Correlation of the abundance of bacteria catalyzing phosphorus and nitrogen turnover in biological soil crusts of temperate forests of Germany

Abstract

Soil P pools are strongly driven by microbial activities, and vice versa, P pools shape bacterial communities and their functional potential. Biological soil crusts (biocrusts) represent a microbial hotspot for nutrient turnover. We compared biocrusts and bulk soil samples from different temperate beech ( Fagus sylvatica L.) forests representing a gradient in soil texture, nutrient concentrations, and pH values at biocrust peak biomass. We measured the total and plant-available P and N concentrations and assessed the bacterial potential to mineralize ( phoD , phnX ), solubilize ( gcd ), and take up P ( pstS and pitA ) and mineralize ( chiA , apr ) and fix N ( nifH ) by quantifying the respective marker genes (qPCR). We found an increase of absolute and relative bacterial abundance involved in P turnover in biocrusts, but the strategy to acquire P differed between the regions as bacteria harboring the starvation-induced pstS gene were most abundant where labile P was lowest. In contrast, the region with lowest total P concentrations has a higher potential to utilize more stable phosphonates. N mineralization was strongly correlated to P turnover at regions with increased labile N and P concentrations. Interestingly, the potential to fix N was highest in the bulk soil where total P concentrations were highest. Even though the correlation of N and P turnover is strongest if their ratio is low, the acquisition strategy strongly depends on soil properties.

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