The effect of land-use related diversity on plant-soil feedbacks and plant-community coexistence

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Results from our previous greenhouse experiments using soil communities from the Biodiversity Exploratories indicate that soil-biota effects along a land-use intensity gradient contribute to species coexistence by influencing plant-species dominance in grassland communities. Land-use related soil-biota effects in our experiments differed especially between grasses and herbs, suggesting a biotic legacy effect of land use on plant-community composition and coexistence in grasslands. However, when comparing plant-soil feedbacks (PSFs) under greenhouse and field conditions, we detected in a recent series of experiments consistent differences between PSF effects. In the field, we observed a generally positive effect of plant diversity on biotic feedbacks. This underlines the importance to consider land-use related diversity effects as plant diversity might drive indirect and intransitive competitive effects in natural vegetation. Previous results from the Biodiversity Exploratories clearly show that land-use intensity affects the diversity across trophic levels (plants, herbivores, pathogens). Therefore, we would like to use the framework of the Biodiversity Exploratories to explicitly test (1) the impact of land-use and land-use related biodiversity on species specific PSFs directly in the field. (2) By setting up a combined plant competition and soil diversity experiment at the different land-use intensities and by explicitly excluding above-and belowground herbivores in a fully factorial design, we will provide additional mechanistic resolution regarding the impact of land-use-related diversity of soil microbial communities as well as of above and belowground herbivores on the strength and direction of PSFs and their consequences for plant-species performance and thus plant-community diversity. Within our experimental approach, we will plan (3) to investigate the individual effects of abiotic factors such as fertilization or soil compactions on PSFs under natural field conditions.As land-use intensity affects the diversity of plants, as the diversity of plants resulted in positive feedback effects on plant growth in a previous field experiment, and as plant growth affects abiotic and biotic soil properties, we will investigate in a series of greenhouse experiments (4) the effect and importance of land-use related soil biota on plant abundance along the land-use gradient by experimentally testing biotic soil legacy and PSF effects of 75 MIPs (3 regions à 25 MIPs) in grasslands screening a large set of common plant species. These data will yield important information on the contribution of land-use related soil biota on plant species abundance and community composition, and will be provide substantial information for other soil biota and plant related groups (e.g., for species selection for further studies). With our experiments we hopefully substantially contribute to the study of mechanisms enabling plant-species coexistence.