沙化对玛曲高寒草甸土壤微生物数量及土壤酶活性的影响

对不同沙化程度高寒草甸土壤物理性质和土壤酶活性及微生物结构进行调查分析,结果表明:(1)随沙化程度的加剧,玛曲高寒草甸土壤粘粒成分、含水量、蔗糖酶活性、脲酶活性、中性磷酸酶活性以及过氧化氢酶活性均呈现出下降趋势,而土壤细砂粒成分和pH值逐渐增大,土壤粗砂粒、细菌数量、真菌数量、放线菌数量以及微生物总数量均出现了先增大后减小的趋势。(2)在发生沙化的高寒草甸土壤中,细菌占土壤微生物的主要组分,然后依次是放线菌和真菌;细菌百分比在中度沙化的样地土壤中达到最大值,放线菌和真菌百分比在轻度沙化的样地土壤中达到最大值。(3)在玛曲高寒草甸沙化过程中,驱使土壤微生物数量变化的主导因子是土壤孔隙度和含水量;驱使土壤酶活性变化的主导因子,在沙化初期是土壤含水量、颗粒组成、动植物和pH,在沙化发生后是土壤微生物、颗粒组成、含水量及动植物。

Effect of desertification on soil microbial biomass and enzyme activities in Maqu alpine meadow

Maqu County is located in southwest Gansu Province, which is an important part of the Qinghai Tibet Plateau, and is one of main water conservation districts of the Yellow River. Maqu alpine meadow is an important natural forage resource of China, and is key to the livelihood of local herdsmen. In recent years, desertification has become a serious threat to the ecosystem of Maqu alpine meadow due to the combined effects of anthropogenic and natural factors. The aim of this study was to investigate the effects of desertification on soil microbial biomass and enzyme activities in Maqu alpine meadow. According to the standard of desertification, we selected three types of desertification grade plots and one type of non-desertification plot in August 2013. Soil samples were collected from 0-20 cm depths of typical areas of these plots and were brought to the laboratory. The soil physical properties, soil microbial populations, and enzyme activities were determined, and the relationships between them in different desertification degrees were analyzed. The results were as follows:1) With the aggravation of the desertification degree of Maqu alpine meadow, the clay particle content, water content, invertase activity, urease activity, neutral phosphatase activity, and catalase activity in soil gradually decreased. At the same time, soil fine sand content and pH gradually increased, and coarse sand content, biomass of bacteria, fungi, actinomycetes, and total biomass of microorganisms increased first and then decreased. 2) In the desertification soil, the main microbial component was bacteria, followed by actinomycetes and fungi. The percentage of bacteria reached a maximum in the moderate desertification soil, and actinomycetes and fungi showed the maximum value in slight desertification soil. 3) During the desertification proceed of Maqu alpine meadow, the dominant factors driving the change in soil microorganism biomass were soil porosity and water content. The prime factors causing changes in soil enzyme activities were soil water content, porosity, pH, and flora and fauna in the early desertification soil, and soil microorganism, porosity, water content, and flora and fauna in the late desertification soil. Thus, desertification directly changed the soil particle composition and vegetation of Maqu alpine meadow, and indirectly changed the soil microbial populations. Therefore, the first task for restoring the Maqu alpine meadow ecosystem is to reverse desertification using biological and mechanical measures.