Biodiversity effects on ecosystem functioning: insights from aquatic systems

Unprecedented rates of species extinctions have prompted extensive research into the consequences of biodiversity losses on ecosystem functioning. While aquatic species are most threatened, research with freshwater and marine model systems has lagged behind progress made in terrestrial environments. This editorial to a special feature summarizes the main outcomes of a conference aimed at setting the stage for exploring the potential of aquatic systems to assess the role of biodiversity in ecosystem functioning. This series of papers proposes fresh approaches to the study of biodiversity effects on ecosystem functioning, outlines a new way of analyzing experimental data, presents a model that considers scale as an important factor determining outcomes, explores the effects of multiple stressors on species richness and ecosystem processes, and develops a food-web perspective that relates ecosystem properties to biodiversity. An insightful synthesis of lessons learned from aquatic systems is premature at present, but the papers clearly demonstrate the role that marine and freshwater systems can play in resolving open questions. The implications go well beyond the biodiversity in, and functioning of, ecosystems shaped by free-flowing or standing water.     

Ground‐dwelling arthropod communities across braided river landscape mosaics: a Mediterranean perspective

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Predator diversity effects cascade across an ecosystem boundary

Food webs in different ecosystems are often connected through spatial resource subsidies. As a result, biodiversity effects in one ecosystem may cascade to adjacent ecosystems. I tested the hypothesis that aquatic predator diversity effects cascade to terrestrial food webs by altering a prey subsidy (biomass and trophic structure of emerging aquatic insects) entering terrestrial food webs, in turn altering the distribution of a terrestrial consumer (spider) that feeds on emerging aquatic insects. Fish presence, but not diversity, altered the trophic structure of emerging aquatic insects by strongly reducing the biomass of emerging predators (dragonflies) relative to non‐feeding taxa (chironomid midges). Fish diversity reduced emerging insect biomass through enhanced effects on the most common prey taxa: predatory dragonflies Pantala flavescens and non‐feeding chironomids. Terrestrial spiders (Tetragnathidae) primarily captured emerging chironomids, which were reduced in the high richness (3 spp.) treatment relative to the 1 and 2 species treatments. As a result, terrestrial spider abundance was lower above pools with high fish richness (3 species) than pools with 1 and 2 species. Synergistic predation effects were mostly limited to the high richness treatment, in which fish occupied each level of vertical microhabitat in the water‐column (benthic, middle, surface). This study demonstrates that predator diversity effects are not limited to the habitat of the predator, but can propagate to adjacent ecosystems, and demonstrates the utility of using simple predator functional traits (foraging domain) to more accurately predict the direction of predator diversity effects.     

Toxic phytoplankton as a keystone species in aquatic ecosystems: stable coexistence to biodiversity

The effect of allelochemicals released by toxic species in plankton community is often taken into account to reveal plankton biodiversity. Using a minimal chemostat model we show that the interaction between toxic and non‐toxic phytoplankton species with changing competitive effects among species due to allelopathy helps to promote the stable coexistence of many species on a single resource and hence can solve the paradox of plankton. We emphasize toxic phytoplankton as a keystone species that strongly uncovers its allelochemicals on other non‐toxic phytoplankton and enhances the species persistence and diversity in aquatic ecosystems. In addition, we analyze the consistency of ecosystem functioning and species diversity using a number of approaches, such as sampling hypothesis with selection and complementarity effects, cascading extinction–reinvasion, and examining system dynamics at different enrichment levels and toxicity. Our results suggest that chemostats with one toxic and one or more nontoxic phytoplankton species can be used for the experimental verification of the stable coexistence of many species on a single resource in aquatic ecology.     

