蚂蚁筑巢定居对热带森林土壤氧化亚氮(N2O)排放的影响及其机制

The tropical forest is an important source of soil N2O emission. The ant in the tropical rain forest of Xishuangbanna is the most abundant in China, and the nesting activity and settlement of ant in the forest affects soil microbial biomass and diversity, and soil physicochemical environment, which can regulate soil microbial ecology processes such as N mineralization, nitrification and denitrification. Therefore, this can have a crucial influence on the soil N2O emission. Four tropical forests at different succession stages are to be sampled for experiment to examine the effect of ant diversity and ant mound distribution on soil N2O emission; We will compare the soil N2O emission from the soils of ant nest and near the nest, and to analyze the effects of soil physicochemical properties and soil microbial change caused by the ant nesting activity on the soil N2O emission; Soils from ant nest and near nest are to be collected to explore the impact of ant nesting on soil N mineralization and that of N mineralization on the release of nitrification/denitrification substrate; We will also distinguish the change contribution of soil nitrification and denitrification on soil N2O emission under the nesting activity. Therefore, the results can determine the effect mechanism of ant nesting activity and settlement on soil N2O emissions in the Xishuangbanna tropical forests.

热带森林是土壤氧化亚氮（N2O）的重要排放源。西双版纳热带森林是我国蚂蚁分布最丰富的区域，蚂蚁筑巢定居通过影响巢穴地土壤微生物生物量、微生物多样性及土壤理化环境，调控N矿化、硝化/反硝化等土壤生物与生态学过程，从而影响土壤N2O的排放。以不同演替阶段4种热带森林为研究样地，研究蚂蚁多样性与蚁丘分布对土壤N2O排放的影响；原位测定蚂蚁巢穴与非巢地土壤N2O排放，并分析蚂蚁引起土壤理化性质及微生物改变对N2O排放的影响；研究蚂蚁对土壤N矿化的影响以及N矿化对硝化/反硝化底物释放的调控；研究蚂蚁引起土壤硝化/反硝化的改变对N2O排放的影响。通过以上研究，试图揭示蚂蚁筑巢定居影响热带森林土壤N2O排放的生态学过程及机制。

N2O是导致全球变暖的三大主要温室气体之一。热带森林土壤是大气N2O的一个重要排放源，探明热带森林N2O排放规律是全球变化研究的重要组成部分。目前，土壤N2O排放的影响研究主要集中于非生物因素，而关于土壤大型动物-功能微生物耦合而调控N2O排放动态的认识，仍然相当模糊。该项目以西双版纳不同恢复阶段热带森林为研究样地，阐明了蚂蚁多样性、蚁丘分布、硝化/反硝化微生物多样性、土壤N矿化及理化性质对N2O排放的影响机制。. 主要研究发现包括：1）土壤N2O排放速率随热带森林恢复呈现先增后减且在恢复后期趋于稳定的变化规律；相较于非巢地，蚂蚁筑巢提高N2O排放速率达1.4-1.6倍；捕食性横纹齿猛蚁巢穴N2O排放通量分别是植食性卡泼林大头蚁和腐食性邻巨首蚁的2.68倍和3.15倍。2）蚂蚁多样性与蚁丘分布格局显著影响土壤N2O排放动态。蚂蚁种类数、个体数、蚁巢密度、盖度、Shannon多样性与N2O排放显著正相关（r=0.63~0.97, p <0.05或0.01）。3）蚂蚁筑巢显著影响土壤功能微生物群落结构及多样性。蚂蚁活动引起硝化/反硝化功能微生物种类数、相对丰度及多样性变化对N2O排放的贡献率为62~92%，最大值出现恢复中期。4）蚂蚁筑巢显著增加热带森林土壤异质性而促进N2O排放。蚂蚁筑巢提高31~136%的土壤微生物量碳及碳氮养分含量、降低6%-45%的pH和容重，对N2O排放贡献达（44~96%）；其中捕食性横纹齿猛蚁具有最大贡献。5）蚂蚁筑巢提高不同恢复阶段热带森林土壤N矿化速率达3.31~4.88倍；捕食性横纹齿猛蚁（4.12-5.24倍）对N矿化贡献显著高于植食性卡泼林大头蚁与腐食性邻巨首蚁；土壤N矿化解释了89.6%的N2O排放变化。6）土壤反硝化作用（57~62%）对N2O排放贡献率显著高于硝化作用（38~43%）；蚂蚁筑巢对硝化的N2O排放提高率达16~44%、对反硝化的N2O排放提高率达30~60%；不同食性蚂蚁对硝化/反硝化N2O排放的贡献率通常表现为：捕食性横纹齿猛蚁>植食性卡泼林大头蚁>腐食性邻巨首蚁。.综上，蚂蚁筑巢通过改变土壤功能微生物多样性及理化状况，进而调控硝化与反硝化过程的N2O排放。研究成果有助于准确量化土壤大型动物对不同恢复阶段热带森林养分循环及温室气体排放的贡献，能为温室气体国家清单编制及政府参与国际气候谈判提供关键数据。

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