作物生长和氮含量对土壤-作物系统CO_2排放的影响

CO_2 Emission from Soil-Crop System as Influenced by Crop Growth and Tissue N Content

为探讨作物生物学特征对土壤 作物系统CO2 排放的影响 ,本研究基于逐步收割法和静态暗箱 气相色谱技术 ,以冬小麦和水稻作物为研究对象 ,采用盆栽和大田试验的方法 ,在作物生长的主要生育期原位测定了土壤 作物系统CO2 排放速率 ,同时测定了作物生物量和氮含量 .研究结果表明 :①土壤 作物系统CO2 排放在生长季内呈现动态变化 ,土壤 水稻系统CO2 排放高于土壤 冬小麦系统 .②作物暗呼吸速率与生物量呈显著线性相关 .③作物暗呼吸系数 (Rd)的季节变化可以用植株氮含量来描述 .冬小麦Rd 与N含量的关系可用线性方程Rd=0 0 12 4N - 0 0 0 76 (R2 =0 9879,p <0 0 0 1)表示 ;水稻Rd 与N含量的关系可用二次方程Rd=0 0 0 85N2 - 0 0 0 4 9N(R2 =0 9776 ,p <0 0 0 1)表示 .④作物根系的参与极大地促进了土壤呼吸 .冬小麦生长季土壤表观呼吸CO2 平均值为 2 4 7 2mg·(m2 ·h) -1,高于未种作物土壤 1 78倍 ,水稻生长季为 2 15 3mg·(m2 ·h) -1CO2 ,高于未种作物土壤的 3 38倍 .冬小麦根系呼吸系数大于水稻 ,其根际呼吸对土壤表观呼吸的贡献高于水稻 .

To understand the CO 2 emission from soil-crop system as influenced by crop growth and tissue N content, pot and field experiments were carried out during 2001-02 wheat and rice growing seasons. Black chambers were used to take gas samples within a closed soil-crop system. The CO 2 emission rate was detected by a gas chromatograph. Seasonal change of the CO 2 emission was observed from the soil-crop system. Respiration from the soil-rice system was higher than that from the soil-wheat system. Dark respiration of the crop shoot was positively correlated to the shoot biomass. The respiration coefficient R d, defined as the amount of CO 2-C respired by per unit biomass C within one day under a reference temperature of 25℃, can be well quantitatively expressed by shoot N content for either wheat or rice crop. Relationship between the R d and the N content can be described as a linear regression of R d=0.0124N-0.0076(R2=0.9879,p<0.001)for the wheat crop and as a quadratic equation of R d=0.0085N2-0.0049N(R2=0.9776,p<0.001)for the rice crop, respectively. The crop roots promoted the soil respiration greatly, which increased by 178% for the wheat and 338% for the rice in comparison with the respiration from root-free soil. A further calculation of the root respiration, including root autotrophic respiration and rhizosphere respiration, suggested that the contribution of crop rhizosphere respiration to the total soil respiration was greater in the upland soil than that in the irrigated paddy soil.