干热河谷区橙子树蒸腾耗水环境响应与生理调节研究

Environmental Response and Physiological Regulation of Transpiration Water Consumption of Orange Trees in Dry-hot Valley

为探究西南干热河谷地区典型经济林木橙子树的蒸腾耗水机制,利用热扩散式探针TDP、冠层分析仪、土壤水分传感器TDR、全自动气象站等设备获取橙子树蒸腾量、叶面积指数、土壤含水率和气象因子(气温、辐射、饱和水汽压差、降雨量等)的长期数据。对橙子树蒸腾规律的环境控制和生理调节特征进行系统研究,结果表明:相比于干季和雨季,干热季橙子树表现出较为保守的水分利用机制,日蒸腾量、冠层导度和退耦系数都显著低于其他两个季节。干季和雨季,橙子树蒸腾活动受太阳辐射和饱和水汽压差的交替控制,而干热季蒸腾活动主要受饱和水汽压差的驱动。冠层导度与气象因子日内动态变化特征之间存在时滞效应,且这种效应在不同天气不同季节具有差异。受叶面积指数影响,饱和水汽压差与冠层导度在整个年份呈负对数相关关系,其他环境因子与冠层导度在叶面积指数小于4 m^(2)/m^(2)时呈负对数相关关系,大于等于4 m^(2)/m^(2)时呈二次函数相关关系。不同环境条件下虽然冠层导度对饱和水汽压差的敏感性不同,但蒸腾耗水在大多数环境条件下基本遵循等水势调节策略,但个别环境条件下存在环境胁迫应对失衡风险。研究结果可为干热河谷区橙子园环境胁迫诊断提供直接依据,有利于灌溉制度的科学优化和节水调控技术体系的高效制定。

In order to investigate the transpiration and water consumption mechanism of orange trees,a typical economic forest tree in dry-hot valley region of Southwest China was taken as object,and the thermal diffusion probe TDP,soil moisture sensor TDR,automatic weather station and canopy analyzer were used to obtain long-term data on transpiration,soil water content,and temperature,radiation,vapor pressure deficit,precipitation and leaf area index.Through a systematic study on the environmental control and physiological regulation of orange transpiration,the results showed that compared with the dry season and rainy season,the dry-hot season showed a more conservative water utilization mechanism,and the daily transpiration,canopy conductivity and decoupling coefficient were significantly lower than those of the other two seasons.In the dry season and rainy season,the transpiration of orange trees was alternately controlled by solar radiation and the vapor pressure deficit,while the transpiration in the dry-hot season was mainly affected by the vapor pressure deficit.There was a time lag effect between the intraday dynamic change characteristics of the canopy conductance and meteorological factors,and this effect varied in different weather and seasons.The vapor pressure deficit was negatively logarithmically correlated with canopy conductance as influenced by the leaf area index,and other environmental factors also were negatively logarithmically correlated with canopy conductance at leaf area indexes less than 4 m^(2)/m^(2) and quadratically correlated at greater than or equal to 4 m^(2)/m^(2).Although the sensitivity of canopy conductance to saturated water vapor pressure difference varied under different environmental conditions,transpiration basically followed the isohydric regulation strategy under most environmental conditions,but there were individual environmental conditions presenting the risk of environmental stress imbalance.The results can provide a direct basis for the diagnosis of environmental stress in orange orchards in the dry-hot valley area,which was conducive to the scientific optimization of irrigation systems and the efficient formulation of water-saving regulation technology system.