中亚热带森林地表CH_4和N_2O通量影响因素分析

Effects of environmental factors on soil CH_4 and N_2O fluxes in three forest types in central subtropical China

中亚热带森林是我国重要而独特的植被类型。本研究以本区域中3种典型的林分类型—杉木人工纯林、马尾松+石栎针阔混交林、青冈+石栎常绿阔叶林为研究对象,采用静态箱法—气相色谱法分析地表温室气体CH_4、N_2O浓度,同时观测样地环境因子。运用典型相关分析方法分析地表温室气体通量与环境因子的相关关系,并且对环境因子进行主成分分析。结果表明:(1)从总体来看,中亚热带森林地表温室气体通量是受多因素综合作用的结果,林地温室气体通量与林地环境因子间存在显著相关性(P<0.05),二者间的相关性程度也因不同林型而异;(2)在诸多环境因素中,温度是其中的主导因子,对地表温室气体影响相对较大,尤其是地表和地下5 cm处土壤温度;(3)其它非生物因素(如土壤水分、土壤碳氮含量、坡位等)对温室气体通量所起作用的大小则因具体的林型而异;(4)生物因素中不同林型间地表温室气体通量存在显著差异(P<0.05);(5)不同林型地表温室气体存在明显的季节动态。

Forest stands surface greenhouse gas fluxes play a pivotal role in the global carbon balance and global climate change. Forests in central subtropical is an important and special vegetation type in China. The typical forest types including Chinese fir plantation, Pinus massoniana ＋ Lthocarpus glaber mixed forest, and Cyclobalanopsis glauca ＋ Lithocarpus glaber mixed evergreen broad-leaved forest were selected for the sampling plots using static chamber technique and gas chromatography analysis of soil surface greenhouse gases （CH4 and N2O）. The local environmental factors were recorded including soil surface temperature, soil temperature at 5 cm depth, air temperature, air temperature in the static chamber, soil moisture content in the field. And soil total organic carbon and soil total organic nitrogen were measured in the laboratory. The relationship between the greenhouse gas flux and environmental factors was analyzed by using the canonical correlation analysis （CCA） method. The principal component analysis （PCA） was carried out to investigate the dominant factors in all the environmental factors. Some conclusions were drawn as the followings： （a） in general, soil surface greenhouse gases in the forest stands were influenced by multiple environmental factors and eorrelationship between greenhouse gases and environmental factors was statistically significant at the level of 0.05 which varied with the forest types, （b） temperature was the dominant factor among the environmental factors which affects soil surface greenhouse gases, especially temperature at soil surface and 5cm depth, （c） the rest of physical environmental factors, such as soil moisture, soil carbon and nitrogen content, slope position also played an important role in greenhouse gases flux but the correlation coefficients varied with forest types, （d） the biological factor as forest types caused a statistical difference in soil surface greenhouse gases flux （P 〈 0.05）, and （e） seasonal dynamics in soil surface greenhouse gases flux was significant in the forest types.