From selection to complementarity: shifts in the causes of biodiversity-productivity relationships in a long-term biodiversity experiment

Abstract

In a 10-year (1996-2005) biodiversity experiment, the mechanisms underlying the increasingly positive effect of biodiversity on plant biomass production shifted from sampling to complementarity over time. The effect of diversity on plant biomass was associated primarily with the accumulation of higher total plant nitrogen pools (N g m-2) and secondarily with more efficient N use at higher diversity. The accumulation of N in living plant biomass was significantly increased by the presence of legumes, C4 grasses, and their combined presence. Thus, these results provide clear evidence for the increasing effects of complementarity through time and suggest a mechanism whereby diversity increases complementarity through the increased input and retention of N, a commonly limiting nutrient.

Figure 1

Temporal trends in the slopes of the net, selection and complementarity effects versus species number in 1996–2005. Error bars indicate 1 s.e. Only four of the slopes are not significantly different from zero: complementarity in 1996 and 1997 and selection in 1998 and 2004.