桂北不同林龄桉树人工林土壤微生物数量和酶活性特征研究

为探讨桉树不同林龄土壤微生物活性的响应特征,该研究采用时空互代法,选择广西北部低山丘陵地区1～5年生桉树人工林为研究对象,分析了土壤微生物、酶活性在不同土层和季节的变化规律。结果表明:(1)土壤微生物和酶活性在土层中有明显的垂直分布特征,均随土层加深而趋于降低,且各土层间差异显著。(2)细菌、放线菌数量随季节的大小顺序为秋季>夏季>春季>冬季,真菌的变化规律为春季>夏季>秋季>冬季,而酶活性随季节变化表现为夏季、秋季活性较高,春季、冬季活性较低。(3)细菌、真菌、脲酶、过氧化氢酶随林龄增大表现出先减小后增大的趋势,放线菌则呈现先减小后增大再减小的趋势,而蔗糖酶、酸性磷酸酶随林龄的增大趋于增大。(4)林地土壤中三大类群微生物与四种土壤酶之间存在极显著正相关关系,说明土壤微生物与土壤酶活性相互影响,两者之间关系密切,共同影响土壤的质量。综上可知,不同土层土壤微生物和酶活性的季节响应特征差异较大,总体在冬季最低,主要与气温、水分条件、凋落物养分的归还等有关。不同季节、土层、林龄之间的交互作用对土壤微生物和酶活性有显著影响。

Soil microbe quantity and enzyme activity characteristics of Eucalyptus plantations of different forest ages in North Guangxi

To study the characteristics of soil microbial activity of different forest age of Eucalyptus, using the space-time intergenerational method, we studied the variations characteristics of soil microbes and enzyme activities from four soil depths(0-10, 10-20, 20-30 and 30-40 cm)of different forest ages of Eucalyptus plantations(1, 2, 3, 4, 5 a)at the hilly areas in North Guangxi. The results were as follows:(1)In the soil layers, soil microbial and enzyme activities had obvious vertical distribution characteristics. Both microbial contents and enzyme activities decreased with the deepening of the soil layer, with significant differences among the soil layers.(2)The order of bacteria and actinomycetes contents were autumn > summer > spring > winter, the variation tendency of fungi was spring > summer > autumn > winter, and the enzyme activity changed with season differently, which was higher in summer and autumn, and lower in spring and winter.(3)The soil bacteria, fungi, urease and catalase in the Eucalyptus plantations showed a trend of decreasing first and then increasing with the increase of forest ages, and actinomycetes decreased, increased and then decreased. The activities of invertase and acid phosphatase all increased with the increase of forest ages.(4)There was the significant correlation between the soil microbes and the soil enzymes, indicating that the interaction between soil microbes and soil enzymes had a close relationship, both of which affected the quality of the soil. The seasonal changes of soil microbes and enzyme activities were different in soil layers, which was the lowest in the winter and was mainly related to temperature, water condition and nutrient return of litter and so on. The interactions between different seasons, soil layers and forest ages had significant effects on soil microbes and enzyme activities.