不同耕地利用方式下土壤微生物活性及群落结构特性分析: 基于PLFA和MicroRespTM方法

研究不同耕地利用方式对土壤微生物群落结构的影响,对维持土壤稳定和提高土壤质量具有重要意义.以湖南省桃源县长期定位试验为平台,采用磷脂脂肪酸(PLFA)和MicroRespTM方法,研究了稻田、水旱轮作地和旱地这3种不同耕地利用方式下土壤微生物数量、群落结构特征及活性.PLFA结果表明,细菌、真菌及总PLFA量均表现为稻田>水旱轮作地>旱地,细菌PLFA/真菌PLFA比值则表现为水旱轮作>旱地>稻田.革氏阳性菌(G+)PLFA/革氏阴性菌(G-)PLFA为稻田显著高于水旱轮作地和旱地,但水旱轮作与旱地土壤的差异不显著.PLFA主成分分析和特征磷脂脂肪酸的平均摩尔分数表明,稻田中真菌及G-的相对含量显著高于水旱轮作地和旱地,而水旱轮作地中G+的相对含量高于旱地和稻田,3种不同耕地利用方式下土壤微生物群落结构特征具有明显差异.土壤PLFA与土壤养分相关性分析表明,土壤微生物量与土壤有机碳(SOC)、全氮(TN)、土壤微生物量碳(MBC)均达到极显著正相关.与阳离子交换量(CEC)无显著相关性.MicroRespTM结果表明,3种不同耕地利用方式下土壤微生物对碳源平均利用效率为稻田最高,其次是水旱轮作地,旱地最低.其结果也显示大部分碳源提高了微生物呼吸作用,但不同碳源的利用效率不相同.因此,耕地利用方式的不同明显导致了土壤微生物活性和群落结构的差异.

Microbial Activity and Community Structure Analysis Under the Different Land Use Patterns in Farmland Soils: Based on the Methods PLFA and MicroRespTM

Soil microbe plays an essential role in terrestrial ecosystem through its role in cycling mineral compounds and decomposing organic matter. The objective of this paper is to determine the influences of different land use patterns on soil microbial activity and community structure, which were analyzed by phospholipids fatty acid (PLFA) and MicroResp^TM method, based on a long-term fertilization experiment in Taoyuan County, Hunan Province. There were three land use patterns included, i. e. paddy fields (PS), paddy-upland rotation (PU) and upland land (US) soils. The results showed that the amounts of bacteria PLFA, fungi PLFA and the total PLFA were generally following the order PS>PU>US. The ratio of bacteria PLFA/fungi PLFA followed the order PU>US>PS, however, the ratio of Gram-positive bacteria PLFA (G⁺ PLFA) to Gram-negative bacteria PLFA (G^-PLFA) in PU was the highest, and there's no significant difference in PU and US. In addition, principal components analysis (PCA) and the average concentration (mol·mol^-1) of biomarker-PLFAs also revealed that the relative content of fungi and G^- in PS was much higher than those of in PU and US (P<0.05). However, the relative content of G⁺ in PU was higher than those of other two land use patters. Therefore, Microbial community structure was influenced significantly by land use patterns in our study. Soil microbial biomass had significant relationships (P<0.05) with SOC, TN and MBC, but had no significant correlation with CEC. Meanwhile, MicroResp^TM analysis indicated that most of the carbon substrate addition enhanced the microbial respiration rates, although different substrate had different use efficiency. The average of carbon substrate use efficiency could be also ranked in the order: PS>PU>US. We conclude that microbial activity and community structure were influenced significantly by land use patterns in farmlands.