土壤-玉米系统中土壤呼吸强度及各组分贡献

Soil respiration in a maize-soil ecosystem and contribution of rhizosphere respiration

用特殊设计的气体采集箱法对玉米生长期间潮土呼吸强度进行了测定。结果表明，施用150kgNhm^-2的裸地土壤CO2累积排放量是294g C m^-2，约为种植玉米土壤的一半。用根去除法测得的玉米对土壤呼吸的贡献率，苗期小于20％，拔节到收获期波动在30％-70％之间，全生长期平均为46％。玉米生长期间因土壤有机碳分解而释放出的CO2总量为2．94MgChm^-2，大约是0—40cm土层中土壤有机碳总储存量的8％，因此需要输入7．35Mghm^-2的碳含量40％的作物残留物才能平衡土壤中有机碳的损失，约为玉米收获时残留于土壤中根量的一倍，但与残留根量及玉米生长期间根系分泌到土壤的有机物量的总和相当，因此土壤中有机碳总体处于平衡状态。在玉米生长期间，施用氮肥可使土壤CO2排放量降低10％。土壤排放CO2主要受土壤温度的影响，温度效应Q10为1．90-2．88。

To evaluate soil CO2 emission and relative contribution of rhizospheric and soil respiration during the maize growing season, a field experiment was carried out in Fengqiu State Key Agro-Ecological Experimental Station, Henan Province, China in 2004.The experiment included four treatments： bare soil fertilized with 150 kg N hm^-2 and maize-cropped soil amended with 0, 150, and 250 kg N hm^-2 . The cumulative amount of CO2 emission in the bare soil fertilized with 150 kg N hm^-2 was 294 g C m^-2, about half of that from the soil fertilized with 150 kg N hm^-2 and planted. The mean ratio of rhizospheric respiration to total soil CO2 emission measured by root exclusion method was 46 %, but was below 20 % at the seedling stage and fluctuated between 30% and 70% at the other stages. Total amount of CO2 released from soil organic matter during the maize growing season reached 2.94 Mg C hm^-2, equivalent to 8% of the total carbon content in surface soil （0 -- 40 cm）. Our estimates indicated that 7.35 Mg hm^-2 plant residue with 40% carbon content was needed to supplement carbon loss as CO2, which was twice the magnitude of maize root biomass left in soil after harvest, but equaled to the amount of maize root biomass and root exudates. The application magnitude of N fertilizer did not affect soil CO2 emission. However, N addition strongly reduced soil CO2 emission in tested soil compared to treatments without N application. Soil CO2 emission was mainly affected by soil temperature rather than soil moisture with Q10 of 1.90-2.88.