土壤水分对夏玉米农田CO_2通量和群体水分利用率的影响

Influence of Soil Water on CO_2 Flux Density and Group Water Use Efficiency in Summer Corn Field

利用 Ｃ Ｏ２ 分析系统，配合波文比装置，在夏玉米全生育期连续测定农田冠层瞬时 Ｃ Ｏ２ 浓度差及农田小气候特征量，并计算了农田冠层瞬时 Ｃ Ｏ２ 通量密度、潜热通量和群体水分利用率。结果表明，群体光饱和点位移是受土壤水分影响的一个辐射能量范围，充沛的太阳辐射能量只有充足水分条件的耦合，才能发挥生产力效益；群体水分利用率与０～６０ ｃｍ 土层土壤平均相对含水率呈负相关，土壤相对含水率在３０３％ ～８０％ 范围内，水分利用率随相对含水率的增加而降低。

The instantaneous CO 2 flux concentration gradient 0 5 m and 2 0 m higher above the canopy was measured with an infrared CO 2 analysis system during the growing season of summer corn. The field microclimatic factors such as radiation, temperature and moisture were measured simultaneously using the Bowen ration device, and the CO 2 flux density, latent heat flux and water use efficiency were also calculated. The results showed that the CO 2 analysis system was effective as the CO 2 flux density had the same variation trend as dry matter, and it proved useful as an advanced method to calculate the water use efficiency. The relationship between net photosynthesis rate and global radiation can be expressed as parabolic equation. When radiation reaches the light saturation point, the net photosynthesis rate will not increase any more. The light saturation point was affected by soil water content, and the radiation energy can make productive effect only with the affluent soil water. There was negative correlation between group water use efficiency and the relative water content in 0~ 60 cm soil. When the relative water content was in the range of 30.3%~80%, the water use efficiency decreased with the increase of soil water content. Some measures can be taken to develop the root to absorb the deep soil water and can increase the water use efficiency while the water supply did not increase.