Land Degradation & Development：农业用地变化对土壤有机碳稳定性的影响

四川农业大学资源学院王昌全教授课题组采用“空间差异代替时间变化”方法，对成都平原四种典型农业用地情景的有机碳封存和养分有效性的影响进行了评估。相关成果发表于Land Degradation & Development（IF=4.27）

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Abstract

The properties of soil organic carbon (SOC) required for carbon sequestration and nutrient availability are contradictory, and the changes in SOC caused by agricultural land use changes remain elusive. Data on the total soil organic carbon (TOC) and labile organic carbon (LOC), including easily oxidizable organic carbon (EOC), dissolved organic carbon (DOC) and microbial biomass carbon (MBC), of the soil profile were analysed for four typical agricultural land use scenarios in the Chengdu Plain, China. The impacts of agricultural land use changes on sequestration and nutrient availability of SOC were assessed in this urban agricultural area using the space‐for‐time substitution method. Conversion of land use from a traditional agricultural rotation to afforestation increased the MBC content and decreased the contents of EOC, DOC and TOC due to the lower input of organic matter, improved aeration of the soil profile and growth of aboveground biomass. Conversion of a traditional rotation to a rice–garlic rotation resulted in a significant increase in topsoil TOC, slight but insignificant decreases in subsoil TOC, and clear increases in LOC because of rice planting, rice straw mulch and reasonable application of chemical fertilizers. In contrast, the conversion of a traditional rotation to a rice‐leafy vegetable rotation decreased MBC due to the excessive use of chemical fertilizers that consequently increased EOC, DOC and TOC. We conclude that afforestation on paddy soil has negative consequences for soil carbon sequestration, and a rice‐leafy vegetable rotation contributes to carbon sequestration but is detrimental to soil fertility. In addition, the MBC ratio in soil could be the optimal indicator for assessing SOC stability and soil fertility, and more attention should be paid to subsoil carbon changes.

土壤碳封存能力与养分有效性所需的有机碳（SOC）性质是相反的，农地利用变化引起的有机碳变化仍不清晰。本研究分析了成都平原四种典型农业用地情景的土壤总有机碳（TOC）和活性有机碳（LOC）数据，包括易氧化有机碳（EOC）、溶解有机碳（DOC）和微生物生物量碳（MBC）。采用“空间差异代替时间变化”方法，对该地区农业用地变化对有机碳封存和养分有效性的影响进行了评估。土地利用由传统的农业轮作转为林地，会增加MBC含量，降低EOC、DOC和TOC的含量，这是由于林地有机质的投入较低、土层通气状况改善以及地上生物量的增加。将传统轮作改为水稻-大蒜轮作后，由于水稻种植、秸秆覆盖和合理施用化肥，使得表层土壤TOC显著增加，底层土壤TOC略有下降，但幅度不大，LOC明显增加。相比之下，将传统的轮作改为水稻-叶菜轮作后，由于过度使用化肥，导致了EOC、DOC和TOC升高和MBC降低。本研究的结论是，稻田土壤改为林地不利于土壤碳封存，水稻-叶菜轮作有助于碳封存，但不利于土壤肥力。此外，土壤中MBC比例可以作为评价土壤有机碳稳定性和土壤肥力的最优指标，并且应重视底层土壤碳的变化。