CO2浓度增加对半干旱区春小麦生产和水分利用效率的影响

为了解CO₂浓度升高条件下春小麦生产和水分利用效率(WUE)的响应特征,在典型半干旱区定西,利用开顶式气室(OTC)试验平台开展了CO₂浓度增加模拟试验.试验设对照(390 μmol·mol^-1)、480 μmol·mol^-1和570 μmol·mol^-1 3个CO₂浓度.结果表明: CO₂浓度升高使春小麦冠层空气温度小幅上升,10 cm深处的土壤环境温度下降;CO₂浓度增加对春小麦各器官生物量和总生物量都有明显促进作用,在480和570 μmol·mol^-1浓度下,地上干物质量平均增长20.6%和41.5%,总干物质量平均增长19.3%和39.6%.生物量增加主要是由茎叶干物质量增加所致,与生育中期物质生产能力明显增强有关;在两种CO₂浓度处理下,植株根冠比分别降低7.3%和11.8%,CO₂浓度增加对春小麦地上部分干物质积累的贡献大于地下部分;CO₂浓度升高主要通过影响穗粒数来影响最终产量,在480和570 μmol·mol^-1浓度下,小麦产量分别增加了8.9%和19.9%;大气CO₂浓度升高对春小麦光合作用影响的长期效应不明显,随CO₂浓度升高,光合速率显著提高,蒸腾速率降低,蒸发蒸腾量减小.随CO₂浓度升高,叶片、群体和产量3个水平的WUE都增加,其中群体水平的WUE增幅最大,产量水平的WUE增幅最小.

Effects of elevated CO2 concentration on production and water use efficiency of spring wheat in semi-arid area.

In the present study, the response of spring wheat production and water use efficiency (WUE) to the elevated CO₂ concentrations was investigated based on the open-top chamber (OTC) experiment platform in Dingxi, a typical semi-arid area. Three different CO₂ concentrations (390 μmol·mol^-1, 480 μmol·mol^-1 and 570 μmol·mol^-1) were involved. The results showed that the air temperature above plant canopy increased and the soil temperature at depth of 10 cm decreased by elevated CO₂. The increased CO₂ concentration substantially enhanced the total and each component biomass. The aboveground dry mass under the increased CO₂ concentrations (480 and 570 μmol·mol^-1) was increased by 20.6% and 41.5%, respectively, and the total dry mass was increased by 19.3% and 39.6%, respectively. The biomass enhacement was mainly due to the increases of dry mass of stems and leaves, which was strongly related to the material production capacity during the middle growth stage. The root/shoot ratio under the increased CO₂ concentrations (480 and 570 μmol·mol^-1) was decreased by 7.3% and 11.8%, respectively, indicating that the elevated CO₂ affected the dry matter accumulation of aboveground more than that of belowground. The yields of spring wheat under the increased CO₂ concentrations (480 and 570 μmol·mol^-1) were higher than that of the control by 8.9% and 19.9%, respectively, mainly due to the increase of grains per spike. The long-term effect of elevated CO₂ concentration on the photosynthesis of spring wheat was not obvious. The photosynthetic rate significantly increased, the transpiration rate decreased and the evapotranspiration reduced with the increases of CO₂ concentration. WUE at the leaf, population, and yield levels increased under elevated CO₂ concentration, with the increase range of WUE being the largest at the population level and the lowest at the yield level.