福寿螺入侵对稻田土壤温室气体排放的影响及其过程机制

Being two important aspects of global change, greenhouse gas emissions and biological invasions have been widely concerned in a broad sense currently. Paddy soil is an important source of methane and nitrous oxide and soil animals have an important regulatory role on greenhouse gas emissions. At present, most of the related studies mainly focus on the changes of soil physical-chemical properties and greenhouse gas emissions caused by indigenous soil fauna, while little attention has been paid to the changes of soil habitat, soil greenhouse gas emissions and related processes caused by the invasion of alien fauna. Golden apple snail (GAS, Pomacea canaliculata) is one of the 100 harmful invasive alien species in the world. In 2003, GAS was included in the "blacklist" of 16 invasive alien species in China. GAS feeds rice seedlings in paddy fields and posed a huge damage on rice production. In addition, it can change drastically the ecological environment and soil state. At present, there are very few studies on the change of related process of soil greenhouse gas emissions affected by GAS with characteristic of high adaptability, rapid growth and large size, which include behavior parameters, plant damage, metabolism and soil disturbance and so on. It is helpful to understand the response of the key mechanisms of soil greenhouse gas emission in the background of biological invasion, and helpful to provide theoretical and methodological support for studying the effects of invasive alien species on soil ecological processes, risk assessment and control technology.

温室气体排放和生物入侵作为广义上全球变化的两个重要内容一直受到关注。稻田土壤是温室气体甲烷和氧化亚氮的重要排放源，土壤动物对温室气体排放具有重要的调控作用。目前国内外大多数的相关研究主要集中在土著土壤动物造成的土壤性质变化及温室气体排放的影响方面，而对外来动物入侵影响土壤生态环境导致土壤温室气体排放及其过程变化的关注甚少。福寿螺是世界100种恶性外来入侵物种之一，2003年我国将福寿螺列入16种入侵外来物种的“黑名单”。福寿螺危害水稻生产，还会剧烈改变稻田生态环境，引起土壤状态变化。目前对适应强、生长快、体型大的福寿螺影响土壤温室气体排放转化过程的研究还十分缺乏，表现在活动行为、植株损伤、自身代谢及土壤扰动等方面。阐明福寿螺入侵对土壤温室气体排放过程的影响有助于了解在生物入侵背景下土壤温室气体排放过程的响应，为深入研究外来入侵动物影响土壤生态过程、风险评估与防控技术等提供理论与方法参考。

福寿螺是入侵华南地区的重要外来软体动物之一，其在稻田内已经建立了稳定的种群。稻田作为农业温室气体排放的重要源头，在外来物种福寿螺入侵40年来，稻田的水土环境、水稻和水生植物不可避免地受其影响。我们通过大田监测和室内模拟实验分析了福寿螺活动对稻田排放CH4和N2O的影响，在福寿螺种群密度、年龄、扰动土壤、摄食水稻、代谢活动等方面探索了其过程机制，并采用模型模拟了福寿螺入侵情形下稻田CH4和N2O的排放情况，结果表明：1)福寿螺入侵对稻田的CH4和N2O的影响存在密度和年龄效应，两种气体排放对福寿螺活动响应不同。福寿螺入侵存在降低CH4排放趋势，显著提高N2O排放。2)福寿螺活动改变了氮素含量，促进N2O排放；返青期后对水稻生长存在抑制效应，造成的生物损伤降低了CH4和N2O排放，且与福寿螺损伤强度有关。3)福寿螺的爬行促进N2O排放，高密度福寿螺爬行抑制CH4排放，扰动增加了土壤的养分含量和酶活性。福寿螺自埋行为受水质因子的影响，福寿螺休眠行为影响土壤N2O排放，改变螺触圈土壤的N2O排放特性。4)福寿螺排泄物和活动液体影响水稻生长，改变了水稻CH4和N2O的释放，排泄物促进N2O的释放，分泌物对反硝化菌存在抑制效应。福寿螺代谢过程存在N2O排放。采用STELLA-DNDC模型模拟发现福寿螺入侵导致稻田N2O排放的升高，对CH4排放有抑制作用。项目揭示了福寿螺在稻田内摄食、扰动、排泄、分泌行为影响土壤性质及微生物的温室气体排放过程，拟合证实了福寿螺入侵稻田显著改变CH4和N2O排放。研究结果为合理评估稻田CH4和N2O排放量以及福寿螺生态风险提供了坚实的依据。