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Plant diversity can increase biomass production in plot-scale studies, but applying these results to ecosystem carbon (C) storage at larger spatial and temporal scales remains problematic. Other ecosystem controls interact with diversity and plant production, and may influence soil pools differently from plant pools. We integrated diversity with the state-factor framework, which identifies key controls, or 'state factors', over ecosystem properties and services such as C storage. We used this framework to assess the effects of diversity, plant traits and state factors (climate, topography, time) on live tree, standing dead, organic horizon and total C in Québec forests. Four patterns emerged: (1) while state factors were usually the most important model predictors, models with both state and biotic factors (mean plant traits and diversity) better predicted C pools; (2) mean plant traits were better predictors than diversity; (3) diversity increased live tree C but reduced organic horizon C; (4) different C pools responded to different traits and diversity metrics. These results suggest that, where ecosystem properties result from multiple processes, no simple relationship may exist with any one organismal factor. Integrating biodiversity into ecosystem ecology and assessing both traits and diversity improves our mechanistic understanding of biotic effects on ecosystems.

International audience; Global species extinction rates are orders of magnitude above the background rate documented in the fossil record. However, recent data syntheses have found mixed evidence for patterns of net species loss at local spatial scales. For example, two recent data meta-analyses have found that species richness is decreasing in some locations and is increasing in others. When these trends are combined, these papers argued there has been no net change in species richness, and suggested this pattern is globally representative of biodiversity change at local scales. Here we reanalyze results of these data syntheses and outline why this conclusion is unfounded. First, we show the datasets collated for these syntheses are spatially biased and not representative of the spatial distribution of species richness or the distribution of many primary drivers of biodiversity change. This casts doubt that their results are representative of global patterns. Second, we argue that detecting the trend in local species richness is very difficult with short time series and can lead to biased estimates of change. Reanalyses of the data detected a signal of study duration on biodiversity change, indicating net biodiversity loss is most apparent in studies of longer duration. Third, estimates of species richness change can be biased if species gains during post-disturbance recovery are included without also including species losses that occurred during the disturbance. Net species gains or losses should be assessed with respect to common baselines or reference communities. Ultimately, we need a globally coordinated effort to monitor biodiversity so that we can estimate and attribute human impacts as causes of biodiversity change. A combination of technologies will be needed to produce regularly updated global datasets of local biodiversity change to guide future policy. At this time the conclusion that there is no net change in local species richness is not the consensus state of knowledge.

Biodiversity confers economic value by enhancing carbon storage in grasslands, an economic argument for biodiversity conservation., Carbon storage by ecosystems is valuable for climate protection. Biodiversity conservation may help increase carbon storage, but the value of this influence has been difficult to assess. We use plant, soil, and ecosystem carbon storage data from two grassland biodiversity experiments to show that greater species richness increases economic value: Increasing species richness from 1 to 10 had twice the economic value of increasing species richness from 1 to 2. The marginal value of each additional species declined as species accumulated, reflecting the nonlinear relationship between species richness and plant biomass production. Our demonstration of the economic value of biodiversity for enhancing carbon storage provides a foundation for assessing the value of biodiversity for decisions about land management. Combining carbon storage with other ecosystem services affected by biodiversity may well enhance the economic arguments for conservation even further.

Evidence is mounting that extinctions are altering key processes important to the productivity and sustainability of Earth’s ecosystems 1–4 . Further species loss will accelerate change in ecosystem processes 5–8 , but it is unclear how these effects compare to the direct effects of other forms of environmental change that are both driving diversity loss and altering ecosystem function. Here we use a suite of meta-analyses of published data to show that the effects of species loss on productivity and decomposition—two processes important in all ecosystems—are of comparable magnitude to the effects of many other global environmental changes. In experiments, intermediate levels of species loss (21–40%) reduced plant production by 5–10%, comparable to previously documented effects of ultraviolet radiation and climate warming. Higher levels of extinction (41–60%) had effects rivalling those of ozone, acidification, elevated CO2 and nutrient pollution. At intermediate levels, species loss generally had equal or greater effects on decomposition than did elevated CO2 and nitrogen addition. The identity of species lost also had a large effect on changes in productivity and decomposition, generating a wide range of plausible outcomes for extinction. Despite the need for more studies on interactive effects of diversity loss and environmental changes, our analyses clearly show that the ecosystem consequences of local species loss are as quantitatively significant as the direct effects of several global change stressors that have mobilized major international concern and remediation efforts 9 .

