关键词: 黄土峁状丘陵区, 不同类型林分, 土壤微生物, Biolog, 主成分分析

Abstract: [Objective] In order to evaluate the typical vegetation types used for reforesting formerly cultivated land from the microbial point of view, the main planting tree species of Caragana korshinskii, Robinia pseudoacacia, Pinus tabulaeformis, Platycladus orientalis and Populus alba var. pyramidalis on the sloping land in Mizhi County of Shaanxi province were selected to study the soil microbial metabolic diversity. The purpose of this study was to provide a scientific basis for vegetation restoration and cultivating forests with reasonable structure and favorable ecological function in this area.[Method] The five types of forests were targeted with the nearby abandoned farmland served as the control. Soil samples were collected from all the sloping land. The soil microbial metabolic activity (AWCD), the soil microbial metabolic diversity index (Shannon index, Simpson index and McIntosh index) and the utilization characteristics of soil microbial community to different carbon sources (carbohydrates, amino acids, carboxylic acids, polymer, polyphenols and amines) were studied by using the Biolog-ECO micro-plate technique. The principal component analysis (PCA) method was used to analyze the carbon metabolic characteristics of soil microbial community in the different types of stands.[Result] The soil microbial metabolic activity was significantly increased in the five forests. The AWCD values of soil in the different types of stands followed the order of C. korshinskii > R. pseudoacacia > P. tabulaeformis > P. orientalis> P. alba var. pyramidalis > the abandoned farmland. The soil microbial metabolic activity of C. korshinskii forest was the highest. The Shannon index, Simpson index and McIntosh index of soil microbial community in five types of stands were significantly higher than that in control. Both the Shannon index and Simpson index of C. korshinskii forest were higher than the other four forests (P<0.05). The McIntosh index of soil microbial community of R. pseudoacacia forest was the highest (P<0.05). The utilization rates of carbohydrates, amino acids, carboxylic acids, polymer, polyphenols and amines by soil microbes in the five forests were higher than that in the abandoned farmland, and different carbon sources utilization ability varied among the different forests. The main carbon sources utilized by soil microbes in the five forests were carbohydrates, followed by amino acids, carboxylic acids and polymer, while the utilization rates of polyphenols and amines by soil microbes were very low. PCA analysis indicates that the numbers of carbon sources in relation to PC1 and PC2 are 20 and 17 respectively. Carbohydrates, amino acids and carboxylic acids played a major role in the separation of principal component. The soil microbial community of P. tabulaeformis forest, P. alba var. pyramidalis forest and the abandoned farmland had similar characteristics of carbon sources utilization, while soil microbial community in the other three forests had their unique carbon utilization modes. Moreover, the C. korshinskii forest distributed in the positive direction of PC axis, which demonstrated that the carbon sources utilization ability of soil microbial community in C. korshinskii forest was the best.[Conclusion] The plantations were more beneficial to improve soil microbial metabolic activity than the abandoned farmland in the hilly-gully regions of Loess Plateau. C. korshinskii was better in improving soil metabolic functional diversity than the other studied artificial forests. This study provides to a certain degree a scientific basis for forest species selection and forest cultivation in the project of converting farmland into forest in the hilly-gully regions of Loess Plateau from the aspect of the soil microbial metabolic activity.

Key words: the hilly-gully regions of loess plateau, different types of stand, soil microbes, Biolog, principal component analysis