PS 16-158 - The effect of biodiversity on plant productivity changes over time: A study based on a simple experimental model

Background/Question/Methods

Several studies have shown that increased biodiversity leads to increased productivity in plant communities. This relationship can be explained by a selection effect caused by the dominance of one or a few species that determine productivity, and by a complementarity effect in the use of resources by the different species. However, these effects are likely to change over time, which cannot be observed in short-term experiments that make up the majority of the literature on this subject. To study the evolution over time of the biodiversity-productivity relationship and its underlying mechanisms, we developed an experimental system based on fast-generating very small plants, duckweed (Lemnaceae). In a growth chamber, we grew four species in monocultures and polycultures of all possible combinations for 60 days. At 20-day intervals, we measured relative biomass and species traits such as leaf area, individual mass and specific leaf area. These measurements allowed us to obtain the effect of diversity on the productivity of the different communities.

Results/Conclusions

Our results show an increase in the net effect of biodiversity on productivity over time, caused by an increase in the complementarity effect. Complementarity between the different species had little effect at the beginning of the experiment and contributed more to the biodiversity-productivity relationship at later stages of community development. At these stages, the complementarity effect was caused by the presence of a particular species. We also show that in the presence of other species, these plants showed strong phenotypic plasticity, but these changes did not contribute to the enhancement of the complementarity effect. The experimental system we developed showed changes in the biodiversity-productivity relationship over time, which reinforces the importance of long-term studies on this topic and underscores the effectiveness of duckweed as an experimental model.