Over the past several decades, a rapidly expanding field of research known as biodiversity and ecosystem functioning has begun to quantify how the world's biological diversity can, as an independent variable, control ecological processes that are both essential for, and fundamental to, the functioning of ecosystems. Research in this area has often been justified on grounds that (1) loss of biological diversity ranks among the most pronounced changes to the global environment and that (2) reductions in diversity, and corresponding changes in species composition, could alter important services that ecosystems provide to humanity (e.g., food production, pest/disease control, water purification). Here we review over two decades of experiments that have examined how species richness of primary producers influences the suite of ecological processes that are controlled by plants and algae in terrestrial, marine, and freshwater ecosystems. Using formal meta-analyses, we assess the balance of evidence for eight fundamental questions and corresponding hypotheses about the functional role of producer diversity in ecosystems. These include questions about how primary producer diversity influences the efficiency of resource use and biomass production in ecosystems, how primary producer diversity influences the transfer and recycling of biomass to other trophic groups in a food web, and the number of species and spatial /temporal scales at which diversity effects are most apparent. After summarizing the balance of evidence and stating our own confidence in the conclusions, we outline several new questions that must now be addressed if this field is going to evolve into a predictive science that can help conserve and manage ecological processes in ecosystems.

Summary 1. Recent debates about the role of biotic resistance in controlling invasion success have focused on effects of species richness. However, functional composition could be a stronger control: species already in the community with similar functional traits to those of the invaders should have the greatest competitive effect on invaders. Still, experiments assessing effects of functional similarity have found contradictory results. 2. We used experimental communities in a serpentine grassland in California, USA, to assess the extent to which functional composition and functional diversity influenced success of two different types of invading plants: early season annuals (E) and late-season annuals (L) that have been previously shown to differ in patterns of resource acquisition. 3. We seeded known quantities of seed of six different species (three in each functional group) into experimental plots containing established communities differing in functional composition and functional diversity. The experimental communities contained different combinations of E, L, perennial bunchgrass (P) and nitrogen-fixer (N) functional groups, with functional diversity ranging from 0 to 4 groups. Each invading species was seeded into a separate quadrat within each plot to minimize competitive effects of invaders on each other. We measured both seedling and adult success of invaders for two full growing seasons to further understand mechanisms underlying biotic resistance. 4. More functionally diverse communities were less invaded overall, as measured by the average success of individual invaders. However, assessment of invaders by functional groups was more informative: Es in the extant community suppressed E invaders the most, and Ls in the extant community suppressed L invaders the most. 5. We observed a variety of interactions among extant functional groups in reducing invader success, including synergism, complementarity and ‘basement’ effects, where two or more groups negatively affected invaders, but combinations of groups were no more suppressive than single groups. The extant community influenced invaders more strongly through suppression of adult plant growth than through effects on seedling establishment. 6. Synthesis. Contrary to predictions from neutral theory, these results indicate that niche overlap was an important component of biotic resistance in these experimental plant communities and summed up to significant effects of species richness.

A recent debate among ecologists has focused on mechanisms by which species diversity might affect net primary productivity. Communities with more species could use a greater variety of resource capture characteristics, leading to greater use of limiting resources (complementarity) and therefore greater productivity (overyielding). Recent experiments, however, have shown a variety of relationships between diversity and productivity. In an experiment on serpentine grassland communities spanning 8 years, we found that overyielding increased several years after plot establishment. Overyielding varied greatly depending on the functional characteristics of the species involved and the biotic and abiotic environment (particularly water availability). While functional differences among species led to strong complementarity and facilitation, these effects were not sufficient to cause significant transgressive overyielding or consistent increases in productivity with increased plant diversity. These results suggest that greater absolute production with greater diversity may be restricted to particular species combinations or environmental conditions.

The ecological consequences of biodiversity loss have aroused considerable interest and controversy during the past decade. Major advances have been made in describing the relationship between species diversity and ecosystem processes, in identifying functionally important species, and in revealing underlying mechanisms. There is, however, uncertainty as to how results obtained in recent experiments scale up to landscape and regional levels and generalize across ecosystem types and processes. Larger numbers of species are probably needed to reduce temporal variability in ecosystem processes in changing environments. A major future challenge is to determine how biodiversity dynamics, ecosystem processes, and abiotic factors interact.

