Resource fluctuations and niche separation in plant communities: Can land-use effects on soil moisture explain observed patterns in plant diversity?
Zusammenfassung der Projektergebnisse
In this project, we build the necessary competences and methods to address the question on the relationship between soil moisture uctuations and plant species richness in temperate grasslands. Due to various complications during the project, we are not in the position to offer final results yet, although all relevant data were collected and methods established. Our analysis shows that variability in soil moisture, represented either as sum exceedence values proposed originally or as wavelet decomposition of observed soil moistures, is uncorrelated with plant species richness in the grassland plots of the Biodiversity Exploratories. Although species display clear preferences for a position along the drought-flooding-trade-off gradient, this seems to be insuffcient to provide a mechanism for coexistence in the field. In mesocosms, environmental conditions filtered plant species for those resistent to occasional drought, thereby homogenising the plant types available for the analysis. Again, although soil moisture fluctuations very clearly affected biomass accumulation in the mesocosms, no effect on plant species richness was detected in our preliminary analyses. Soil moisture data in the field often exhibit gaps in the records due to device failure. We used a hydrological model to fill in those gaps based on precipitation data and soil profiles. This approach provided a reasonable prediction of trends of soil moisture over days or weeks, but failed to recover short-term dynamics and spikes in soil moisture. Although the project has terminated, we are currently working on further analyses.