Biodiversity and ecosystem functioning decoupled: invariant ecosystem functioning despite non‐random reductions in consumer diversity

Most research that demonstrates enhancement and stabilization of ecosystem functioning due to biodiversity is based on biodiversity manipulations within one trophic level and measuring changes in ecosystem functions provided by that same trophic level. However, it is less understood whether and how modifications of biodiversity at one trophic level propagate vertically to affect those functions supplied by connected trophic levels or by the whole ecosystem. Moreover, most experimental designs in biodiversity–ecosystem functioning research assume random species loss, which may be of little relevance to non‐randomly assembled communities. Here, we used data from a published ecotoxicological experiment in which an insecticide gradient was applied as an environmental filter to shape consumer biodiversity. We tested how non‐random consumer diversity loss affected gross primary production (an ecosystem function provided by producers) and respiration (an ecosystem function provided by the ecosystem as whole) in species‐rich multitrophic freshwater communities (total of 128 macroinvertebrate and 59 zooplankton species across treatments). The insecticide decreased and destabilized macroinvertebrate and, to a lesser extent, zooplankton diversity. However, these effects on biodiversity neither affected nor destabilized any of the two studied ecosystem functions. The main reason for this result was that species susceptible to environmental filtering were different from those most strongly contributing to ecosystem functioning. The insecticide negatively affected the most abundant species, whereas much less abundant species had the strongest effects on ecosystem functioning. The latter finding may be explained by differences in body size and feeding guild membership. Our results indicate that biodiversity modifications within one trophic level induced by non‐random species loss do not necessarily translate into changes in ecosystem functioning supported by other trophic levels or by the whole community in the case of limited overlap between sensitivity and functionality.     

Biodiversity and ecosystem functioning in naturally assembled communities

Approximately 25 years ago, ecologists became increasingly interested in the question of whether ongoing biodiversity loss matters for the functioning of ecosystems. As such, a new ecological subfield on Biodiversity and Ecosystem Functioning (BEF) was born. This subfield was initially dominated by theoretical studies and by experiments in which biodiversity was manipulated, and responses of ecosystem functions such as biomass production, decomposition rates, carbon sequestration, trophic interactions and pollination were assessed. More recently, an increasing number of studies have investigated BEF relationships in non‐manipulated ecosystems, but reviews synthesizing our knowledge on the importance of real‐world biodiversity are still largely missing. I performed a systematic review in order to assess how biodiversity drives ecosystem functioning in both terrestrial and aquatic, naturally assembled communities, and on how important biodiversity is compared to other factors, including other aspects of community composition and abiotic conditions. The outcomes of 258 published studies, which reported 726 BEF relationships, revealed that in many cases, biodiversity promotes average biomass production and its temporal stability, and pollination success. For decomposition rates and ecosystem multifunctionality, positive effects of biodiversity outnumbered negative effects, but neutral relationships were even more common. Similarly, negative effects of prey biodiversity on pathogen and herbivore damage outnumbered positive effects, but were less common than neutral relationships. Finally, there was no evidence that biodiversity is related to soil carbon storage. Most BEF studies focused on the effects of taxonomic diversity, however, metrics of functional diversity were generally stronger predictors of ecosystem functioning. Furthermore, in most studies, abiotic factors and functional composition (e.g. the presence of a certain functional group) were stronger drivers of ecosystem functioning than biodiversity per se. While experiments suggest that positive biodiversity effects become stronger at larger spatial scales, in naturally assembled communities this idea is too poorly studied to draw general conclusions. In summary, a high biodiversity in naturally assembled communities positively drives various ecosystem functions. At the same time, the strength and direction of these effects vary highly among studies, and factors other than biodiversity can be even more important in driving ecosystem functioning. Thus, to promote those ecosystem functions that underpin human well‐being, conservation should not only promote biodiversity per se, but also the abiotic conditions favouring species with suitable trait combinations.     

Non‐additive effects of litter mixing are suppressed in a nutrient‐enriched stream

