site and along the climatic gradient. We found significant changes in many traits along the climatic gradient as conditions progressively got drier and warmer. Independent of the mixture, reduced leaf‐level CO2 assimilation, stomatal size and thicker leaf cuticles, consistent with a more conservative resource use strategy, were found. At the drier sites, higher foliar stable carbon isotopic composition (δ13C), thicker mesophyll tissues and lower specific leaf area (SLA) in pure stands suggest that beech had more acquisitive traits there compared to mixed stands. At the wetter sites, trees in beech‐silver fir mixtures had higher chlorophyll concentration, lower δ13C, larger xylem vessels and higher SLA, suggesting a more acquisitive resource use strategy in mixed stands than in pure stands. Our work revealed that species interactions are significant modulators of functional traits, and that they can be just as important drivers of intraspecific trait variation as climatic conditions. We show that downy oak mixtures lead to an adaptive drought response by common beech in dry environments. In contrast, in milder climates, interactions with silver fir seem to increase beech resource acquisition and productivity. These findings highlight a strong context dependency and imply that incorporating local interspecific interactions in research on climate impacts could improve our understanding and predictions of forest dynamics. A free Plain Language Summary can be found within the Supporting Information of this article.

Species diversity and food web structure jointly shape natural biological control in agricultural landscapes

Land-use change and agricultural intensification concurrently impact natural enemy (e.g., parasitoid) communities and their associated ecosystem services (ESs), i.e., biological pest control. However, the extent to which (on-farm) parasitoid diversity and food webs mediate landscape-level influences on biological control remains poorly understood. Here, drawing upon a 3-year study of quantitative parasitoid-hyperparasitoid trophic networks from 25 different agro-landscapes, we assess the cascading effects of landscape composition, species diversity and trophic network structure on ecosystem functionality (i.e., parasitism, hyperparasitism). Path analysis further reveals cascaded effects leading to biological control of a resident crop pest, i.e., Aphis gossypii. Functionality is dictated by (hyper)parasitoid diversity, with its effects modulated by food web generality and vulnerability. Non-crop habitat cover directly benefits biological control, whereas secondary crop cover indirectly lowers hyperparasitism. Our work underscores a need to simultaneously account for on-farm biodiversity and trophic interactions when investigating ESs within dynamic agro-landscapes.