PhosForDiv – Phosphate availability as driver of plant biodiversity in forest ecosystems

Temperate forests on phosporus (P)-limited soils such as acid or calcaric soils are expected to show assemblages of plant species that are capable to cope with a low availability of P. However, the links of P availability and phytodiversity in temperate forest ecosystems remain predominantly unknown. This project thus aims at better understanding the impacts of available soil P stocks on plant species diversity, different concepts of P efficiency, P-related plant traits and functional diversity of Central European forests growing on P-limited soils.

We hypothesize that alpha-diversity measures of herbaceous plant types (e.g. legumes, grasses) and trees (beech, spruce) increase with P scarcity along a gradient of P availability. Moreover, the efficiencies of P uptake, P recycling and P use and P-related traits such as mycorrhization, fine root dynamics and nutrient concentrations and ratios in biomass will be explicitly included into the analyses of functional diversity to detect possible interactions with P limitation and species diversity. The project will include both field and greenhouse experiments and elaborates on two model ecosystems (beech and spruce forest). The field assessments will be performed at the five core level II sites of PP 1685 that are located in different German regions (ten study plots per site). Vegetation analyses will be supplemented with plant, fine root, litter and soil sampling for P and nutrient analyses. Based on these data, P efficiencies and P-related traits will be determined for most of the occurring plant species. The data will be upscaled using further data from level II sites in Germany in cooperation with vTI, Eberswalde. In the greenhouse, we will measure growth rates, P efficiencies and P-related traits of tree saplings and different combinations of herb species under two levels of P supply. The use of root space by single species and species combinations can be particularly relevant for P efficiency of plants. Therefore, in-situ root architecture of cultivated plants will be explored using NMR imaging in cooperation with Forschungszentrum Jülich GmbH. Overall, the project will contribute to a better understanding of P cycling in Central European forest ecosystems and to general insights into the relationship between phytodiversity and P availability in forest ecosystems.