保护性耕作对华中地区水稻（Oryza sativa L.）-小麦（Triticum aestivum L.）种植系统下团聚体内表土微生物代谢特征和有机碳的影响
Effects of Conservation Tillage on Topsoil Microbial Metabolic Characteristics and Organic Carbon within Aggregates under a Rice (Oryza sativa L.)-Wheat (Triticum aestivum L.) Cropping System in Central China.
作者信息
Guo Li-Jin, Lin Shan, Liu Tian-Qi, Cao Cou-Gui, Li Cheng-Fang
机构信息
MOA Key Laboratory of Crop Ecophysiology and Farming System in the Middle Reaches of the Yangtze River/College of Plant Science & Technology, Huazhong Agricultural University, Wuhan 430070, P.R. China.
College of Resources and Environment, Huazhong Agricultural University, Wuhan 430070, P.R. China.
出版信息
PLoS One. 2016 Jan 5;11(1):e0146145. doi: 10.1371/journal.pone.0146145. eCollection 2016.
Investigating microbial metabolic characteristics and soil organic carbon (SOC) within aggregates and their relationships under conservation tillage may be useful in revealing the mechanism of SOC sequestration in conservation tillage systems. However, limited studies have been conducted to investigate the relationship between SOC and microbial metabolic characteristics within aggregate fractions under conservation tillage. We hypothesized that close relationships can exist between SOC and microbial metabolic characteristics within aggregates under conservation tillage. In this study, a field experiment was conducted from June 2011 to June 2013 following a split-plot design of a randomized complete block with tillage practices [conventional intensive tillage (CT) and no tillage (NT)] as main plots and straw returning methods [preceding crop residue returning (S, 2100-2500 kg C ha-1) and removal (NS, 0 kg C ha(-1))] as subplots with three replications. The objective of this study was to reveal the effects of tillage practices and residue-returning methods on topsoil microbial metabolic characteristics and organic carbon (SOC) fractions within aggregates and their relationships under a rice-wheat cropping system in central China. Microbial metabolic characteristics investigated using the Biolog system was examined within two aggregate fractions (>0.25 and <0.25 mm). NT treatments significantly increased SOC concentration of bulk soil, >0.25 aggregate, and <0.25 mm aggregate in the 0-5 cm soil layer by 5.8%, 6.8% and 7.9% relative to CT treatments, respectively. S treatments had higher SOC concentration of bulk soil (12.9%), >0.25 mm aggregate (11.3%), and <0.25 mm aggregate (14.1%) than NS treatments. Compared with CT treatments, NT treatments increased MBC by 11.2%, 11.5%, and 20%, and dissolved organic carbon (DOC) concentration by 15.5%, 29.5%, and 14.1% of bulk soil, >0.25 mm aggregate, and <0.25 mm aggregate in the 0-5 cm soil layer, respectively. Compared with NS treatments, S treatments significantly increased MBC by 29.8%, 30.2%, and 24.1%, and DOC concentration by 23.2%, 25.0%, and 37.5% of bulk soil, >0.25 mm aggregate, and <0.25 mm aggregate in the 0-5 cm soil layer, respectively. Conservation tillage (NT and S) increased microbial metabolic activities and Shannon index in >0.25 and <0.25 mm aggregates in the 0-5 cm soil layer. Redundancy analysis showed that the SOC and its fractions (DOC and MBC) were closely correlated with microbial metabolic activities. Structural equation modelling showed that the increase in microbial metabolic activities directly improved SOC by promoting DOC in >0.25 mm aggregate in the upper (0-5 cm) soil layer under conservation tillage systems, as well as directly and indirectly by promoting DOC and MBC in <0.25 mm aggregate. Our results suggested that conservation tillage increased SOC in aggregates in the topsoil by improving microbial metabolic activities.
研究保护性耕作条件下团聚体内微生物代谢特征、土壤有机碳（SOC）及其相互关系，可能有助于揭示保护性耕作系统中SOC固存的机制。然而，关于保护性耕作条件下团聚体组分中SOC与微生物代谢特征之间关系的研究较少。我们假设在保护性耕作条件下，团聚体内SOC与微生物代谢特征之间可能存在密切关系。本研究于2011年6月至2013年6月进行了田间试验，采用随机完全区组裂区设计，以耕作方式[传统深耕（CT）和免耕（NT）]为主区，秸秆还田方式[前茬作物残茬还田（S，2100 - 2500 kg C ha-1）和去除（NS，0 kg C ha(-1)）]为副区，重复3次。本研究的目的是揭示耕作方式和秸秆还田方式对华中地区稻麦轮作系统表土团聚体内微生物代谢特征、有机碳（SOC）组分及其相互关系的影响。使用Biolog系统研究了两个团聚体组分（>0.25和<0.25 mm）内的微生物代谢特征。与CT处理相比，NT处理使0 - 5 cm土层中土壤总碳、>0.25 mm团聚体和<0.25 mm团聚体的SOC浓度分别显著增加了5.8%、6.8%和7.9%。与NS处理相比，S处理使土壤总碳、>0.25 mm团聚体和<0.25 mm团聚体的SOC浓度分别高出12.9%、11.3%和14.1%。与CT处理相比，NT处理使0 - 5 cm土层中土壤总碳、>0.25 mm团聚体和<0.25 mm团聚体的微生物量碳（MBC）分别增加了11.2%、11.5%和20%，溶解有机碳（DOC）浓度分别增加了15.5%、29.5%和14.1%。与NS处理相比，S处理使0 - 5 cm土层中土壤总碳、>0.25 mm团聚体和<0.25 mm团聚体的MBC分别显著增加了29.8%、30.2%和24.1%，DOC浓度分别增加了23.2%、25.0%和37.5%。保护性耕作（NT和S）增加了0 - 5 cm土层中>0.25和<0.25 mm团聚体的微生物代谢活性和香农指数。冗余分析表明，SOC及其组分（DOC和MBC）与微生物代谢活性密切相关。结构方程模型表明，在保护性耕作系统下，微生物代谢活性的增加通过促进0 - 5 cm上层土壤中>0.25 mm团聚体的DOC直接提高了SOC，同时通过促进<0.25 mm团聚体中的DOC和MBC直接和间接提高了SOC。我们的结果表明，保护性耕作通过改善微生物代谢活性增加了表土团聚体中的SOC。
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