F. Stuart Chapin (e-mail: fschapin@socrates. berkeley.edu) is a professor and David U. Hooper is a postdoctoral fellow in the Department of Integrative Biology, University of California, Berkeley, CA 94720. Osvaldo E. Sala is a professor at the Faculty of Agronomy, University of Buenos Aires, Av. San Martin 4453, Buenos Aires 1417, Argentina. Ingrid C. Burke is an associate professor in the Department of Forest Sciences, Colorado State University, Ft. Collins, CO 80523. J. Phillip Grime is a professor in the Unit of Comparative Plant Ecology, The University of Sheffield, Sheffield S10 2TN, UK. William K. Lauenroth is a professor in the Rangeland Ecosystem Science Department, Natural Resource Ecology Laboratory, Colorado State University, Ft. Collins, CO 80523. Amanda Lombard is a research scientist at the FitzPatrick Institute, University of Cape Town, Cape Town, 7700 South Africa. Harold A. Mooney is a professor in the Department of Biological Sciences, Stanford University, Stanford, CA 94305. Arvin R. Mosier is a research scientist in the USDA Agricultural Research Service, P. O. Box E, Ft. Collins, CO 80522. Shahid Naeem is an assistant professor and David Tilman is a professor in the Department of Ecology, Evolution, and Behavior, University of Minnesota, St. Paul, MN 55108. Stephen W. Pacala is a professor in the Department of Ecology and Evolutionary Biology, Princeton University, Princeton, NJ 08544. Jacques Roy is director of research at the Centre d'Ecologie Fonctionnelle et Evolutive, CNRS, F-34293 Montpellier Cedex 5, France. William L. Steffen is executive officer of GCTE, CSIRO, Division of Wildlife and Ecology, Lyneham ACT 2602, Australia. Changes in biodiversity can have significant

Extensive research shows that more species-rich assemblages are generally more productive and efficient in resource use than comparable assemblages with fewer species. But the question of how diversity simultaneously affects the wide variety of ecological functions that ecosystems perform remains relatively understudied, and it presents several analytical and empirical challenges that remain unresolved. In particular, researchers have developed several disparate metrics to quantify multifunctionality, each characterizing different aspects of the concept, and each with pros and cons. We compare four approaches to characterizing multifunctionality and its dependence on biodiversity, quantifying 1) magnitudes of multiple individual functions separately, 2) the extent to which different species promote different functions, 3) the average level of a suite of functions, and 4) the number of functions that simultaneously exceed a critical threshold. We illustrate each approach using data from the pan-European BIODEPTH experiment and the R multifunc package developed for this purpose, evaluate the strengths and weaknesses of each approach, and implement several methodological improvements. We conclude that a extension of the fourth approach that systematically explores all possible threshold values provides the most comprehensive description of multifunctionality to date. We outline this method and recommend its use in future research., Comment: This article has been submitted to Methods in Ecology & Evolution for review

The most unique feature of Earth is the existence of life, and the most extraordinary feature of life is its diversity. Approximately 9 million types of plants, animals, protists and fungi inhabit the Earth. So, too, do 7 billion people. Two decades ago, at the first Earth Summit, the vast majority of the world's nations declared that human actions were dismantling the Earth's ecosystems, eliminating genes, species and biological traits at an alarming rate. This observation led to the question of how such loss of biological diversity will alter the functioning of ecosystems and their ability to provide society with the goods and services needed to prosper.

