红壤丘陵区典型土地利用转变对土壤温室气体交换过程的影响研究

Land use/cover pattern have been dramatically changed due to the growing human population and activities during last decades, which in turn have significant impact on the soil-atmosphere exchange of CO2, CH4, N2O and NO and the key processes of soil carbon and nitrogen turnover. Currently, most of the existing related studies were focused on the differences of greenhouse gas fluxes among different land use types. However, very little is known about the dynamic and correlations among multiple kinds of greenhouse gases, and their coupling mechanism with the key processes of soil carbon and nitrogen turnover during the land use conversion. In this study, therefore, a small catchment-Qianyanzhou in typical hilly red soil region of Jiangxi province is selected as the key study area. Based on in situ land use conversion experiments, soil-atmosphere exchange of 4 kinds of carbon and nitrogen gases (CO2, CH4, N2O and NO) and the key processes of soil carbon and nitrogen turnover rates will be observed simultaneously, as well as the environmental parameters. By using these dataset, the main objectives of this study are: (1) to reveal the effects of typical land use conversion on the seasonal and annual dynamics of CO2, CH4, N2O and NO fluxes between soil and atmosphere, and their coupling mechanism with the key processes of soil carbon and nitrogen turnover; (2) to assess the impact of environmental factors and soil parameters on these gases fluxes during the whole period of land use conversion; (3) to determine the responding mechanisms of CO2, CH4, N2O and NO fluxes and soil carbon and nitrogen turnover processes to different types of land use conversion. These results are expected to provide scientific references for evaluating the combined effects of land use change on the soil-atmosphere exchange of greenhouse gases in the hilly red soil region of Southern China and forecasting the response to future land use changes.

随着人类活动的不断加剧，土地利用格局会发生显著的改变，这将进一步对土壤CO2、CH4、N2O和NO等碳氮气体交换以及碳氮循环关键过程产生深远的影响。目前，已有的相关研究大多是比较几种不同土地利用方式下土壤温室气体的差异，而对土地利用转变过程中多种温室气体交换规律动态变化以及与碳氮循环过程之间相互耦合的研究仍十分缺乏，导致对其交换特征与内在机制尚不明晰。本项目以江西省千烟洲流域为研究区，通过开展土地利用转变野外控制试验，同步观测4种碳氮气体和碳氮循环关键过程，从而揭示红壤丘陵区典型土地利用转变对土壤碳氮温室气体交换特征和土壤碳氮循环关键过程的综合影响，解析影响效应的时间变化格局和关键驱动因素，明确不同土地利用转变类型对地气交换与碳氮循环过程的影响规律与机制，从而为科学评估我国红壤丘陵区典型土地利用转变对土壤温室气体影响的综合效应以及为预测其对未来土地利用变化的响应提供科学依据。

本项目根据计划任务书的设计方案，依托中国科学院千烟洲生态试验站，以我国南方红壤丘陵区典型的土地利用方式转变方式—水稻田转为柑橘园为研究对象，采用静态箱-气相色谱法和化学发光法对土壤CH4，CO2，N2O和NO的通量进行了为期3年的连续监测，重点研究了水稻田转为柑橘园土壤温室气体通量变化，并分析了年际通量变化特征及其主控因子。同时结合分子生物学方法，分析了水稻田转柑橘园以及施肥对土壤微生物丰度，结构及多样性的变化影响，并从机理上探讨了土地利用转变和施肥对土壤CH4和N2O等温室气体通量的影响。主要的研究结果有以下几点：.1）在三年的连续观测中，水稻田土壤的CH4和N2O年均累计排放量分别为303.9 kg C ha-1和3.8 kg N ha-1。 尽管水稻田转变为柑橘园后，土壤年均N2O排放量增加了2-3倍，但土壤CH4排放量的大幅度减少甚至转变为大气CH4的吸收汇，导致柑橘园中CH4和N2O的综合增温潜势显著降低。此外，在土地利用转变的初始阶段，柑橘园土壤仍为CH4的弱排放源，并在转变后持续数周。在该地区由水稻转变为柑橘园不仅能产生更高的经济效益，同时导致土壤CH4和N2O的总排放量显著降低。.2）土地利用转变和施肥显著影响土壤产甲烷菌和甲烷氧化菌的丰度和群落结构。水稻田转柑橘园显著降低了土壤产甲烷菌和甲烷氧化菌丰度，但施肥对水稻田和柑橘园土壤产甲烷菌和甲烷氧化菌无显著影响。水稻田转柑橘园降低了土壤产甲烷菌的多样性，但增加了土壤type II 甲烷氧化菌。.3）在该红壤丘陵区，土壤AOA的数量明显高于AOB的数量。水稻田向柑橘园的土地利用转变增加了土壤AOA的丰度，对AOB 丰度无显著影响。对AOA和AOB的群落结构分析表明，土地利用转变改变了土壤AOA和AOB的群落结构。并且，水稻田转变为柑橘园降低了土壤反硝化微生物（nirK, nirS, nosZ）丰度，但施肥对反硝化微生物丰度无显著影响。.项目在Applied Soil Ecology，Scientific Reports，Environmental Science and Pollution Research，European Journal of Soil Biology等重要国际期刊发表了5篇论文，还有1篇SCI论文尚在审稿中，完成了任务书指标。