Plant diversity and productivity experiments in european grasslands
Imperial College London1, University of Zurich2, University of Bayreuth3, Technical University of Lisbon4, University of the Aegean5, University College Cork6, Swedish University of Agricultural Sciences7, University of Basel8, École Normale Supérieure9, University of Sheffield10, Max Planck Society11
05 Nov 1999-Science (American Association for the Advancement of Science)-Vol. 286, Iss: 5442, pp 1123-1127
TL;DR: Niche complementarity and positive species interactions appear to play a role in generating diversity-productivity relationships within sites in addition to sampling from the species pool.
Abstract: At eight European field sites, the impact of loss of plant diversity on primary productivity was simulated by synthesizing grassland communities with different numbers of plant species. Results differed in detail at each location, but there was an overall log-linear reduction of average aboveground biomass with loss of species. For a given number of species, communities with fewer functional groups were less productive. These diversity effects occurred along with differences associated with species composition and geographic location. Niche complementarity and positive species interactions appear to play a role in generating diversity-productivity relationships within sites in addition to sampling from the species pool.
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Western Washington University1, University of Alaska Fairbanks2, United States Forest Service3, University of Zurich4, Centre national de la recherche scientifique5, Natural Environment Research Council6, University of Notre Dame7, École Normale Supérieure8, Columbia University9, University of Helsinki10, United States Geological Survey11, University of Michigan12, Landcare Research13, Swedish University of Agricultural Sciences14
TL;DR: Understanding this complexity, while taking strong steps to minimize current losses of species, is necessary for responsible management of Earth's ecosystems and the diverse biota they contain.
Abstract: Humans are altering the composition of biological communities through a variety of activities that increase rates of species invasions and species extinctions, at all scales, from local to global. These changes in components of the Earth's biodiversity cause concern for ethical and aesthetic reasons, but they also have a strong potential to alter ecosystem properties and the goods and services they provide to humanity. Ecological experiments, observations, and theoretical developments show that ecosystem properties depend greatly on biodiversity in terms of the functional characteristics of organisms present in the ecosystem and the distribution and abundance of those organisms over space and time. Species effects act in concert with the effects of climate, resource availability, and disturbance regimes in influencing ecosystem properties. Human activities can modify all of the above factors; here we focus on modification of these biotic controls. The scientific community has come to a broad consensus on many aspects of the re- lationship between biodiversity and ecosystem functioning, including many points relevant to management of ecosystems. Further progress will require integration of knowledge about biotic and abiotic controls on ecosystem properties, how ecological communities are struc- tured, and the forces driving species extinctions and invasions. To strengthen links to policy and management, we also need to integrate our ecological knowledge with understanding of the social and economic constraints of potential management practices. Understanding this complexity, while taking strong steps to minimize current losses of species, is necessary for responsible management of Earth's ecosystems and the diverse biota they contain.
6,891 citations
Cites background from "Plant diversity and productivity ex..."
...Here, we differentiate managed ecosystems from merely degraded ecosystems (‘‘polluted, overexploited, or converted that have not been managed’’; cf. Silver et al. 2001)....
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...…this consistency of diversity and dominant species’ traits across gradients of nitrogen deposition, the debate about effects of species richness vs. composition in some experiments (Givnish 1994, Tilman and Downing 1994, Huston 1997) may be moot from the perspective of managing nitrogen within…...
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TL;DR: A doubling in global food demand projected for the next 50 years poses huge challenges for the sustainability both of food production and of terrestrial and aquatic ecosystems and the services they provide to society.
Abstract: A doubling in global food demand projected for the next 50 years poses huge challenges for the sustainability both of food production and of terrestrial and aquatic ecosystems and the services they provide to society. Agriculturalists are the principal managers of global useable lands and will shape, perhaps irreversibly, the surface of the Earth in the coming decades. New incentives and policies for ensuring the sustainability of agriculture and ecosystem services will be crucial if we are to meet the demands of improving yields without compromising environmental integrity or public health.
6,569 citations
Cites background from "Plant diversity and productivity ex..."
...Practices that change species composition or reduce biodiversity in non-agricultural systems may also diminish goods and services, because the ability of ecosystems to provide some services depends both on the number and type of species in an ecosyste...
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University of Michigan1, College of William & Mary2, McGill University3, Western Washington University4, Arizona State University5, Imperial College London6, University of Minnesota7, Swedish University of Agricultural Sciences8, Stanford University9, Centre national de la recherche scientifique10, United States Geological Survey11, University of British Columbia12, Columbia University13
TL;DR: It is argued that human actions are dismantling the Earth’s ecosystems, eliminating genes, species and biological traits at an alarming rate, and 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 is asked.
Abstract: 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.
5,244 citations
TL;DR: The nervous system seems to combine visual and haptic information in a fashion that is similar to a maximum-likelihood integrator, and this model behaved very similarly to humans in a visual–haptic task.
