环境因子对兴安落叶松林生态系统CO2通量的影响

采用涡度相关技术,研究了主要环境因子与兴安落叶松林生态系统CO2通量的关系。结果表明: 1)生长季,CO2通量表现出较显著的日变化特征,白天为碳吸收阶段, 12:30—13:30 CO2通量吸收出现峰值,而夜间为碳排放阶段,昼夜CO2通量变化幅度在-1.09~0.11mg/(m2·s)之间,生态系统整体表现出较强的碳汇特征;非生长季,昼夜CO2通量变化幅度在0~0.3mg/(m2·s)之间,生态系统整体表现为碳源。2)生长季光合有效辐射(PAR)与CO2通量呈对数相关(R2=0.4861),随PAR增强,生态系统碳汇能力增大,PAR是CO2通量的直接影响因子;非生长季CO2通量与PAR相关性不显著。3)在生长季,兴安落叶松林CO2通量与气温(ta)有很好的相关性,决定系数R2为0.6272,CO2通量随ta的升高而降低,ta是兴安落叶松林生态系统CO2通量的主要限制因子;非生长季的12月至次年2月份,气温的变化对CO2通量无显著作用。4)土壤温度(ts)和含水率(RH)对CO2通量的影响,主要体现在生态系统呼吸(Re)上,兴安落叶松林生态系统的土壤含水率在62%~87%之间,土壤含水率达到67%以上时,CO2通量基本上不受土壤水分大小的影响。在水分不成为CO2通量限制因子的情况下,土壤温度对兴安落叶松林生态系统CO2通量影响起主要作用,研究表明:土壤温度与CO2通量呈指数相关(生长季R2=0.2826,非生长季R2=0.2223);即在适当的温度范围内,土壤温度的升高会加速植物和微生物的代谢,从而增强森林生态系统的呼吸作用,促进CO2排放。 

Impact of climate factors on CO2 flux characteristics in a Larix ;gmelinii forest ecosystem

Using the open path eddy covariance technique, we measured and analyzed the CO2 flux characteristics related to climate variables in a Larix gmelinii forest ecosystem ( hereinafter referred to as“the ecosystem”). The results showed that:1) In the growing season, the ecosystem CO2 flux changes with a diurnal cycle. The system assimilates CO2 in daytime and releases CO2 at night. The assimilation reaches its peak between 12:30 and 13:30. The CO2 flux ranges from -1. 09 to 0. 11 mg/( m2·s) during the day. In the non-growing season, the ecosystem shows a carbon source with the CO2 flux ranging from 0 to 0. 3 mg/(m2·s). 2) In the growing season, there is a logarithmic relationship between the CO2 flux and photosynthetic active radiation ( R2 =0. 486 1 ) , and the carbon sequestration capacity increases with the enhancement of PAR; therefore, PAR is a factor affecting CO2 flux directly. In the non-growing season, such relationship is not significant. 3 ) The CO2 flux is well correlated with air temperature ( ta ) in growing seasons ( R2 = 0. 627 2 ) , and CO2 flux is reduced with the rising ta , suggesting that ta is a main limiting factor in the ecosystem. In the non-growing season from December to February, the change of air temperature has no significant effects on CO2 flux. 4) The influence of soil temperature (ts) and soil moisture content (RH) on CO2 flux is mainly reflected in ecosystem respiration (Re). The soil moisture content ranges between 62% -87% in the ecosystem, with an average of 84%in the growing season and 67% in the non-growing season. Soil moisture content is not the main factor limiting CO2 flux in the ecosystem. On condition that water is not the limiting factor, soil temperature plays the major role on regulating CO2 flux in the ecosystem. Our research shows that there exists an exponential relationship between CO2 flux and soil temperature ( R2 =0. 282 6 in growing season and 0. 222 3 in non-growing season) . Within a certain range, the rise of soil temperature will accelerate the metabolism of plants and microorganisms, and thus enhance the respiration of forest ecosystem and promote the emission of CO2 .