不同放牧强度对典型草原土壤胞外酶活性的影响

Effects of different grazing intensities on soil extracellular enzyme activities in a typical steppe grassland

与碳(C)、氮(N)和磷(P)分解矿化相关的土壤胞外酶的相对活性可以揭示微生物的生长和代谢过程。为探讨不同放牧强度对典型草原土壤胞外酶活性的影响,本研究对不同放牧强度下0-10和10-20cm土层的胞外酶活性展开调查。本研究的胞外酶包括:β-1,4-葡萄糖苷酶(BG)、β-1,4-N-乙酰葡糖氨糖苷酶(NAG)、亮氨酸氨基肽酶(LAP)、磷酸酶(AP)。结果显示:0-10cm土层,轻度放牧强度显著增加NAG和LAP活性;中度放牧强度显著增加了BG, NAG, LAP和AP活性;重度放牧强度显著增加LAP活性。10-20cm土层,轻度放牧强度显著增加NAG和LAP活性;中度放牧强度显著增加BG, NAG和LAP活性。随放牧强度的增加,两个土层土壤胞外酶活性均呈先增加后降低趋势;随土壤深度增加酶活性均呈降低趋势。冗余分析结果表明,土壤胞外酶活性(EEA)在0-10cm土层主要受微生物碳、铵态氮和土壤水分的影响,而10-20cm层受微生物氮、pH值、土壤水分和硝态氮的影响。在本研究区域尺度上,轻度和中度放牧强度下的土壤胞外酶具有更高的活性。

Grazing affects soil extracellular enzyme activities(EEA)which are considered as a quantitative indicator of biogeochemical cycle.In this study,we conducted an experiment of different grazing intensities including contral(CK),light-grazing(L),media-grazing(M)and heavy grazing(H)with three replicates in a typical steppe in Inner Mongolia for four years(2014-2017).We investigated the six-year responses of soil EEA to different grazing intensities at two depths of 0-10 and 10-20 cm.These extracellular enzymes includedβ-1,4-glucosidase(BG),β-1,4-N-acetylglucosaminidase(NAG),Leucine aminopeptidase(LAP)and phosphatases(AP).The results showed that light grazing significantly increased NAG and LAP at the 0-10 cm depth and NAG and LAP at the 10-20 cm depth.Media grazing significantly increased BG,NAG,LAP and AP in the surface and BG,NAG and LAP in the subsurface.Heavy grazing significantly increased LAP in the surface.Redundancy analysis indicated that the patterns of EEA were mainly driven by soil microbial biomass carbon,moisture and NH+4-N in the surface,while by soil microbial biomass nitrogen,pH and NO-3N in the subsurface.Our results suggested that soil EEA responded differentially to different grazing intensities at two depths in this region,which may have implications for carbon and nutrient cycling under grazing.