农林复合系统中南酸枣蒸腾特征及影响因子

Transpiration of Choerospondias axillaris in agro-forestrial system and its affecting factors

用热平衡法(Granier法)确定了南酸枣蒸腾量,研究了低丘红壤农林复合系统中南酸枣(Choerospondias axillaries)蒸腾的日变化特征、对复合利用方式及截枝处理的响应,并利用相关分析和多元逐步回归分析方法,探讨了影响蒸腾的因素.结果表明,蒸腾速率具有明显的早晚低、中午高的日变化特征,但在不同日期蒸腾速率日变化曲线存在一定差异,且在旱季晚间23:30后仍有茎流现象.南酸枣蒸腾主要受深层土壤水分的影响,与100 cm土壤深处的水势呈极显著正相关(R=0.737**).农林复合,通过树木对深层水分的利用及微区域环境的改变,提高了植物蒸腾量40%～160%,为实现水分高效利用提供了可能.在影响蒸腾作用的气象因子中,光辐射强度、气温、地温是主要因子,而空气饱和水汽压差和风速次之.最后给出了依据气象因子估算茎流流速的统计模型.

Measurement of transpiration is essential to assess plant water use efficiency. Applying Grainer method, this paper measured the sap flow of Choerospondias axillaries in an agro-forestrial system, aimed to evaluate the effects of intercropping and pruning on the diurnal variation of transpiration, and to relate the transpiration rate with climatic factors. The results showed that the diurnal variation of Choerospondias axillaries transpiration rate appeared in parabola, low in the morning and evening, and high at noon. The transpiration rate was closely related to leaf stomatal conductivity and soil water potential, especially the water potential in 100 cm soil depth（ R = 0. 737^＊＊）. The transpiration rate of Choerospondias axillaries was increased by about 40 % ～160 % in agroforestrial system through the changes in regional environment and in the deep soil water use by tree. Correlation analysis and multi-factor successive regression analysis indicated that the transpiration was controlled by ray radiation intensity, air temperature and ground temperature, followed by the difference between saturated and actual vapor pressure and the wind speed. A statistical model for calculating the sap flow rate by micrometeorological factors was also provided.