Autor:innen:
Diana Boy | Leibniz Universität Hannover, Institute of Microbiology | Germany
Elisa Diaz Garcia | Leibniz Universität Hannover, Institut für Bodenkunde
Simone Kilian Salas | iES Landau, RPTU Kaiserslautern-Landau
Alberto Andrino | Leibniz Universität Hannover, Institut für Bodenkunde
Hermann F. Jungkunst | iES Landau, RPTU Kaiserslautern-Landau
Georg Guggenberger | Leibniz Universität Hannover, Institut für Bodenkunde
Jens Boy | Leibniz Universität Hannover, Institut für Bodenkunde
Marcus A. Horn | Leibniz Universität Hannover, Institute of Microbiology
Biodiversity and its functional traits are the safety net for mitigating the effects of land-use or climate change. If the functioning of an ecosystem cannot be secured any longer, a tipping point (TP) can be crossed. For tropical soils, a well-known phenomenon is the loss of available forms of phosphorus (P) after disturbances, as P is sequestered in mineral and organo-mineral complexes. In old-growth, functionally diverse forests the acquisition and relocation of P into the nutrient cycle is enabled by specialised microorganisms. However, the P cycle is prone to be affected by disturbances cascading also the carbon and nitrogen cycles. Therefore, microbial mobilization and acquisition strategies are useful proxies to determine TP related to the P-cycle. To test the effects of drought and land-use change on the P-cycle, two different forms of P were offered to the microbial soil communities in a natural setting: apatite, resembling the P-containing bedrock, and inorganic P bound to goethite, one of the most abundant minerals in the tropics. Both minerals were buried in the soil for 3 years along gradients of above-ground biodiversity (from pristine and degraded forests to monoculture and pasture vegetation) with and without artificial rain exclusion. Using molecular tools, we analysed the diversity of bacterial and fungal communities on the minerals and compared them with the communities from spatially close soils. The presence and type of mineral determined significantly the composition of the microbial communities, pointing towards specialised microorganisms responsible for the mobilization of P from hardly accessible sources. We identified several key families preferring the niches in the minerals compared to the soil. While the overall diversity of the soil microbiota is significantly reduced under the pasture, the diversity of the Apatite and P-goethite associated organisms is similar along the entire above-ground biodiversity gradient. The rain exclusion experiment yielded a higher number of species in the minerals under drought conditions compared to the control. These results mirror the communities’ ability to overcome the detrimental effects of P-limited conditions after anthropogenic and natural disturbance by inducing different and increased P acquisition strategies. While we cannot conclude about the crossing of TP in the P-cycle, the results indicate a surprisingly flexible and vivid functional redundancy within the microbial P cycle.