Abstract: When a person looks at an object while exploring it with their hand, vision and touch both provide information for estimating the properties of the object. Vision frequently dominates the integrated visual-haptic percept, for example when judging size, shape or position, but in some circumstances the percept is clearly affected by haptics. Here we propose that a general principle, which minimizes variance in the final estimate, determines the degree to which vision or haptics dominates. This principle is realized by using maximum-likelihood estimation to combine the inputs. To investigate cue combination quantitatively, we first measured the variances associated with visual and haptic estimation of height. We then used these measurements to construct a maximum-likelihood integrator. This model behaved very similarly to humans in a visual-haptic task. Thus, the nervous system seems to combine visual and haptic information in a fashion that is similar to a maximum-likelihood integrator. Visual dominance occurs when the variance associated with visual estimation is lower than that associated with haptic estimation.
4,142 citations
TL;DR: Larger numbers of species are probably needed to reduce temporal variability in ecosystem processes in changing environments and to determine how biodiversity dynamics, ecosystem processes, and abiotic factors interact.
Abstract: 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.
4,070 citations
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TL;DR: Functional composition and functional diversity were the principal factors explaining plant productivity, plant percent nitrogen, plant total nitrogen, and light penetration in grassland plots.
Abstract: Humans are modifying both the identities and numbers of species in ecosystems, but the impacts of such changes on ecosystem processes are controversial. Plant species diversity, functional diversity, and functional composition were experimentally varied in grassland plots. Each factor by itself had significant effects on many ecosystem processes, but functional composition and functional diversity were the principal factors explaining plant productivity, plant percent nitrogen, plant total nitrogen, and light penetration. Thus, habitat modifications and management practices that change functional diversity and functional composition are likely to have large impacts on ecosystem processes.
2,762 citations
TL;DR: In this paper, the authors used a well-replicated field experiment, in which species diversity was directly controlled, to show that ecosystem productivity in 147 grassland plots increased significantly with plant biodiversity.
Abstract: THE functioning and sustainability of ecosystems may depend on their biological diversity1–8. Elton's9 hypothesis that more diverse ecosystems are more stable has received much attention1,3,6,7,10–14, but Darwin's proposal6,15 that more diverse plant communities are more productive, and the related conjectures4,5,16,17 that they have lower nutrient losses and more sustainable soils, are less well studied4–6,8,17,18. Here we use a well-replicated field experiment, in which species diversity was directly controlled, to show that ecosystem productivity in 147 grassland plots increased significantly with plant biodiversity. Moreover, the main limiting nutrient, soil mineral nitrogen, was utilized more completely when there was a greater diversity of species, leading to lower leaching loss of nitrogen from these ecosystems. Similarly, in nearby native grassland, plant productivity and soil nitrogen utilization increased with increasing plant species richness. This supports the diversity–productivity and diversity–sustainability hypotheses. Our results demonstrate that the loss of species threatens ecosystem functioning and sustainability.
2,541 citations
TL;DR: In this paper, the authors provide evidence from direct experimental manipulation of diversity by over an order of magnitude, using multi-trophic level communities and simultaneous measures of several ecosystem processes, that reduced biodiversity may indeed alter the performance of ecosystems.
Abstract: COMMUNITIES of species and their associated biological, chemical and physical processes, collectively known as ecosystems, drive the Earth's biogeochemical processes1,2. Currently most ecosystems are experiencing loss of biodiversity associated with the activities of human expansion3–5, raising the issue of whether the biogeochemical functioning of ecosystems will be impaired by this loss of species6–8. Current ecological knowledge supports a wide range of views on the subject9–13, but empirical tests are few9,14–16. Here we provide evidence from direct experimental manipulation of diversity by over an order of magnitude, using multi-trophic level communities and simultaneous measures of several ecosystem processes, that reduced biodiversity may indeed alter the performance of ecosystems.
1,632 citations
TL;DR: Case studies re-evaluating three different types of biodiversity experiments demonstrate that the increases found in such ecosystem properties as productivity, nutrient use efficiency, and stability were actually caused by “hidden treatments” that altered plant biomass and productivity.
Abstract: Interactions between biotic and abiotic pro- cesses complicate the design and interpretation of eco- logical experiments. Separating causality from simple correlation requires distinguishing among experimental treatments, experimental responses, and the many pro- cesses and properties that are correlated with either the treatments or the responses, or both. When an experi- mental manipulation has multiple components, but only one of them is identified as the experimental treatment, erroneous conclusions about cause and eAect relation- ships are likely because the actual cause of any observed response may be ignored in the interpretation of the experimental results. This unrecognized cause of an observed response can be considered a ''hidden treat- ment.'' Three types of hidden treatments are potential problems in biodiversity experiments: (1) abiotic condi- tions, such as resource levels, or biotic conditions, such as predation, which are intentionally or unintentionally altered in order to create diAerences in species numbers for ''diversity'' treatments; (2) non-random selection of species with particular attributes that produce treatment diAerences that exceed those due to ''diversity'' alone; and (3) the increased statistical probability of including a species with a dominant negative or positive eAect (e.g., dense shade, or nitrogen fixation) in randomly selected groups of species of increasing number or ''diversity.'' In each of these cases, treatment responses that are actually the result of the ''hidden treatment'' may be inadver- tently attributed to variation in species diversity. Case studies re-evaluating three diAerent types of biodiversity experiments demonstrate that the increases found in such ecosystem properties as productivity, nutrient use eAciency, and stability (all of which were attributed to higher levels of species diversity) were actually caused by ''hidden treatments'' that altered plant biomass and productivity.
1,601 citations