短期增温及减少降雨对杉木人工林土壤DOM的数量及其光谱学特征的影响

Effects of short-term global warming and precipitation reduction on the quantity and spectral characteristics of soil DOM in Cunninghamia lanceolata plantation

  • 摘要: 本文选取我国中亚热带杉木人工林土壤进行短期增温以及减少50%降雨试验,利用光谱技术研究增温及减少降雨对土壤可溶性有机质(DOM)数量和结构的影响。试验设对照(CT)、增温(W,土壤温度增高5 ℃)、减少降雨(P,自然降雨量减少50%)、增温与减少降雨交互作用(WP)4种处理。结果表明:1)增温增加了土壤可溶性有机碳(DOC)数量,使DOM的芳香性指数和腐殖化指数减小,结构变得简单易于分解;0~10 cm土层的土壤DOM含有较多的烷烃,酯类物质较少;10~20 cm土层的DOM则含有较多的碳水化合物。2)减少降雨使土壤水分相对减少,土壤DOC的数量降低。0~10 cm土层土壤DOM的芳香性指数和腐殖化程度降低,DOM含有大量的烷烃;而10~20 cm土层土壤DOM的芳香性指数和腐殖化指数升高,碳水化合物少。减少降雨处理使土壤可溶性有机氮(DON)数量增加。3)增温和减少降雨的交互作用增加了DOC和DON的数量,降低了DOM的芳香化程度和腐殖化程度;使0~10 cm土层的DOM含有较多的碳水化合物,而10~20 cm土层的DOM碳水化合物较少。4)对于0~10 cm土壤,增温对土壤DOM的数量及结构的作用最强;随着土壤深度增加到10~20 cm,减少降雨的作用逐渐明显,其对DOM结构的影响也达到显著水平。温度及降水对DOM的数量及化学结构的变化具有重要意义,该研究结果可以为阐释全球气候变化背景下土壤DOM的动态周转及预测未来森林土壤碳氮的变化趋势提供科学依据。

     

    Abstract: As a small but reactive soil organic matter (SOM) pool, dissolved organic matter (DOM) is considered to be a sensitive indicator of the dynamic of SOM and an important component of terrestrial biogeochemical cycle.The quality and quan tity of DOM are crucial in the dynamics of C, N and other nutrients in forest soils because these attributes are closely related to carbon accumulation in soil and nutrient availability to microorganisms and plants.Global warming has been widely recognized and has induced drastic changes in global precipitation patterns.Because temperature and precipitation are the two most important environmental drivers regulating forest SOM cycle, it is critical that we have a solid understanding of the response of soil DOM to such climatic changes.In this study, we conducted a short-term experiment in a Cunninghamia lanceolata plantation in subtropical China that stimulated soil warming and precipitation decline.The objective of the study was to address the effects of the two factors (temperature and precipitation) on the quantity and composition of DOM.The experimental design was a randomized complete block factorial design, with warming and precipitation as fixed factors.The four treatments (each replicated three time) were set up in the experiment included no warming and natural precipitation (CT), warming and natural precipitation (W), no warming and reduced precipitation (P), warming with reduced precipitation (WP).We found that:1) W treatment increased the quantity of labile soil dissolved organic carbon (DOC), but decreased the aromaticity and humification degree of DOM.The 0-10 cm soil layer contained more alkanes and little esters, while the 10-20 cm soil layer had more carbohydrates.2) P treatment resulted in a smaller soil water content, which limited DOC production.In the 0-10 cm soil layer, soil DOM was apparently less humified and less condensed, with much alkanes present.However, in the 10-20 cm soil layer, aromaticity and humification degree were enhanced, while the quantity of carbohydrates decreased.In addition, precipitation decline also improved the quantity of DON.3) The combination of warming climate and declining precipitation increased the concentrations of DOC and DON, and reduced the aromaticity index and humification degree.The 0-10 cm soil layer had relatively more carbohydrates than the 10-20 cm soil layer.4) In the 0-10 cm soil layer, warming climate was the only factor that significantly influenced the quantity and quality of DOM.With increasing soil depth, precipitation decline became the second significant factor influencing soil DOM structure.Our results provided a deeper insight into the dynamic changes of soil DOM under global warming and declining precipitation, which was helpful in more accurately predicting soil C and N cycle in response to future global climate change.

     

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