森林生态系统土壤CO_2释放随海拔梯度的变化及其影响因子

Soil CO_2 emission distribution along an elevation gradient and the controlling factors in the forest ecosystem

联合国气候框架公约的签署提升了人们对全球变暖、碳循环的关注。土壤CO2释放作为土壤-大气CO2交换的主要途径之一,成为了各国生态学家研究的重点内容。通过对1800～2155m海拔梯度上森林生态系统土壤CO2释放进行研究,揭示了较小空间尺度上土壤CO2释放的变化规律及其控制机制。在研究区域内,随着海拔梯度的增加,森林土壤CO2释放由(1.94±0.06)μmolm-2s-1逐渐增加至(2.22±0.07)μmolm-2s-1。土壤温度、土壤水分、土壤有机碳(SOC)、全N、全P与土壤CO2释放呈显著正相关(n=14,P<0.05);土壤容重与土壤CO2释放速率呈显著负相关(n=14,P<0.05);土壤pH对土壤CO2释放影响不显著。作为一个复杂的生态学过程,环境因子及其交互作用对土壤CO2释放产生影响,为了减少因子共线性影响,逐步降低因子维数,采用主成分分析(PCA)揭示了土壤温度、土壤水分、SOC、全N、全P、容重6个因子的联合作用,其累积贡献率达到了57%以上;进一步运用逐步回归分析方法,探讨了影响土壤CO2释放沿海拔梯度分布的主导因子,结果表明土壤水分是研究区域森林生态系统土壤CO2释放沿海拔梯度变化的主导因子。

The observed increase in levels of atmospheric CO2 and the signing of the UN Framework Convention on Climate Change have increased interest in the global warming and the global carbon cycle. As one of the key components in the global carbon cycle, the response of soil carbon pool to the global warming is another studied focus issue. Changes in soil CO2 emission along the elevation gradient could reflect the outcome of multiple interacting environmental factors on a long temporal scale and a small spatial scale, therefore, a research focused on the variation of soil CO2 emission along 1800 -2155m elevation gradient and the response of it to controlling factors was carried out. In the study area, soil CO2 emission increased from （1.94 ± 0. 06） μ mol m^-2s^- 1 to （2.22 ± 0. 07） μ mol m^-2s^-1 along the elevation gradient, which was due to the responses of the controlling factors to the elevation. However, not only the effect of controlling factors can interact, overlap, or restrain each other, but also each factor can act in different ways. Soil temperature, soil moisture, SOC, total N and total P significantly correlated to soil CO2 emission positively （ n = 14, P 〈 0.05 ）, and soil bulk density correlated to soil CO2 emission negatively （ n = 14, P 〈 0.05 ）, whereas pH did not control soil CO2 emission significantly in this study. Moreover, a variety of statistical approaches were used to characterize the primary controls over soil CO2 emission among these controlling factors. Primary component analysis （PCA） explored data reduction and a stepwise regression analysis constructed a most parsimonious model of soil CO2 emission, in which the most obvious effect of soil moisture appeared to be as a primary constraint on the distribution of soil CO2 emission along the elevation gradient.