Soil phosphorus and influencing factors in the grasslands at different elevations on westslope of Helan Mountain, Inner Mongolia

In order to understand the soil phosphorus (P) distribution in different types of grasslands at different elevations and analyze the effects of meteorological factors, soil properties and vegetation on the soil phosphorus, a study was conducted on the westslope of Helan Mountain in Alxa, Inner Mongolia. The results indicated that total soil phosphorus (TP) in both 0-10 and 10-20 cm soil layers declined with decreasing altitude and significantly positively correlated (P＜0.05) with the contents of soil organic carbon and soil particle less than 0.05 mm and vegetation coverage. There was no consistent regularity for vertical distribution of TP content along the soil profiles and distribution of soil available phosphorus (AP) along altitude and grassland types. The ratios of AP/TP in both 0-10 and 10-20 cm soil layers significantly positively correlated (P＜0.05) with soil pH and annual average air temperature which suggesting that soil pH and temperature could significantly affect the activation of soil phosphorus. In most of the plots, AP content in 0-10 cm soil layers were significantly higher than that in 10-20 cm soil layers maybe as the result of surface accumulation effects of vegetation to soil phosphorus.