植物和土壤的非微生物甲烷生成和排放

Methane may be produced via microbial and non-microbial mechanisms. Non-microbial methane is produced by an instant reaction of organic compounds under environmental stresses, without involving enzymatic catalysis of methanogenic archaea. In nature non-microbial methane production is more pervasive than what people previously thought, but it has received less attention relative to microbial methane production. The terrestrial ecosystems would have the mixed productions and emissions of microbial and non-microbial methane. However, both forms of methane are difficultly separated to understand in the field, it is essential to quantify non-microbial methane via simulated experiments in laboratory. Using tissue cell culture and two-room chamber, this proposed research will study non-microbial methane production and emission by model plants when the plants are exposed to the changing oxygen concentrations. Various oxygen conditions will be treated on plant roots, such as oxygen concentration, oxygen lasting time, and/or the alternation of aerobic versus anaerobic conditions, whereas plant stems and leaves are under the atmospheric oxygen concentration. Using PVC (polyvinyl chloride) mini-chamber technique, this proposed research will also study non-microbial methane production and emission by soil cores sampled in forests, graslands, farmlands, and wetlands. The effects of environmental stresses on the non-microbial methane in soils will be further investigated. On the basis of the measured results, we will evaluate the importance of non-microbial methane in terrestrial ecosystems.

甲烷可以通过微生物的和非微生物的机理而生成。非微生物甲烷是有机化合物在环境压力下的即时反应而产生的，不是甲烷古菌酶催化产生的。在自然界，非微生物甲烷比原先想象的要广泛；相对于微生物甲烷，非微生物甲烷受到较少的关注。陆地生态系统很可能存在微生物甲烷和非微生物甲烷的混合生成和排放。然而，在目前的认识和技术水平下，两者很难在野外被分开测定。为了认识非微生物甲烷，室内的模拟控制实验就很有必要。本项目以模式植物为对象，应用无菌苗培养和分室箱体等方法，对植物根系施加各种氧气浓度、氧气持续时间、有氧与厌氧交替等处理，而植物茎叶仍生长在稳定的大气氧气浓度下，研究植物茎叶和根系的非微生物甲烷生成和排放。本项目也以土壤柱为对象，应用PVC微型箱式法，调查森林、草地、农田和湿地的土壤非微生物甲烷生成和排放，进一步测定环境压力对土壤非微生物甲烷的影响。基于实验结果，本项目将评价陆地生态系统的非微生物甲烷的重要性。

甲烷可通过微生物的和非微生物的机理而生成。微生物甲烷是有机化合物在甲烷古菌酶催化下生成的，而非微生物甲烷是有机化合物在环境压力下的即时反应而生成的。陆地生态系统存在微生物甲烷与非微生物甲烷的混合生成和排放。在自然界，微生物甲烷得到广泛的调查，而非微生物甲烷受到较少的关注。然而，在目前的认识和技术水平下，两者很难在野外被分开测定。本项目以陆地树木为对象，应用野外定位和室内培养等方法，研究植物微生物甲烷和非微生物甲烷的生成和排放。实验结果表明，杨树树干排放大量甲烷，排放的甲烷生成于心材中，是通过微生物机理而生成的。在森林生态系统尺度上，年度树干甲烷排放量相当于土壤甲烷氧化量的三分之二。杨树心材水分含量在甲烷生成中起到至关重要的作用。本项目也以土壤为对象，应用野外取样和室内培养方法，调查森林、草地、果园、农田和湿地土壤微生物甲烷和非微生物甲烷的生成和排放，进一步测定环境因子对土壤甲烷的影响。实验结果表明，微生物甲烷排放主要发生在湿地土壤，而非微生物甲烷排放主要发生在旱地表层土壤并随温度增加而增加。在自然界温度变化条件下，非微生物甲烷排放占土壤总甲烷排放的比重较低。本项目也评价了陆地生态系统非微生物甲烷的重要性。