Mechanism Of The Effect Of Biological Soil Crust On The Availability Of Phosphorus In The Hilly Loess Plateau Region,China

Phosphorus is one of the three essential nutritional elements of plant growth; phosphorus deficiency may one of the reasons that affect the loess hilly region of vegetation to recover. In recent years, the implementation of Grain for Green eco-project in cause a large area of biological soil crusts occurred in the Hilly Loess Plateau region, which exerts a significant impact on soil phosphorus availability in this region. In this study, we studied time and space characteristics and mechanism that abandoned lands biological crusts affect soil phosphorus availability in the Hilly Loess Plateau region following a field investigation, methods of time and space with each other replace. The purpose is to reveal the ecological functions of the biological soil crust, provide scientific basis for vegetation restoration in this area. The results are as follows:(1) The availability of phosphorus was increased significantly for the formation of biological soil crusts. The total soil phosphorus content in biological soil crusts is0.62g/kg, and the soil available phosphorus content is5.87mg/kg. In biological soil crusts layer0.95%of the total phosphorus content is soil available phosphorus, while only0.20%in0-2cm layer and0.09%in5-10cm.(2) The effect of biological soil crusts on soil phosphorus content and availability was related to the time of development, biomass, and biological activity. In biological soil crusts the total soil phosphorus content and the soil available phosphorus content are increase with years of development adding between3to15years. At15th year of abandonment, the total soil phosphorus and soil available phosphorus content reached the maximum; those were5.87mg/kg and0.62g/kg. Abandoned lands biological soil crusts had no significant effect on the soil phosphorus between16to30years. The effect of biological soil crusts on soil phosphorus availability is related to biological components and biomass. In biological soil crusts layer, soil available phosphorus content increased with the biomass of biological soil crusts.In different seasons, difference were found in the effect biological soil crusts on the total soil phosphorus content and soil phosphorus availability. Before the rainy season, in biological soil crusts layer soil available phosphorus content was3.31-6.93mg/kg, accounting for0.59-1.08%of the content of the same layer and same time of the total phosphorus0.75g/kg. In the rainy season was2.20-5.15mg/kg,0.39-0.83%of0.56-0.62g/kg. The end of the rainy season was3.04-5.67mg/kg,0.56-0.93%of0.54-0.61g/kg. At a.m.8:00-10:00biological soil crusts has the highest activity, which has significant impact on soil phosphorus availability, the maximum value was0.25-0.31μg/cm2.(3) There was a significantly spatial variability in the effect of biological soil crusts on soil phosphorus availability. The impact of shady biological soil crust on soil total phosphorus and available phosphorus was significantly, while the sunny slope was not significant. While the sites move down on the shady slope, total phosphorus and available phosphorus content in biological soil crusts layer showed an increasing trend, in the lower position of shady slope, the available phosphorus content was significantly increased to14.82mg/kg, accounting for1.98%of the content of the same layer of total phosphorus0.75g/kg.(4) The effect of biological soil crusts on soil phosphorus availability is related to soil phosphatases, organic matter, calcium carbonate, the pH, microbial biomass phosphorus and biomass, which shows:organic matter> calcium carbonate> biomass> pH> total P> soil phosphatases.