蔬菜-牧草轮作5年草地土壤微生物量变化及其群落结构分异

为明晰蔬菜-牧草轮作系统中种植牧草阶段土壤微生物群落年际和季节间的动态特征,本研究以温带气候区有机农牧场低投入蔬菜生产后种植牧草1~5年和永久性草地土壤为研究对象,运用高通量磷脂脂肪酸(PLFA)分析技术,测定土壤微生物脂肪酸种类和含量,通过非度量多维测度(NMS)排序和多响应置换过程(MRPP)分析,探究牧草不同生长年限和季节条件下土壤微生物生物量及其群落结构与功能变化规律。结果表明:1)随着牧草生长年限的延长,土壤中活体微生物的脂肪酸多样性提高,革兰氏阳性菌与革兰氏阴性菌脂肪酸的比例逐渐降低,真菌与细菌脂肪酸比例升高,微生物生物量增加。2)随着季节更替,特定脂肪酸比例、腐生真菌、厌氧菌生物量发生变化,土壤微生物群落结构亦存在差异。3)牧草生长4年后土壤微生物群落结构发生显著改变且趋近于永久性草地,土壤碳矿化和颗粒有机质含量变化驱动了土壤微生物群落结构分异。

Changes in soil microbial biomass and structural differentiation over 5 years in a vegetable-pasture rotation field

The objective of this study was to analyze the interannual and seasonal changes in soil microbial biomass and community composition in a vegetable-pasture rotation field in a temperate agro-ecosystem. The pasture 1 to 5 years old after low-cost vegetable production were identified for sampling on an organic farm, compared with permanent pasture. The signature fatty acids in microorganisms were determined using a high-throughput phospholipid fatty acid identification method. Nonmetric multidimensional scaling ordination was used to analyze the structure of microbial communities. A multi-response permutation procedure (nonparametric multivariate analysis) was used to examine pairwise comparisons and group significant differences in the proportional abundance of fatty acid methyl esters among rotation year and season. The results showed that: 1) Soil total microbial biomass and the diversity of phospholipid fatty acids increased during the pasture rotation years, with a decrease in the Gram positive to Gram negative ratio, and an increase in the fungi to bacteria ratio. 2) Season significantly affected the ratio of special fatty acid methyl esters and the biomass of saprophytic fungi and anaerobes. The soil microbial community composition also varied among seasons. 3) The microbial community composition changed after 4 years of pasture growth and became more similar to that of permanent pasture. Carbon mineralization and particulate organic matter drove the structural differentiation of microbial communities.