Download Biodiversity and ecosystem functioning

Biodiversity and ecosystem functioning
Jan Lepš, Department of Botany, Faculty of Science, University of South Bohemia, České Budějovice,
Czech Republic
Many (probably most) ecologists believe that biodiversity begets better ecosystem functioning.
However, in my view, the support for this belief is not always unequivocal. In particular, the BEF
(Biodiversity – Ecosystem Functioning) experiments, where the biodiversity (usually of plants) is
manipulated, and the ecosystem functioning is measured provide many interesting theoretical
insights, and demonstrate many ecological mechanisms, but their correspondence to the real world
ecosystems is questionable. This is mainly because in the real world, the species richness of a
community is a result of ecological forces shaping community species composition: dispersal
limitation, environmental filtering and biotic interactions. On the contrary, in BEF experiments, the
species composition is determined by the experimenter. This roughly corresponds to dispersal
limitation, but in real communities, the species richness is shaped more by environmental filtering
and by competitive exclusion. This is particularly true for the European semi-natural grasslands,
which correspond best to the communities, where the BEF experiments are carried out. In my view,
there is no reason, why communities that are species poor because of harsh environment should
behave in similar way as communities where the species richness is limited by competitive exclusion.
Also, both the models and empirical data show that the sown and realized species richness is related
to ecosystem functioning in different ways.
I will discuss the relationship on species richness with two characteristics, usually presented as
measures of ecosystem functioning: the productivity and the stability. I will show that the support
for diversity begets stability is probably better that for the belief that diversity supports the
productivity. Nevertheless, other factors, mainly the life-history strategies of the constituent
species, are at least as important as the diversity for various stability characteristics.