Impacts of mowing and N addition on soil organic phosphorus mineralization rates in a semi-natural grassland in Northeast China

Aims Phosphorus (P), like nitrogen (N), commonly impacts the structures and functions of terrestrial ecosystems. Global changes (N deposition) and land-use intensification (mowing) may influence the components of P cycling in grassland ecosystems, especially soil organic P mineralization, which provides P for plants and microbes. It remains unclear how soil annual organic P mineralization rate responds to mowing and N addition and its potential mechanisms in the semi-natural grasslands. Methods We conducted a five-year field experiment that included mowing (mown and unmown) and N additions (0, 2.5, 5, 10, 20, and 40 g N m(-2) yr(-1)) to explore the responses of and main factors controlling soil organic P mineralization to these treatments in a semi-natural grassland-Songnen Meadow Steppe. Results We found that N additions enhanced the rate of soil organic P mineralization in semi-natural grassland. The magnitude of positive effects of N additions was larger in mown plots than unmown plots. Compared with no N addition, the rates of soil annual organic P mineralization increased 39.04, 46.88, 90.57, 58.82, and 67.97% under mown as the N input increased, and 23.89, 24.13, 25.46, 33.42 and 34.81% under unmown. The alkaline phosphatase (ALP) activity was the main driver which controlled soil annual organic P mineralization rates under N additions in unmown plots, and the plant aboveground biomass, soil microbial community composition, and ALP activities were the main drivers under N additions in mown plots. Our results indicate that mowing modulated the effects of N additions on the annual organic P mineralization rate in soil. Conclusions The soil annual organic P mineralization rate had stronger dependence on the shifts in plant-soil-microbe variables with N additions in the mown conditions than in the unmown conditions, which highlighted that P cycling may be more susceptible to future environmental changes induced by N deposition under mowing in semi-natural ecosystems. Our study provided the new insight of that plant and soil interactions have an important role in maintaining the supply of P, and they may drive soil organic P mineralization in P-deficient ecosystems as N deposition increases.