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Proc Natl Acad Sci U S A. 2007 Nov 13;104(46):18123-8. Epub 2007 Nov 8.

Impacts of plant diversity on biomass production increase through time because of species complementarity.

Author information

  • 1Department of Ecology, Evolution, and Marine Biology, University of California, Santa Barbara, CA 93106, USA. cardinale@lifesci.ucsb.edu

Abstract

Accelerating rates of species extinction have prompted a growing number of researchers to manipulate the richness of various groups of organisms and examine how this aspect of diversity impacts ecological processes that control the functioning of ecosystems. We summarize the results of 44 experiments that have manipulated the richness of plants to examine how plant diversity affects the production of biomass. We show that mixtures of species produce an average of 1.7 times more biomass than species monocultures and are more productive than the average monoculture in 79% of all experiments. However, in only 12% of all experiments do diverse polycultures achieve greater biomass than their single most productive species. Previously, a positive net effect of diversity that is no greater than the most productive species has been interpreted as evidence for selection effects, which occur when diversity maximizes the chance that highly productive species will be included in and ultimately dominate the biomass of polycultures. Contrary to this, we show that although productive species do indeed contribute to diversity effects, these contributions are equaled or exceeded by species complementarity, where biomass is augmented by biological processes that involve multiple species. Importantly, both the net effect of diversity and the probability of polycultures being more productive than their most productive species increases through time, because the magnitude of complementarity increases as experiments are run longer. Our results suggest that experiments to date have, if anything, underestimated the impacts of species extinction on the productivity of ecosystems.

PMID:
17991772
PMCID:
PMC2084307
DOI:
10.1073/pnas.0709069104
[PubMed - indexed for MEDLINE]
Free PMC Article
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