岷江流域不同土地利用类型土壤养分及微生物群落多样性研究

摘要

以四川省岷江流域不同土地利用类型（次生林、人工林、灌草丛和坡耕地）土壤为研究对象，利用Biolog微平板法和磷脂脂肪酸甲酯（ FAMEs）法系统研究微生物群落多样性特征以及在不同土地利用类型的分布规律。结果表明：各土地利用类型土壤均略显酸性，pH值高低依次为坡耕地、灌草丛、人工林和次生林，土壤电导率、容重和孔隙度有所波动；土壤养分含量和有效养分含量高低大致依次为次生林、人工林、灌草丛和坡耕地。不同土地利用类型土壤微生物群落代谢平均颜色变化率（ average well color development，AWCD）随培养时间延长而逐渐增加，土壤微生物群落代谢活性大小依次为次生林、人工林、灌草丛和坡耕地。土壤微生物对不同种类碳源的利用强度存在较大差异，羧酸类和碳水化合物类碳源是不同土地利用类型土壤微生物的主要碳源，其后依次为酚酸类、氨基酸类和聚合物类，而土壤微生物对胺类碳源的利用率最小。土壤微生物群落丰富度指数（ H）、均匀度指数（ E）、优势度指数（ DS ）和碳源利用丰富度指数（ S）总体表现为次生林最高，人工林和灌草丛次之，坡耕地最低，不同土地利用类型间DS差异未达显著水平（ P＞0．05）。主成分分析结果表明，从31个因素中提取的与碳源利用相关的主成分1和2分别能够解释变量方差的63．89％和18．55％，在主成分中贡献最大的是羧酸类和碳水化合物类碳源；土壤微生物多样性指数与土壤有机质含量和全氮含量之间均达显著或极显著正相关，与pH值呈负相关，即土壤有机质含量和全氮含量对土壤微生物多样性影响较大。上述研究结果表明次生林土壤养分含量更高，更适合土壤微生物生存，这对于维持该区域生态系统功能稳定性具有重要意义。%The Minjiang River Valley in Sichuan is a region diversified in type of land use ( shrub⁃grassland, slope farm⁃land, planted forest and secondary forest). Soil microbial community diversity and distribution of different types of land use in the region was studied using the Biolog plate and phospholipid fatty acid methyl ester ( FAMEs) methods, separately. Results show that the soils regardless of whatever type of land use were undertended to be slightly acidic, following an or⁃der of slope farmland>shrub⁃grassland>planted forest>secondary forest in soil pH, fluctuated somewhat in soil electric conductivity, bulk density and total porosity, and followed an order of secondary forest> planted forest>shrub⁃grassland >slope farmland in content of soil nutrients and available nutrients. The soils varied significantly in functional diversity of microbial community relative to land use. Average well color development ( AWCD) is an index that directly reflects soil microbial activity and functional diversity. It increased with the usage going on time. The soils displayed an order of sec⁃ondary forest > planted forest > shrub⁃grassland > slope farmland in soil microbial community activity. Soil microbes′ use of carbon sources varied in intensity relative to type of the source. Carboxylic acids and carbohydrates were the major ones and followed by amino acids, phenolic acids, polymers, and amines. The soils also displayed the order of secondary forest > planted forest > shrub⁃grassland > slope farmland in Simpson index ( H) , Shannon⁃Wiener index ( E) , richness index ( DS ) and McIntosh index ( S) , but the differences between the four types of land use in DS were not big enough to be rated as significant. Principal component analysis ( PCA) shows that principal components No. 1 and No. 2 out of 31 af⁃fecting factors related to carbon source utilization explained 63�89% and 18�55% of the variation, respectively. Among the principal components, carboxylic acids and carbohydrates were the two major contributors. Correlation analysis shows that soil microbial diversity index was in significantly or very significantly positive relationship with the content of soil organic matter and of total nitrogen, but in negative one with pH, that is to say, the content of soil organic matter and the content of total nitrogen are the two major factors affecting soil microbial diversity. All findings mentioned above suggest that the soil under secondary forest is the highest in nutrient content and more favorable for survival of microorganisms, which play a very important role in maintaining stability of the ecosystem in this area.