Investigations of how species compositional changes interact with other aspects of global change, such as nutrient mobilization, to affect ecosystem processes are currently lacking. Many studies have shown that mixed species plant litters exhibit non‐additive effects on ecosystem functions in terrestrial and aquatic systems. Using a full‐factorial design of three leaf litter species with distinct initial chemistries (carbon:nitrogen; C:N) and breakdown rates (Liriodendron tulipifera, Acer rubrum and Rhododendron maximum), we tested for additive and non‐additive effects of litter species mixing on breakdown in southeastern US streams with and without added nutrients (N and phosphorus). We found a non‐additive (antagonistic) effect of litter mixing on breakdown rates under reference conditions but not when nutrient levels were elevated. Differential responses among single‐species litters to nutrient enrichment contributed to this result. Antagonistic litter mixing effects on breakdown were consistent with trends in litter C:N, which were higher for mixtures than for single species, suggesting lower microbial colonization on mixtures. Nutrient enrichment lowered C:N and had the greatest effect on the lowest‐ (R. maximum) and the least effect on the highest‐quality litter species (L. tulipifera), resulting in lower interspecific variation in C:N. Detritivore abundance was correlated with litter C:N in the reference stream, potentially contributing to variation in breakdown rates. In the nutrient‐enriched stream, detritivore abundance was higher for all litter and was unrelated to C:N. Thus, non‐additive effects of litter mixing were suppressed by elevated streamwater nutrients, which increased nutrient content of all litter, reduced variation in C:N among litter species and increased detritivore abundance. Nutrients reduced interspecific variation among plant litters, the base of important food web pathways in aquatic ecosystems, affecting predicted mixed‐species breakdown rates. More generally, world‐wide mobilization of nutrients may similarly modify other effects of biodiversity on ecosystem processes.     

A general biodiversity–function relationship is mediated by trophic level

Species diversity affects the functioning of ecosystems, including the efficiency by which communities capture limited resources, produce biomass, recycle and retain biologically essential nutrients. These ecological functions ultimately support the ecosystem services upon which humanity depends. Despite hundreds of experimental tests of the effect of biodiversity on ecosystem function (BEF), it remains unclear whether diversity effects are sufficiently general that we can use a single relationship to quantitatively predict how changes in species richness alter an ecosystem function across trophic levels, ecosystems and ecological conditions. Our objective here is to determine whether a general relationship exists between biodiversity and standing biomass. We used hierarchical mixed effects models, based on a power function between species richness and biomass production (Y = a × S^b), and a database of 374 published experiments to estimate the BEF relationship (the change in biomass with the addition of species), and its associated uncertainty, in the context of environmental factors. We found that the mean relationship (b = 0.26, 95% CI: 0.16, 0.37) characterized the vast majority of observations, was robust to differences in experimental design, and was independent of the range of species richness levels considered. However, the richness–biomass relationship varied by trophic level and among ecosystems; in aquatic systems b was nearly twice as large for consumers (herbivores and detritivores) compared to primary producers; in terrestrial ecosystems, b for detritivores was negative but depended on few studies. We estimated changes in biomass expected for a range of changes in species richness, highlighting that species loss has greater implications than species gains, skewing a distribution of biomass change relative to observed species richness change. When biomass provides a good proxy for processes that underpin ecosystem services, this relationship could be used as a step in modeling the production of ecosystem services and their dependence on biodiversity.     

Effects of diversity loss on ecosystem function across trophic levels and ecosystems: A test in a detritus‐based tropical food web

Abstract We investigated the effects of biodiversity loss across trophic levels and across ecosystems (terrestrial to aquatic) on ecosystem function, in a detritus‐based tropical food web. Diversities of consumers (stream shredders) and resources (leaf litter) were experimentally manipulated by varying the number of species from 3 to 1, using different species combinations, and the effects on leaf breakdown rates were examined. In single‐species shredder treatments, leaf diversity loss affected breakdown rates, but the effect depended on the identity of the leaves remaining in the system: they increased when the most preferred leaf species remained, but decreased when this species was lost (leaf preferences were the same for all shredders). In multi‐species shredder assemblages, breakdown rates were lower than expected from single‐species treatments, suggesting an important role of interspecific competition. This pattern was also evident when oneleaf species was available but not with higher leaf diversity, suggesting that lowered leaf diversity promotes competitive interactions among shredders. The influence of diversity and identity of species across trophic levels and ecosystems on stream functioning points to complex interactions that may well be reflected in other types of ecosystem.     

