中文摘要：

以种植了4个不同密度冬小麦的土壤为研究对象,在返青-拔节期应用根生物量外推法定量研究了土壤呼吸的各组分,即自养呼吸（根呼吸）和异养呼吸.2006年2月27日、3月6日、3月13日、3月20日4次的测定结果表明,土壤的异养呼吸速率分别为68.5,62.8,76.8,119.6mg.m^-2.h^-1;由于小麦生长的补偿效应使得不同种植密度下的根生物量差异减小,在3月27日的试验中,根生物量外推法不能确定出土壤异养呼吸的数值.进一步的分析结果表明,在每个采样日不同种植密度下的小麦根呼吸系数均无显著差异;而所有小麦种植密度的平均根呼吸系数随作物生长呈下降趋势.可将根呼吸系数（R rc）表示为根系氮含量（N）和土壤体积含水量（W）两因子的指数影响函数,其表达式为：R rc=0.001 e（0.375W＋5.503N）.式中,W,N分别为土壤体积含水量和根系氮含量,R rc为根呼吸系数,决定系数R2=0.966.应用根系氮含量和土壤湿度这两个因子可较好的模拟根呼吸系数的动态变化.对于与田间实际小麦种植密度接近的处理而言,在返青-拔节期根呼吸占土壤呼吸的比例在28%~81%之间变异.

英文摘要：

Soil respiration rate was measured in a soil-winter wheat system under four planting densities during the turning green-elongation periods. Soil autotrophic and heterotrophic respiration were partitioned using root biomass regression techniques. Soil heterotrophic respiration rates were measured weekly from 27 February to 20 March, 2006 and the average weekly rates were： 68. 5,62. 8,76. 8 and 119.6 mg·m^-2·h^-1. However, the soil heterotrophic respiration could not be determined based on the root biomass regression method on 27 March since the difference of root biomass was not pronounced among different planting densities at this period. Further investigation revealed that the root respiration coefficient under different planting densities had no significant differences on a given measurement date, but the root respiration coefficient decreased with crop growth. The variation of root respiration coefficient （Rrc） could be estimated by soil volumetric water content （W） and root total nitrogen content （N） using a statistical model （ Rrc = 0.00l e（0.375W ＋ 5.503N） ） , which can explain 96.6 % （ R2 = 0. 966） of its total variation. The results of this study using treatment similar to conventional field planting densities suggest that root respiration contributes 28%- 81% to the total soil respiration during the turning green-elongation periods.