Human alteration of the global environment has triggered the sixth major extinction event in the history of life and caused widespread changes in the global distribution of organisms. These changes in biodiversity alter ecosystem processes and change the resilience of ecosystems to environmental change. This has profound consequences for services that humans derive from ecosystems. The large ecological and societal consequences of changing biodiversity should be minimized to preserve options for future solutions to global environmental problems. Fil: Chapin III, F. Stuart. University Of Alaska; Estados Unidos Fil: Zavaleta, Erika S.. University of Stanford; Estados Unidos Fil: Eviner, Valerie T.. University of California at Berkeley; Estados Unidos Fil: Naylor, Rosamond L.. University of Stanford; Estados Unidos Fil: Vitousek, Peter M.. University of Stanford; Estados Unidos Fil: Reynolds, Heather L.. Kalamazoo College; Estados Unidos Fil: Hooper, David U.. Western Washington University; Estados Unidos Fil: Lavorel, Sandra. Centre National de la Recherche Scientifique; Francia Fil: Sala, Osvaldo Esteban. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Instituto de Investigaciones Fisiológicas y Ecológicas Vinculadas a la Agricultura. Universidad de Buenos Aires. Facultad de Agronomía. Instituto de Investigaciones Fisiológicas y Ecológicas Vinculadas a la Agricultura; Argentina Fil: Hobbie, Sarah E.. University of Minnesota; Estados Unidos Fil: Mack, Michelle C.. University Of Alaska; Estados Unidos Fil: Díaz, Sandra Myrna. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto Multidisciplinario de Biología Vegetal. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas Físicas y Naturales. Instituto Multidisciplinario de Biología Vegetal; Argentina

Nature 486, 59–67 (2012); doi:10.1038/nature11148 In Table 1 and Supplementary Table 2 of this Review, under the ‘Category of service’ called ‘Regulating’, the first two ‘Measures of service provision’ related to ‘Biocontrol’ should read ‘Abundance of herbivorous pests’ instead of ‘Control of herbivorous pests’.

The effect of biological diversity on ecosystem biogeochemistry has not been widely studied in recent years, due in part to widespread recognition that our understanding of population/ecosystem interactions was insufficient to sustain the pioneering discussions of the late 1960s (cf. Woodwell and Smith 1969). Indeed, the fields of population biology and ecosystem studies largely pursued different approaches throughout much of the 1970s and 1980s. The gap between population and ecosystem ecology is now narrowing substantially, and the linked nature of human alterations to both biological diversity and ecosystem functioning is increasingly appreciated. These developments have led to renewed interest in the connections between diversity and many aspects of ecosystem function.

Assistant professor in the Department of Biology at Western Washington University, Bellingham, Washington 98225-9160 10: Professor at the Laboratoire d'Ecologie de Sols Tropicaux, ORSTOM/Universite Paris VI, 32 Avenue Henri Varagnat, 93143 Bondy, France 11: Senior scientist at the Centre for Terrestrial Ecology, Netherlands Institute of Ecology, 6666 ZG Heteren, Netherlands Utrecht, Netherlands 12: Professor at the Department of Environmental Studies, University of Utrecht, Utrecht, Netherlands 13: Professor at the Institute of Soil Biology, Academy of Sciences of the Czech Republic, Na sadkach 7, 370 05 Ceske Budejovice, Czech Republic 14: Professor at the Department of Environmental Science, Policy,and Management, University of California, Berkeley, California 94720-3110 15: Professor at the Center for Microbial Ecology, Michigan State University, 540 Plant and Soil Science Building, East Lansing, Michigan 48824-1325 16: Professor at the Department of Animal Ecology, Justus Liebig University of Giessen, Heinrich-Buff-Ring 26-32 (IFZ), D-35392 Giessen, Germany 2: Professor at the Queen Mary and Westfield College, School of Biological Sciences, University of London, London E1 4NS, United Kingdom 3: Research professor and the director of the Centre for Agri-Environmental Research, Department of Agriculture, University of Reading, Earley Gate, Reading RG6 6AT, United Kingdom 4: Professor of Soil Biology and Biological Soil Quality and director of the Department of Environmental Sciences, Wageningen University, 6700 EC Wageningen, Netherlands 5: Professor at the Centre for Biodiversity and Bioresources, School of Biological Sciences, Macquarie University, Sydney, New South Wales 2109, Australia 6: Chair, SCOPE Committee on Soil and Sediment Biodiversity and Ecosystem Functioning, and professor and director, Natural Resource Ecology Laboratory, Colorado State University, Fort Collins, Colorado 80523 7: Scientist at Landcare Research, Lincoln, New Zealand 8: Research professor in the Institute of Ecology at the University of Georgia, 102 Ecology Annex, Athens, Georgia 30602-2360 9: Professor at the Department of Soil Science and Agricultural Engineering, University of Zimbabwe, Mount Pleasant, Harare, Zimbabwe