A cross‐system meta‐analysis reveals coupled predation effects on prey biomass and diversity

Predator diversity and abundance are under strong human pressure in all types of ecosystems. Whereas predator potentially control standing biomass and species interactions in food webs, their effects on prey biomass and especially prey biodiversity have not yet been systematically quantified. Here, we test the effects of predation in a cross‐system meta‐analysis of prey diversity and biomass responses to local manipulation of predator presence. We found 291 predator removal experiments from 87 studies assessing both diversity and biomass responses. Across ecosystem types, predator presence significantly decreased both biomass and diversity of prey across ecosystems. Predation effects were highly similar between ecosystem types, whereas previous studies had shown that herbivory or decomposition effects differed fundamentally between terrestrial and aquatic systems based on different stoichiometry of plant material. Such stoichiometric differences between systems are unlikely for carnivorous predators, where effect sizes on species richness strongly correlated to effect sizes on biomass. However, the negative predation effect on prey biomass was ameliorated significantly with increasing prey richness and increasing species richness of the manipulated predator assemblage. Moreover, with increasing richness of the predator assemblage present, the overall negative effects of predation on prey richness switched to positive effects. Our meta‐analysis revealed strong general relationships between predator diversity, prey diversity and the interaction strength between trophic levels in terms of biomass. This study indicates that anthropogenic changes in predator abundance and diversity will potentially have strong effects on trophic interactions across ecosystems. Synthesis The past centuries we have experienced a dramatic loss of top–predator abundance and diversity in most types of ecosystems. To understand the direct consequences of predator loss on a global scale, we quantitatively summarized experiments testing predation effects on prey communities in a cross‐system meta‐analysis. Across ecosystem types, predator presence significantly decreased both biomass and diversity of prey, and predation effects were highly similar. However, with increasing predator richness, the overall negative effects of predation on prey richness switched to positive ones. Anthropogenic changes in predator communities will potentially have strong effects on prey diversity, biomass, and trophic interactions across ecosystems.     

Effects of experimental warming on biodiversity depend on ecosystem type and local species composition

Climatic warming is a primary driver of change in ecosystems worldwide. Here, we synthesize responses of species richness and evenness from 187 experimental warming studies in a quantitative meta‐analysis. We asked 1) whether effects of warming on diversity were detectable and consistent across terrestrial, freshwater and marine ecosystems, 2) if effects on diversity correlated with intensity, duration, and experimental unit size of temperature change manipulations, and 3) whether these experimental effects on diversity interacted with ecosystem types. Using multilevel mixed linear models and model averaging, we also tested the relative importance of variables that described uncontrolled environmental variation and attributes of experimental units. Overall, experimental warming reduced richness across ecosystems (mean log‐response ratio = –0.091, 95% bootstrapped CI: –0.13, –0.05) representing an 8.9% decline relative to ambient temperature treatments. Richness did not change in response to warming in freshwater systems, but was more strongly negative in terrestrial (–11.8%) and marine (–10.5%) experiments. In contrast, warming impacts on evenness were neutral overall and in aquatic systems, but weakly negative on land (7.6%). Intensity and duration of experimental warming did not explain variation in diversity responses, but negative effects on richness were stronger in smaller experimental units, particularly in marine systems. Model‐averaged parameter estimation confirmed these main effects while accounting for variation in latitude, ambient temperature at the sites of manipulations, venue (field versus lab), community trophic type, and whether experiments were open or closed to colonization. These analyses synthesize extensive experimental evidence showing declines in local richness with increased temperature, particularly in terrestrial and marine communities. However, the more variable effects of warming on evenness were better explained by the random effect of site identity, suggesting that effects on species’ relative abundances were contingent on local species composition. Synthesis A global research priority is to understand the consequences of climate change for biodiversity. A growing number of experimental studies have manipulated climatic drivers, in particular changes in temperature, in local communities. In the first quantitative meta‐analysis of community‐level studies across freshwater, marine and terrestrial experiments, species richness declined consistently with experimental warming. This effect was insensitive to warming intensity, duration, and multiple environmental and procedural covariates. However, evenness responses were weakly negative only in terrestrial systems and more variable across ecosystem types. Linear mixed model analyses revealed that the identity of local sites explained nearly 50% of variance in evenness effect sizes, compared to only 10% for richness. This result provides evidence that local species composition strongly constrains changes in relative species abundances in response to warming.     

