Buffering potential of plant diversity on the spatiotemporal variability of annual biomass increments at the plot and field scale in semi-natural grasslands

Biomass production in semi-natural grasslands varies depending on anthropogenic disturbances caused by land-use practices and natural disturbances such as droughts during the growing season. Species insurance effects, in particular compensatory effects of plant species diversity, are well researched with regard to the stability of biomass production across several years at the plot scale. However, it is not sufficiently understood if there are similar buffering effects of plant species diversity on the variability of biomass increments on a much shorter time scale within a season and at a larger spatial extent. We therefore aim to investigate how mowing and grazing intensity affect the buffering potential of plant species diversity on the spatiotemporal variability of annual biomass increments and how this differs between a drought year (2020) and a non-drought year (2021) in entire grassland fields of two German regions. We used upscaled time series of biomass production from every two weeks during the growing season to calculate the variability of annual biomass increments, as well as spatially upscaled annual predictions of species diversity and land-use intensity, all based on satellite imagery. In our study, we go beyond the plot scale and also analyse the larger field scale. In this way, we contribute to the understanding of how biomass increments vary spatially and temporally over the course of the season and what role species diversity and its compensatory effects through space play in this context. We hypothesise that grassland fields that are on average more species-rich and spatially variable in their species diversity are better able to buffer disturbances caused by land-use practices or droughts and lead to a more stable increase in biomass. Furthermore, we expect that this buffering potential is more pronounced at the field scale compared to the smaller plot scale, as results can be more robust when including the heterogeneity of whole grassland fields. Findings of this study can provide insights into the extent to which plant diversity ensures stable annual biomass production and how this buffering potential is influenced by the intensity of land-use practices in semi-natural grasslands across scales.