内蒙古典型草原不同地形单元放牧对土壤微生物量磷及磷酸酶活性的影响

土壤微生物量磷和磷酸酶在土壤磷的有效化过程中起着极为重要的作用。过度放牧干扰微生物主导的草原土壤磷的有效化过程，地形也会驱动土壤磷的形态转化和积累。然而，地形与放牧强度的交互作用对土壤微生物参与磷活化过程的影响尚不明确，它们对不同地形单元放牧强度的响应可能存在差异。基于十年定位不同地形单元(坡地和平地)放牧试验，研究不同地形单元放牧对土壤磷酸酶活性和微生物量磷(SMBP)的影响。结果表明，地形而不是放牧显著影响土壤全磷(TP)、有机磷(P_O)、有效磷(Olsen-P)含量。坡地SMBP含量显著低于平地，平地重牧(G7.5-G9.0)显著提高了SMBP含量，而坡地放牧则对其没有显著影响。土壤碱性磷酸酶(ALP)和磷酸二酯酶(PD)活性的变化只受放牧影响，而酸性磷酸酶活性(ACP)受地形驱动。平地土壤PD、ALP活性与土壤理化性质间存在复杂的联系，且与放牧强度呈负相关关系，而坡地则只保留了土壤PD活性与磷、全氮(TN)的联系。平地和坡地的土壤ACP活性与土壤化学性质无关。土壤含水量(WC)驱动了平地和坡地SMBP和磷酸酶活性的差异，其中WC、P_O...

Effect of grazing on soil microbial biomass phosphorus and phosphatase activities on different topographic unit of a typical steppe

Overgrazing interferes the grassland soil process of phosphorus (P) availability which is dominated by microorganisms, and topography also drives the P transformation and accumulation in soil. Soil microbial biomass phosphorus (SMBP) and enzymes involved phosphorus mineralization played important roles in soil P transformation. However, the effect of the interaction between topography and grazing rate on the participation of soil microorganisms in phosphorus activation process is not clear. In this study, the effects of grazing on the activities of soil alkaline phosphatase (ALP), acid phosphatase (ACP), phosphodiesterase (PD), and SMBP were investigated based on a ten-year grazing experiment (0, 1.5, 3.0, 4.5, 6.0, 7.5 and 9.0 sheep/hm²) on two topography treatments (slope and flat). This study hypothesized that 1) due to the soil water content (WC) of slope treatment is lower than the flat treatment, and so do soil nutrient properties, so the effect of slope treatment on SMBP is stronger than flat soil; 2) due to the slope soil lack of phosphorus than flat soil, so the activities of ALP, ACP, PD are higher than flat soil; 3) slope soil is facing higher nutrient limit caused by the difference of parent material, and water limit caused by topography, so, there may be different environmental factor driving the change of SMBP and enzymes. The results showed that topography, not grazing, significantly affected soil TP, P_O and Olsen-P. SMBP in slope treatment was significantly lower than that in flat treatment. SMBP was significantly increased by heavy grazing on flat treatment, but not on slope treatment. ALP and PD activities were only affected by grazing, while the activities of ACP were driven by topography. There was a complex relationship between the activities of PD, ALP and soil physical and chemical properties in the flat group, and there was a negative correlation between the activities of PD, ALP and grazing rate, while only the relationship between PD activities, phosphorus and TN was maintained in the slope group. The ACP activity of flat group and slope group was not related to soil chemical properties. Soil water content drives the difference between flat land and sloping land. Considering topographic factors, soil water content, P_O, TP and TN drive the change of flat soil, while slope soil is affected by soil water content, P_O and TOC. In conclusion, topography drives the response of SMBP phosphorus and phosphatase activity to grazing. This article indicates that, under grazing, the process of soil microorganism activities phosphorus is affected by different factors on flat and slope grazing treatments, and soil water content plays an important role.