Bioavailable phosphorus distribution in alpine meadow soil is affected by topography in the Tian Shan Mountains

Phosphorus(P) bioavailability is an important factor in alpine meadows and plays an important role in the response to climate change and the maintenance of ecosystem functioning.However,little is known about how environmental factors,such as elevation and slope aspect,affect soil P bioavailability.We explored the effects of elevational gradient and slope aspect on different forms of P and P availability in the alpine meadows on the southern slope of the Tian Shan Mountain range.Total P was found to be 851.9-1556.7 mg·kg^(-1) at different elevational gradients and 437.5-1547.0 mg·kg^(-1) at different slope aspects,and highest at 3337 and 3652 m.a.s.l.,but little differences between slope aspects.Olsen P and Labile P linearly increased with the elevational gradient.The valley and the base of the shady slope had higher contents of H_2O-Po.NaHCO_3-Pi,and NaHCO_3-Po,and high-active organic P(NaHCO_3-Po,NaOH-Po,and H_2O-Po) was positively correlated with soil total carbon(TC),total nitrogen(TN),soil organic carbon(SOC),and aboveground biomass(AGB),but was negatively correlated with pH,aluminum(Al),and calcium(Ca) at different elevational gradients.High-active bioavailable P(H_2OPi,H_2O-Po,NaHCO_3-Pi,and NaHCO_3-Po) was positively correlated with soil SOC and AGB and was negatively correlated with pH at different slope aspects.Our results suggest that soil P availability in alpine meadows is significantly controlled by topographical factors and the valleys and base of shady slopes are reservoirs of high-active bioavailable P.