Understanding variation of silicon and calcium in managed grasslands - (BEsic)

• Applicants: Dr. Joana Bergmann; Professor Dr. Jörg Schaller
• Subject Area: Ecology of Land Use ; Soil Sciences ; Ecology and Biodiversity of Plants and Ecosystems
• Term: since 2023
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 512287086

Grassland ecosystems have been the focus of biodiversity research during the last decades while the Biodiversity Exploratories significantly contributed to the field. Plant functional types (PFTs) - e.g. legumes, forbs and grasses - and their representation in the community thereby strongly mediate the nutrient turnover and biomass production in grasslands. A lot of research has focused on land-use related mechanisms driving species turnover processes and biodiversity in these ecosystems. Pasturing and herbivory are two land-use mediated factors driving community shifts that have been well studied in managed grasslands. In this context, it has been suggested that both silicon (Si) and calcium (Ca) may play an important role in grassland functioning. Both elements function as defensive compounds against herbivores while directly influencing the fodder quality for grazing animals. Poales are high Si and low accumulators, while Fabales are low Si and high Ca accumulators. Plant Si and Ca accumulation is related to resource uptake strategy and decomposability along the fast-slow economic spectrum. Due to different plant-species requirements on Si and Ca uptake, their availability in the soil has potential consequences for community composition. Soil Si availability during plant growth can affect grass biomass production and grass nitrogen (N) and phosphorus (P) content. Interestingly, for legumes Ca is known to positively affect nutrition in terms of N and P accumulation and in turn biomass production. It has been shown in the framework of the Biodiversity Exploratories, that land-use intensity and type have consequences for plant community and PFT composition. Recently, a new conceptual model was suggested involving Si and Ca availability as important drivers for the performance of grassland ecosystems. Consequently, apart from dependence on the parent material, soil diagenesis stage and management soil type the proportion of different PFTs is likely to be related to the ecosystem processes affecting Si and Ca availability. Hence, we expect direct and indirect effects between land-use, soil and plant Si and Ca to have the potential to mediate ecosystem processes and services in managed grasslands. The aim of this project is to mechanistically disentangle these effects by investigating variation in Si and Ca in soils, plant communities and single species under different land-use scenarios in the bBiodiversity Exploratories. Therefore, we aim to study the effect of land-use on plant community Si and Ca (objective 1), the filtering effect of soil Si and Ca via shifts in species composition (objective 2) and the environmental effect of soil Si and Ca availability on plastic variation in different species and PFTs (objective 3). We ultimately aim to understand the causal relationships that lead to variation in aboveground biomass Si and Ca in managed grasslands (objective 4).

• DFG Programme: Infrastructure Priority Programmes
• Subproject of: SPP 1374: Biodiversity Exploratories