外来物种刺槐对土壤微生物功能多样性的影响

以延河流域不同植被区内人工刺槐(Robinia pseudoacacia)群落和乡土植物群落的土壤微生物为研究对象,利用Biolog微平板技术对土壤微生物功能多样性进行测定,分析人工引种刺槐在不同环境梯度(3个植被区)下对土壤微生物功能多样性的影响。结果表明:刺槐对不同环境梯度下的土壤微生物的影响明显不同。从草原区到森林区,刺槐林之间土壤微生物群落的平均颜色变化率(AWCD)和土壤微生物功能多样性指数均没有显著变化;但与乡土植物群落比较,草原区、森林草原区和森林区土壤AWCD分别表现为刺槐乡土植物、刺槐乡土植物、刺槐乡土植物;在草原区和森林草原区刺槐林土壤微生物群落的群落丰富度指数(S)、Shannon-Wiener指数(H)、Simpson指数(D)、Mc Intosh指数(U)均大于乡土植物,森林区刺槐林群落丰富度指数(S)、Shannon指数(H)、Simpson指数(D)均小于乡土植物;刺槐林和乡土植物群落下土壤微生物碳源利用存在差异,主要体现在对糖类、氨基酸类的利用上。PCA分析显示主成分1贡献较大的碳源有24种,在主成分分离中起主要贡献作用的是糖类、氨基酸类和羧酸类。土壤碳氮含量能影响土壤微生物功能多样性指数,土壤含水量和温湿度能够影响碳源的利用类型。刺槐对土壤微生物功能多样性的影响存在区域差异,在评价刺槐对土壤生态过程与功能的影响时必须要考虑这种空间差异性。

Effects of the exotic black locust on the functional diversity of soil microorganisms

The functional diversity of soil microbial communities was studied in order to investigate the effects of black locusts and native species on microbial community diversity under different vegetation types. The soil microbial community was compared in areas with different vegetation zones that were inhabited by black locusts and native species. We used the Biolog technique to study soil microbial functional diversity. In this study, we found that introducing the black locust into different vegetation types generated a large variation in soil microbial functional diversity. The trends for the Average Well-Color Development (AWCD) and the functional diversity indices in areas with black locusts were similar in the steppe and forest zones. The values for AWCD and the functional diversity indices, including the Richness index (S), the Shannon-Weiner index (H), the Simpson index (D), and the McIntosh index (U), for the steppe and steppe-forest zone soils containing black locusts were larger than those for the areas with native species. However, the opposite trends were observed in forest zones. Significant differences in the utilization of carbon sources were evident, particularly carbohydrate and amino acid utilization. A Principal Component Analysis (PCA) indicated that the number of carbon sources loaded on PC1 was 24. Carbohydrates, amino acids, and carboxylic acids played major roles in separating the principal components. The soil microbial functional diversities were affected by the soil carbon and nitrogen contents, and carbon source utilization patterns were influenced by temperature and humidity. The effect of the black locust on soil microbes varied depending on the region, and this must be considered when evaluating its effects on soil ecological processes and functions.