土壤温度和水分对油松林土壤呼吸的影响

用LI-COR 6400-09土壤呼吸测定系统,在太原天龙山自然保护区对油松林的土壤呼吸进行了4a测定.结果表明,土壤呼吸具有明显的季节变化特点,最大值出现在8月份,在6～10 μmol m~(-2) s~(-1) 之间,最小值出现在12月份和3月份,在0.5 μmol m~(-2) s~(-1)左右.2005、2006、2007和2008年土壤呼吸CO_2的年平均值分别为(4.71±3.74)、(3.08±2.91)、(2.96±2.58) μmol m~(-2) s~(-1)和(2.12±1.54) μmol m~(-2) s~(-1);4a的CO_2总平均值为(3.27±2.95) μmol m~(-2) s~(-1).4个测定年土壤呼吸的平均值总体差异显著.4个测定年土壤CO_2释放C量分别为1103.5、882.8、918.4 g m~(-2)和666.3 g m~(-2),总C平均值为892.8 g m~(-2),具有明显的年际差异.指数方程可以很好的表达土壤呼吸与10 cm深度土壤温度的关系,R~2值4a分别为0.39,0.60,0.68和0.71,Q_(10)值分别为3.10,4.41、4.05和5.18,用4a全部数据计算的Q_(10)值为4.31.土壤水分对土壤呼吸的作用较弱,R~2值4a分别仅为0.31、0.25、0.13和0.02,但是夏季土壤干旱对土壤呼吸的抑制作用非常明显,可使土壤呼吸下降50%以上.夏季土壤干旱是导致土壤呼吸年际变化的主要原因.4个包括土壤温度和水分的双变量模型均可以很好地模拟土壤呼吸的季节变化, 拟合方程的R~2值从0.58到0.79.

Effect of soil temperature and moisture on soil CO2 efflux in a Pinus tabulaeformis forest

Soil respiration was measured in a pine (Pinus tabulaeformis) forest in Tianlong mountain area near Taiyuan city for a period of about four years from April 2005 to December 2008. The purpose was to investigate both seasonal and interannual variations and relationships between soil respiration and both soil temperature and soil moisture. The CO_2 efflux was found to exhibit pronounced seasonal variations mainly controlled by the soil temperature. The highest CO_2 efflux values were between 6 to 10 μmol m~(-2) s~(-1) in August whereas the CO_2 lowest values were about 0.5 μmol m~(-2) s~(-1) in winter and early spring. For the four years (2005-2008) the mean annual rate of soil respiration was (4.71±3.74), (3.08±2.91), (2.96±2.58)μmol m~(-2) s~(-1) and (2.12±1.54) μmol m~(-2) s~(-1), respectively. The four-years overall mean was (3.27±2.95) μmol m~(-2) s~(-1). The difference in the mean annual soil respiration for the four individual years was distinct. The cumulative annual respiration C was 1103.5, 882.8, 918.4 g m~(-2) a~(-1) and 666.3 g m~(-2) a~(-1), respectively, for the four years (2005, 2006, 2007 and 2008).The relationships between soil respiration and soil temperature at 10 cm depth could be described by exponential equation, with a determination coefficient (R~2) of 0.39, 0.60, 0.68 and 0.71, respectively, for 2005, 2006, 2007 and 2008. Compared hereto, the soil moisture dependence on soil respiration was less pronounced giving annual R~2-values of 0.31, 0.25, 0.13 and 0.02, respectively for the four years. This indicates that soil water content, taken on its own, was less effective than soil temperature to predict the annual course in soil respiration. In the summer months, however, distinct effect of drought was found to reduce the soil respiration by 50%. To be able to predict both the soil moisture and soil temperature dependency four two-variable linear/non-linear models were developed. By use of those models it was possible to predict the soil respiration as function of both temperature and soil moisture, with a R~2 ranging from 0.58 to 0.79.