Biodiversity as a solution to mitigate climate change impacts on the functioning of forest ecosystems

Forest ecosystems are critical to mitigating greenhouse gas emissions through carbon sequestration. However, climate change has affected forest ecosystem functioning in both negative and positive ways, and has led to shifts in species/functional diversity and losses in plant species diversity which may impair the positive effects of diversity on ecosystem functioning. Biodiversity may mitigate climate change impacts on (I) biodiversity itself, as more‐diverse systems could be more resilient to climate change impacts, and (II) ecosystem functioning through the positive relationship between diversity and ecosystem functioning. By surveying the literature, we examined how climate change has affected forest ecosystem functioning and plant diversity. Based on the biodiversity effects on ecosystem functioning (B→EF), we specifically address the potential for biodiversity to mitigate climate change impacts on forest ecosystem functioning. For this purpose, we formulate a concept whereby biodiversity may reduce the negative impacts or enhance the positive impacts of climate change on ecosystem functioning. Further B→EF studies on climate change in natural forests are encouraged to elucidate how biodiversity might influence ecosystem functioning. This may be achieved through the detailed scrutiny of large spatial/long temporal scale data sets, such as long‐term forest inventories. Forest management strategies based on B→EF have strong potential for augmenting the effectiveness of the roles of forests in the mitigation of climate change impacts on ecosystem functioning.     

Species richness and trophic diversity increase decomposition in a co-evolved food web

Ecological communities show great variation in species richness, composition and food web structure across similar and diverse ecosystems. Knowledge of how this biodiversity relates to ecosystem functioning is important for understanding the maintenance of diversity and the potential effects of species losses and gains on ecosystems. While research often focuses on how variation in species richness influences ecosystem processes, assessing species richness in a food web context can provide further insight into the relationship between diversity and ecosystem functioning and elucidate potential mechanisms underpinning this relationship. Here, we assessed how species richness and trophic diversity affect decomposition rates in a complete aquatic food web: the five trophic level web that occurs within water-filled leaves of the northern pitcher plant, Sarracenia purpurea. We identified a trophic cascade in which top-predators--larvae of the pitcher-plant mosquito--indirectly increased bacterial decomposition by preying on bactivorous protozoa. Our data also revealed a facultative relationship in which larvae of the pitcher-plant midge increased bacterial decomposition by shredding detritus. These important interactions occur only in food webs with high trophic diversity, which in turn only occur in food webs with high species richness. We show that species richness and trophic diversity underlie strong linkages between food web structure and dynamics that influence ecosystem functioning. The importance of trophic diversity and species interactions in determining how biodiversity relates to ecosystem functioning suggests that simply focusing on species richness does not give a complete picture as to how ecosystems may change with the loss or gain of species.     

The underappreciated role of life history in mediating the functional consequences of biodiversity change

Biodiversity is changing on both global and local scales, motivating research to understand the consequences of these changes for how communities and ecosystems function. Here, we explore the role of life history strategies in mediating biodiversity and ecosystem functioning. In particular, we evaluate how the composition, biomass (% cover), and richness of perennial (persistence ≥ 1 year) and ephemeral (persistence < 1 year) species change along a gradient of increasing seaweed species richness on a rocky shoreline. We show that the majority of biomass is comprised of perennial species, especially where overall richness is low, whereas the majority of species are ephemeral, especially where overall richness is high. We then present and discuss the results of an 18‐month field manipulation quantifying the factorial effects of tidal elevation, wave exposure, herbivore removals, thermal and desiccation stress amelioration, and nutrient additions on perennial versus ephemeral species. In particular, the diversity of ephemeral species was strongly affected, relative to perennial species, by tidal elevation, wave exposure, and herbivory; herbivores reduced diversity of ephemeral species relative to perennials. Relative to perennial cover, ephemeral cover was greater higher on the shore, in more wave‐exposed habitats, and where herbivores were removed, plots were unscreened, and/or nutrients were added. Thus, perennials and ephemerals responded differently to environmental context and experimental manipulation. We compared nitrate uptake and photosynthesis rates of ephemeral and perennial species and found that maximum nitrate uptake and photosynthesis rates of ephemerals were twice as high as those of perennials. These results highlight the disproportionate roles that ephemeral species play in mediating ecosystem‐level processes. In combination with our comparisons of the diversity and cover of perennial and ephemeral species along a biodiversity gradient, these results demonstrate the utility of incorporating life history traits into our efforts to understand the functional consequences of biodiversity change.     

