干热河谷主要植被恢复树种蒸腾作用

以金沙江干热河谷区10多种自然生长树种为试材,探讨了不同季节典型晴天里各树种叶片水平的蒸腾速率日动态规律,以揭示极端干热生境条件下供试树种蒸腾作用的动态特征.实验结果表明:在干旱生境(3月份)转向干热生境(5月份)时,大多数供试树种蒸腾速率的日变化峰值有所提前,蒸腾作用受到明显限制,而当干热胁迫解除、湿润生境(10月份)来临时,蒸腾作用受限程度减轻或消失,多数供试树种呈现出比较典型的峰状曲线;在干旱、干热以及湿润季节里,供试树种均可分为高、亚高、亚低和低蒸腾速率树种等4个类别,且随着季节的变化,树种所属类别或蒸腾速率大小排序存在明显变动,体现了树种特性在水分生理反应上的多样性表达;随着干热胁迫的加深,供试树种蒸腾速率的变化可分为增强型、减弱型及稳定型3种;树种蒸腾速率的变化方向与气孔导度的变化方向存在不一致的现象,树种蒸腾速率的季节性增减可能表现为气孔因素为主与非气孔因素为主两种控制形式.

Transpiration of tree species for vegetation restoration in dry-hot river valleys

Transpiration of more than 10 tree species naturally occuring in the dry-hot valleys of Jinsha River was measured on typical sunny days in different seasons in order to reveal their dynamic patterns of transpiration under extreme dry and hot habitat conditions. During the transition period from dry in March to dry and hot in May, the daily peak time of transpiration rate of most tree species appeared ealier, indicating obvious transpiration depression. When drought and heat stress was relieved and wet season came, the transpiration depression became lightened or disappeared, and most tree species displayed typical peak-shape curves again. In drought, dry and hot and wet seasons, the tested species can be classified into 4 groups respectively with high, sub-high, sub-low and low average daily transpiration rate. The grouping of species and the ranks of transpiration rates displayed significant changes among different seasons, indicating diversified physiological responses to water stress. With intensified drought and heat stress, 3 patterns of change, enhanced, weakened and stable, were found of the transpiration rates. The direction of seasonal change of transpiration rate was inconsistent with that of stoma conductance, the seasonal change of transpiration rate was probably controlled by both stoma-related and non stoma-related factors.