中文摘要：

采用涡动相关法对张掖灌区玉米农田生态系统生长季（6—9月）CO2通量进行了连续观测,分析了玉米农田生态系统CO2通量变化特征及其对环境的响应。结果表明：CO2通量具有明显的日变化特征,白天以碳吸收为主,夜间以碳排放为主,CO2吸收的最大值出现在灌浆期,峰值为-1.426 mg·m^-2·s^-1;农田生态系统在4个生育期均表现为碳吸收,但吸收CO2能力存在显著差异,日吸收总量灌浆期〉拔节期〉成熟期〉苗期。利用Michaelis-Menten方程和指数曲线拟合方法,分别分析了光合有效辐射对白天CO2通量的影响,及温度对夜间生态系统呼吸的影响。结果表明：白天CO2吸收强度随着光合有效辐射的增大而增大,在低光阶段,光照是控制光合作用的主导因子,之后随着光合有效辐射的增大,净吸收量增加减缓;玉米的光量子利用效率变化范围为0.00098～0.0022 mg·μmol^-1。夜间生态系统呼吸与温度呈显著的指数关系,不同生育期的主导因子不同,苗期土壤温度是主导因子,其余生育期气温是主导因子。

英文摘要：

CO2flux was measured continuously in a maize agroecosystem in Zhangye irrigation area during the growing season（June to September） using the eddy covariance technique to study the variation of CO2flux and its response to key environmental factors. The results showed that there was a distinct diurnal variation of CO2flux,with CO2absorption in the daytime and emission at night. The maximum CO2absorption occurred at filling stage and with a maximum value of- 1. 426 mg·m^- 2·s^- 1. Maize agroecosystem is characterized by carbon absorption during the growing season,and the ability to absorb CO2is significantly different at different growth stages,which was ordered as filling stage 〉jointing stage〉 maturity stage〉 seedling stage. We also used the Michaelis-Menten equation and exponential curve fitting method to analyze the impact of photosynthetically active radiation（PAR） on daytime CO2flux,and the impact of temperature on the ecosystem respiration at night. The results showed that CO2absorbing intensity increased with PAR. PAR was the dominant factor to control photosynthesis under low solar radiation,and the carbon assimilation rate increased slowly under high solar radiation. The light quantum efficiency of maize ranged between 0. 00098 and 0. 0022 mg·μmol^- 1during the observing period. The nighttime ecosystem respiration exponentially increased with temperature,and the dominant factor varied with growth stage. Soil temperature was the dominant factor of nighttime ecosystem respiration at the seedling stage,while air temperature was the dominant factor at the other growth stages.