The relationship between biodiversity and ecosystem functioning in food webs

Recent theoretical and experimental work provides clear evidence that biodiversity loss can have profound impacts on functioning of natural and managed ecosystems and the ability of ecosystems to deliver ecological services to human societies. Work on simplified ecosystems in which the diversity of a single trophic level is manipulated shows that diversity can enhance ecosystem processes such as primary productivity and nutrient retention. Theory also strongly suggests that biodiversity can act as biological insurance against potential disruptions caused by environmental changes. However, these studies generally concern a single trophic level, primary producers for the most part. Changes in biodiversity also affect ecosystem functioning through trophic interactions. Here we review, through the analysis of a simple ecosystem model, several key aspects inherent in multitrophic systems that may strongly affect the relationship between diversity and ecosystem processes. Our analysis shows that trophic interactions have a strong impact on the relationships between diversity and ecosystem functioning, whether the ecosystem property considered is total biomass or temporal variability of biomass at the various trophic levels. In both cases, food-web structure and trade-offs that affect interaction strength have major effects on these relationships. Multitrophic interactions are expected to make biodiversity–ecosystem functioning relationships more complex and non-linear, in contrast to the monotonic changes predicted for simplified systems with a single trophic level.     

青藏高原高寒草地生物多样性与生态系统功能的关系

生物多样性和生态系统功能(BEF)之间的关系是目前陆地生态系统生态学研究的热点, 对于生态系统的高效利用与管理意义重大, 而且对于退化生态系统功能的恢复及生物多样性的保护有重要的指导作用。高寒草地是青藏高原生态系统的主体, 近年来, 在气候变化与人为干扰等因素的驱动下, 高寒草地生态系统功能严重衰退。为此, 本文在综述物种多样性和生态系统功能及其相互关系研究进展的基础上, 首先从地下生态学过程研究、全球变化对生态系统多功能性的影响等方面解析了目前关于草地生物多样性和生态系统功能研究中存在的问题。继而, 从不同草地类型、草地退化程度、放牧、模拟气候变化、刈割、施肥、封育和补播等干扰利用方式对高寒草地物种多样性与生态系统功能的影响进行了全面的评述。并指出了高寒草地BEF研究中存在的不足, 今后应基于物种功能多样性开展高寒草地BEF研究, 全面且综合地考虑非生物因子(养分资源、外界干扰、环境波动等)对生物多样性与生态系统功能之间关系的影响, 关注尺度效应和要素耦合在全球气候变化对高寒草地BEF研究中的作用。最后, 以高寒草地BEF研究进展和结论为支撑依据, 综合提出了高寒草地资源利用和生物多样性保护的措施与建议: 加强放牧管理, 保护生物多样性; 治理退化草地, 维持生物多样性功能; 加强创新保护理念, 增强生态系统功能。     

Integrating methods that investigate how complementarity influences ecosystem functioning

Separating the mechanisms that influence ecosystem functioning has been a goal of recent high profile experiments. Integrating the various experimental and analytical methods that attempt this goal across terrestrial and aquatic ecosystems, as well as careful definition of 'complementarity', produces novel insights and valuable lessons about new directions for research. (1) Experimental designs differ in temporal scale and whether standing stock or another ecosystem process was the response variable. (2) Mathematically identical variables in different designs have contrasting ecological interpretations. For example, different sets of ecological processes can contribute to different variables in different experimental designs. (3) The frequency of transgressive overyielding of standing stock (e.g. total above ground biomass) in polycultures implies little about the prevalence of transgressive overyielding in other ecosystem processes. (4) Measuring the contribution to ecosystem functioning of individual species, rather than just total ecosystem functioning of a polyculture, is not essential for estimating effects of complementarity. (5) Further research will profit from distinguishing standing stock from all other ecosystem functions. (6) None of the analytic methods can distinguish the effects of individual processes or mechanisms such as resource use differentiation, facilitation, or allelopathy, for which additional experimental treatments are required.     

