冬小麦水分利用效率及其环境影响因素分析

WATER USE EFFICIENCY IN WINTER WHEAT FIELD AND ENVIRONMENTAL INFLUENCE ON IT

１９９６年４月～６月在华北平原采用波文比－能量平衡法测定冬小麦田蒸散和ＣＯ２通量，求取冬小麦瞬时水分利用效率。土壤湿度较低时，冬小麦瞬时水分利用效率呈Ｌ型或Ｕ型日变化，其变化范围在－０．０１９４～０．６４１４；日较差范围在０．１１３８～０．６３２１。瞬时水分利用效率早晨最高且变化迅速，白天较低且变化平缓。土壤湿度较高时，瞬时水分利用效率范围在－０．０１５７～０．１３８１；日较差范围在０．０６１６～０．１５３７，其日变化不明显。从冬小麦拔节期到灌浆期，水分利用效率白天平均值变化较大，其范围在０．０１１０～０．０５３２，日较差变化范围在０．０６１６～０．６３２１，二者均于５月中旬达到最高，之后在波动中呈下降趋势。冬小麦水分利用效率白天平均值和日较差的季节变化明显受土壤水分影响。冬小麦水分利用效率白天平均值与０ｃｍ～６０ｃｍ的有效土壤水分呈负相关，达到０．０５显著水平；与０ｃｍ～２０ｃｍ和０ｃｍ～１００ｃｍ土层土壤有效水分无明显相关关系。冬小麦瞬时水分利用效率与饱和差呈极显著负相关，达到０．０１显著水平。土壤湿度较低时二者呈幂相关关系；土壤湿度较高时二者呈线性相关，且相关系数比土壤湿度低时高。在低土壤含水量下，冬?

Evapotranspiration and CO 2 fluxes were measured using Bowen ratio energy balance method in winter wheat field in North China Plain from April to June 1996 and instantaneous water use efficiency ( WUE ) was obtained. L shaped or U shaped diurnal variation of WUE was found when soil moisture was low. Instantaneous WUE varied from 0.0194 to 0.6414. It was high and decreased quickly in the morning. It was low and stable during the daytime. The range of daily difference of WUE was from 0.1138 to 0.6321. When soil moisture was high, no obvious diurnal variation of WUE was found. Instantaneous WUE varied from -0.0157 to 0.1381. The range of daily difference of WUE was from 0.0616 to 0.1537. The seasonal variation of WUE was obviously and influenced by soil moisture. From elongation stage to milking stage in winter wheat field, Average of daytime's WUE varied from 0.0110 to 0.0532. Daily difference of WUE varied from 0.0616 to 0.6321. Both highest values were found in May, 13. Average and daily difference of WUE fluctuated and decreased in milking stage. Negative correlation between average of WUE and available soil moisture in the depth of 0 cm^60 cm was significant at 0.05 level. No remarkable correlation was found between average of WUE and available soil moisture in the depth of 0 cm^20 cm and 0 cm^100 cm. Negative correlation between Instantaneous WUE and saturation deficit was significant at 0.01 level. It was power regression between them when soil moisture was low. It's linear regression between them when soil moisture was high. Positive correlation between Instantaneous WUE and CO 2 mixing ratio above winter wheat canopy was significant at 0.01 level when soil moisture was low.