signature=312ebde6c2f1b10b11dafae3319c9d8e,Rapid response of soil microbial communities from convent...-优快云博客

研究发现，有机肥料和覆盖作物的使用增加了微生物的碳源，而灌溉导致的土壤干湿循环可能对微生物产生应力。尽管不同农业系统的微生物响应相似，但表面土层的微生物对干燥和再湿润的适应性更强，表现出更快的呼吸速率和微生物生物量碳的增加。此外，深层土壤中的微生物在干湿循环中承受更大压力。研究揭示了微生物群落结构和过程如何随农业实践和环境变化而调整。

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摘要：

Soil microbial communities may be strongly influenced by agricultural practices which change the soil environment. One such practice is the use of organic amendments and cover crops which increase carbon availability to microorganisms. Another is irrigation which, in California's hot, rain-free growing season, can cause severe wet/dry cycles. We investigated (i) long-term differences in amounts of organic inputs using soils from organic, low input, and conventional farming systems, and (ii) differences in severity of soil drying following irrigation, using soil from two depths, 0–3 and 3–15cm. All soils were air-dried and re-wetted, and we measured short-term changes in microbial biomass carbon (MBC), dissolved organic carbon (DOC), respiration, and phospholipid ester-linked fatty acid (PLFA) composition before and for 27h after re-wetting. Respiration rates were fit to a two-first-order-component model. Carbon respired from the more slowly utilized C pool of the two-component model, MBC, and DOC increased with increasing amounts of organic inputs, and PLFA composition of the organic and conventional soils clearly differed in their mole percentages of numerous fatty acids when analyzed by principal components analysis and redundancy analysis. Despite these differences, the response of microbial communities in the three farming systems to soil drying and re-wetting was similar. For example, the relative increase in MBC following soil re-wetting did not differ among the farming system soils. In contrast, the relative increase in MBC after re-wetting was greater, and the respiratory response to soil re-wetting was more rapid in the surface (0–3cm) than deeper (3–15cm) layer. Higher ratios of cyclopropyl fatty acids to their precursors suggested greater stress to bacteria in the deep than surface layer, and these ratios declined more rapidly after re-wetting in the deep than surface layer. This study suggested that adaptation to wet/dry cycles by surface microorganisms had occurred during the 3-month growing season, leading to changes in both microbial process rates and community composition.

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