PARENT SESSION
Oral Session #89: Biodiversity and Ecosystem Function III.
Presiding: R. Washington-Allen
Thursday, August 8. 1:00 PM to 3:45 PM. Coconino Meeting Room, TCC.

Succession leads to rapid convergence of diversity and productivity in experimental communities.

SCHMID, BERNHARD^*,1, PFISTERER, ANDREA¹, JOSHI, JASMIN¹, FISCHER, MARKUS¹, ¹ University of Zurich, Zurich, Switzerland

ABSTRACT- We tested whether higher species richness and functional diversity increase the temporal stability of experimental plant communities and their most important ecosystem function, biomass production. From 1995 to 1999 we studied ecosystem functions under extinction scenarios in 64 synthesized grassland communities with diversities ranging from 1-32 species and 1-3 functional groups. During this period we prevented invasion by weeding. Thereafter, we opened species pools and monitored invasion, extinction and biomass production for another two years. As long as communities were weeded only few species went extinct, a pronounced positive diversity-production relationship was maintained, and diverse systems were more temporally stable in their biomass production. In contrast, opening of the species pool led to rapid convergence in realised diversity and production of communities of different initial diversity, due to both higher extinction rates from more diverse and higher invasion rates into less diverse communities. Moreover, biomass production was increased in more diverse systems also in the longer term, contradicting rapid resource depletion in more diverse communities. The increased temporal stability of biomass production for more diverse systems implies that the production of more diverse systems is more predictable. The minor role of competitive exclusion in weeded communities demonstrates that biodiversity-manipulation experiments with closed species pools, i.e. experiments simulating actual species loss, can indeed be maintained over several years to study longer term ecosystem processes.

KEY WORDS: Biodiversity, Ecosystem functioning, Extinction, Invasion