The value of biodiversity experiments

Summary Recent biodiversity experiments have investigated the relationship between diversity and ecosystem functioning by synthesizing plant communities from pools of species that have been experimentally manipulated to vary numbers and types of species present while holding abiotic factors constant. Biodiversity experiments therefore focus on a previously under-explored aspect of global change: the feedback from diversity to environment. Consequences of random manipulation of species communities may not correspond well to those of specific extinction sequences observed in the past in response to extinction drivers that cause highly non-random loss. However, random manipulation provides a good starting point given that existing communities could undergo many alternative orders of species loss in the future in response to a variety of different potential extinction drivers. Further, the effects of some extinction drivers are currently poorly understood and therefore difficult to predict (e.g. climate change) and it may be premature to dismiss the predictions of random scenarios as irrelevant to all real examples of species loss. The first generations of biodiversity experiments have provided valuable, and sometimes unexpected, discoveries about the general nature of the relationship between diversity and ecosystem functioning. These discoveries could not have been made using observational studies. We propose that different examples of extinction loss in the real or a potential future world form a continuum from situations where the results of the first-generation biodiversity experiments will be highly relevant to less relevant. At the one extreme are examples where the effects of biodiversity on ecosystem functioning will be overwhelmed by direct effects of the extinction driver on processes (e.g. chronic eutrophication). At the other extreme are situations where ecosystem processes are not strongly affected by direct effects of the extinction driver and where the effects of species loss on functioning may be more important (e.g. habitat fragmentation). Given the unprecedented uncertainty about the future of biodiversity and the functioning of ecosystems, a general approach with randomly varying species pools was the right place to start in order to provide a general foundation. The new challenge is to test for effects of biodiversity on functioning in real-world examples of species loss.

[1]  D. H. Knight,et al.  Aims and Methods of Vegetation Ecology , 1974 .

[2]  F. Bazzaz,et al.  Interactive effects of diversity, nutrients and elevated CO2 on experimental plant communities , 2002 .

[3]  P. Reich,et al.  [Letters to nature] , 1975, Nature.

[4]  R. Levins.  Evolution in Changing Environments , 1968 .

[5]  L. Aarssen.  On correlations and causations between productivity and species richness in vegetation: predictions from habitat attributes , 2001 .

[6]  M. Loreau,et al.  Biodiversity and ecosystem functioning : synthesis and perspectives , 2002 .

[7]  Jason D. Fridley,et al.  Resource availability dominates and alters the relationship between species diversity and ecosystem productivity in experimental plant communities , 2002, Oecologia.

[8]  Andrew Gonzalez,et al.  Heterotroph species extinction, abundance and biomass dynamics in an experimentally fragmented microecosystem , 2002 .

[9]  Ruprecht Düll,et al.  Zeigerwerte von Pflanzen in Mitteleuropa , 1992 .

[10]  J. P. Grime,et al.  Biodiversity and Ecosystem Functioning: Current Knowledge and Future Challenges , 2001, Science.

[11]  Jan Lepš,et al.  What do the biodiversity experiments tell us about consequences of plant species loss in the real world , 2004 .

[12]  M. Fischer,et al.  Local Extinctions of Plants in Remnants of Extensively Used Calcareous Grasslands 1950 –1985 , 1997 .

[13]  J. Roy,et al.  Separating the chance effect from other diversity effects in the functioning of plant communities , 2001 .

[14]  James M. Bullock,et al.  Restoration of biodiversity enhances agricultural production , 2001 .

[15]  B. Schmid,et al.  ECOSYSTEM EFFECTS OF BIODIVERSITY: A CLASSIFICATION OF HYPOTHESES AND EXPLORATION OF EMPIRICAL RESULTS , 1999 .

[16]  F. Berendse,et al.  Positive effects of plant species diversity on productivity in the absence of legumes , 2003 .

[17]  Bernhard Schmid,et al.  Non‐random species extinction and plant production: implications for ecosystem functioning , 2005 .

[18]  Katherine L. Gross,et al.  WHAT IS THE OBSERVED RELATIONSHIP BETWEEN SPECIES RICHNESS AND PRODUCTIVITY , 2001 .

[19]  J. Fridley.  Diversity effects on production in different light and fertility environments: an experiment with communities of annual plants , 2003 .

[20]  P. Dimitrakopoulos,et al.  Biodiversity effects increase linearly with biotope space , 2004 .

[21]  B. Schmid.  The species richness–productivity controversy , 2002 .

[22]  M. Loreau,et al.  Overyielding in grassland communities: testing the sampling effect hypothesis with replicated biodiversity experiments , 2002 .

[23]  Michel Loreau,et al.  Partitioning selection and complementarity in biodiversity experiments , 2001, Nature.

[24]  James B. Grace,et al.  The factors controlling species density in herbaceous plant communities: an assessment , 1999 .

[25]  B. Schmid,et al.  Diversity-dependent production can decrease the stability of ecosystem functioning , 2002, Nature.

[26]  M. Fischer,et al.  Rapid decay of diversity-productivity relationships after invasion of experimental plant communities , 2004 .

[27]  Pereira,et al.  Plant diversity and productivity experiments in european grasslands , 1999, Science.