放牧对冷蒿根际微生物区系及土壤酶活性的影响

Effects of grazing intensity on soil microbial flora and soil enzyme activities in the Artemisia frigida rhizosphere

为了揭示放牧对退化草原冷蒿Artemisia frigida群落阻击草场进一步退化的机制,以小区控制放牧试验(不放牧、轻度放牧、重度放牧)冷蒿根际与非根际土壤为对象,研究了不同程度放牧干扰对冷蒿根际土壤微生物数量、类群和酶活性的影响及其相互关系。结果表明:各放牧区土壤微生物数量均表现为细菌>放线菌>真菌;各处理之间冷蒿根际土壤微生物细菌、放线菌、真菌数量均显著高于非冷蒿根际土壤(P<0.05)。冷蒿根际土壤氨化细菌和好氧纤维素分解菌数量高于非冷蒿根际土壤;轻度放牧区冷蒿根际土壤氨化细菌和好氧纤维素分解菌数量显著增加(P<0.05)。冷蒿根际土壤轻度放牧后碱性磷酸酶、脱氢酶、淀粉酶、转化酶、脲酶、硝酸还原酶活性明显高于对照和重度放牧;各放牧区冷蒿根际土壤7种酶活性显著高于非冷蒿根际土壤(P<0.05)。相关分析表明,氨化细菌与碱性磷酸酶、脱氢酶、淀粉酶、转化酶、硝酸还原酶活性存在极显著正相关关系(P<0.01),好氧纤维素分解菌与酶活性存在正相关(P<0.05)。重度放牧后土壤中微生物数量减少,酶活性降低,轻度放牧使冷蒿根际土壤微生物数量和酶活性显著增加,改善土壤微生态环境。合理放牧有助于冷蒿阻击草原进一步退化。

To reveal how Artemisia frigida growing in degraded grasslands resisted further degradation, the effects of grazing disturbance at varying degrees（no grazing, the control; light grazing; and heavy grazing） to microorganism quantity, physiological groups, and enzyme activities of soil microbes in the A. frigida rhizosphere, along with the interrelationships among them, were studied. Results showed that the number of microorganisms in different grazing areas was： bacteria actinomyces fungus. The counts of bacteria, actinomyces,and fungi in the A. frigida rhizosphere were significantly higher than in the non-rhizosphere（P〈0.05）. The count of ammonifying bacteria and aerobic cellulose decomposers in the rhizosphere were also significantly higher（P〈0.05） than that in non-rhizosphere; under light grazing, ammonifying bacteria and aerobic cellulose decomposers in the rhizosphere were significantly higher（P〈0.05）. Compared to the control and the heavy grazing treatment, activities of soil alkaline phosphatase, dehydrogenase amylase, invertase, urease, and nitrate reductase in the rhizosphere with the light grazing treatment were higher（P〈0.05）. In each grazing area, seven kinds of soil enzyme activities in the rhizosphere of A. frigida were significantly higher than those in the non-rhizosphere（P〈0.05）. The correlation analysis indicated a highly significant positive correlation between ammonifying bacteria and activities of soil alkaline phosphatase, dehydrogenase, amylase, invertase, and nitrate reductase（P〈0.01）; aerobic cellulose decomposers also had a positive correlation with soil enzyme activities（P〈0.05）. After heavy grazing, the number of microorganisms in the soil decreased, and soil enzyme activities decreased both in the A. frigida rhizosphere and non-rhizosphere. Thus, the number of soil microorganisms and soil enzyme activities in the A. frigida rhizosphere increased with light grazing and improved the soil ecological environment meaning reasonable grazing could help the A. frigida population in degraded grasslands to further resist degradation.