Regional zooplankton biodiversity provides limited buffering of pond ecosystems against climate change

1. Climate change and other human-driven environmental perturbations are causing reductions in biodiversity and impacting the functioning of ecosystems on a global scale. Metacommunity theory suggests that ecosystem connectivity may reduce the magnitude of these impacts if the regional species pool contains functionally redundant species that differ in their environmental tolerances. Dispersal may increase the resistance of local ecosystems to environmental stress by providing regional species with traits adapted to novel conditions. 2. We tested this theory by subjecting freshwater zooplankton communities in mesocosms that were either connected to or isolated from the larger regional species pool to a factorial manipulation of experimental warming and increased salinity. 3. Compensation by regional taxa depended on the source of stress. Warming tolerant regional taxa partially compensated for reductions in heat sensitive local taxa but similar compensation did not occur under increased salinity. 4. Dispersal-mediated species invasions dampened the effects of warming on summer net ecosystem productivity. However, this buffering effect did not occur in the fall or for periphyton growth, the only other ecosystem function affected by the stress treatments. 5. The results indicate that regional biodiversity can provide insurance in a dynamic environment but that the buffering capacity is limited to some ecosystem processes and sources of stress. Maintaining regional biodiversity and habitat connectivity may therefore provide some limited insurance for local ecosystems in changing environments, but is unable to impart resistance against all sources of environmental stress.     

A synthesis of subdisciplines: predator–prey interactions, and biodiversity and ecosystem functioning

The last 15 years has seen parallel surges of interest in two research areas that have rarely intersected: biodiversity and ecosystem functioning (BEF), and multispecies predator–prey interactions (PPI). Research addressing role of biodiversity in ecosystem functioning has focused primarily on single trophic‐level systems, emphasizing additive effects of diversity that manifest through resource partitioning and the sampling effect. Conversely, research addressing predator–prey interactions has focused on two trophic‐level systems, emphasizing indirect and non‐additive interactions among species. Here, we use a suite of consumer‐resource models to organize and synthesize the ways in which consumer species diversity affects the densities of both resources and consumer species. Specifically, we consider sampling effects, resource partitioning, indirect effects caused by intraguild interactions and non‐additive effects. We show that the relationship between consumer diversity and the density of resources and consumer species are broadly similar for systems with one vs. two trophic levels, and that indirect and non‐additive interactions generally do little more than modify the impacts of diversity established by the sampling effect and resource partitioning. The broad similarities between systems with one vs. two trophic levels argue for greater communication between researchers studying BEF, and researchers studying multispecies PPI.     

陆地生态系统植物多样性对矿质元素输入的响应

人类活动的加剧改变了陆地生态系统矿质元素(如氮、磷、钾等)循环的速度和方向,并且对生态系统的结构和功能也产生重要影响。如今,矿质元素输入量的改变及其产生的后续效应对陆地生态系统生物多样性的影响备受学者们的关注。从4个方面综述了全球氮沉降背景下主要矿质元素输入的改变对陆地植物多样性的影响及其机理:1)矿质营养元素限制的概念、确定方法以及与植物多样性的耦合关系;2)概述了氮、磷、钾等主要矿质元素输入对陆地植物多样性的影响:主要表现为负面效应;3)探讨了矿质元素输入影响植物多样性的可能机制,包括生态系统水平上的机制(如竞争排斥、酸化铝毒、物种入侵、同质性假说,间接诱导机制等)和植物个体水平上的机制(如元素失衡和环境敏感性增加等);4)根据目前研究现状,指出了已有研究的局限性,分析了未来可能的研究方向和重点。