两种退耕还林模式对土壤微生物优势类群的影响

以两种退耕还林模式的桦木林地、苦竹林地和农耕地(对照)为对象,对各样地土壤微生物优势类群数量的季节性动态变化、垂直分布特征及其与土壤酶活性的相关性进行了研究。结果表明,土壤微生物的优势类群为微球菌属(Micrococcus)、芽孢杆菌属(Bacillus)、链霉菌属(Streptomyces)、游动放线菌属(Actinoplanes)、酵母菌(未定属)、木霉菌属(Trichoderma)这6类。两种退耕还林模式下土壤优势微生物类群数量存在差异,春、夏、秋三季均为苦竹林所占比例最大,冬季为桦木林最大。两种林地和农耕地土壤微生物优势类群数量季节性变化规律为微球菌和酵母菌在夏、冬季较大,春、秋季较少;芽孢杆菌在秋季最大,夏季最小;游动放线菌与木霉菌数量在四季中变化不大;链霉菌是夏季最高,冬季最少。各优势微生物类群数量的垂直分布特征表现为微球菌、游动放线菌、木霉菌随土壤层的加深其数量逐渐降低,芽孢杆菌、链霉菌数量则随土壤层的加深而逐渐增加,酵母菌随土壤层的加深其数量减少,但趋势不明显。两种林地对各优势微生物类群数量的根际效应为:链霉菌和木霉菌的R/S值大于1,酵母菌的R/S值小于1,微球菌和游动放线菌在桦木林的R/S值大于1而在苦竹林小于1。在优势微生物类群和土壤酶之间,微球菌与转化酶,芽孢杆菌与纤维素酶,木霉和游动放线菌与过氧化氢酶,酵母与脲酶呈显著正相关关系。

Effects of Two Models of Forest Rehabilitation on Dominant Groups of Soil Microbes

Seasonal dynamic variations and vertical distribution characteristics of preponderant groups of soil microbes and their correlations with soil enzymatic activities were studied in Betula luminifera forest, Pleioblastus amarus forest and cropland(control). Results indicated that there were six preponderant species of soil microbes: Micrococcus, Bacillus, Streptomyces, Actinoplanes, yeast(the genus was not identified) and Trichoderma. The amounts of dominant groups of soil microbes had difference between two models of forest rehabilitation: the ratio in P. amarus forest was the largest in spring, summer and autumn, and the ratio of B. luminifera forest was the largest in winter. Seasonal variations of dominant groups of soil microbes in two forests and cropland were that amounts of Micrococcus and yeast were higher in summer and winter than spring and autumn; Bacillus was the highest in autumn and the least in summer; Actinoplanes and Trichoderma were less change than other dominant groups with season; Streptomyces was the highest in summer and the least in winter. Vertical distribution characteristics of dominant groups were that amounts of Micrococcus, Actinoplanes, Trichoderma were reduced gradually with soil depth, but Bacillus and Streptomyces were opposite to them; and change of yeast was not significant with soil depths. Rhizosphere effects showed that R/S values of Streptomyces and Trichoderma were more than 1; R/S value of yeast was less than 1; and R/S value of Micrococcus and Actinoplanes was more than 1 in Betula luminifera forest, but opposite in Pleioblastus amarus forest. There were significant positive correlations between Micrococcus and invertase, Bacillus and cellulase, Actinoplanes-Trichoderma and catalase, and yeast and urease.