极端干旱区旱生芦苇叶水势变化及其影响因子研究

以新疆塔里木河下游绿洲-荒漠过渡带干旱环境下的旱生芦苇为研究对象,结合对气象因子、土壤水盐和芦苇叶水势的实地监测资料,分析了不同地下水埋深下芦苇叶水势的日变化特征,研究了影响芦苇叶水势变化的主导环境因子,揭示了反应芦苇叶水势变化的环境因子的指示性和指示阈值。结果表明,1)地下水埋深越下降,芦苇叶水势的日变化单峰趋势越不明显,表现为逐渐降低的变化趋势;2)随着地下水埋深的下降,0~110 cm土层土壤含水率逐渐减小,芦苇水平根分布深度逐渐下移;3)在极端干旱区,芦苇的生存策略为“较高的土壤水分有利于芦苇群落的扩展,较低的土壤水分则促进单棵芦苇的生长”。4) 土壤含水率和气温是影响干旱区旱生芦苇叶水势发生变化的主要因素,芦苇生长的适宜土壤水分范围为10%~20%,(18.07±5.28)%的土壤含水率和(33.48±1.44)℃的气温为影响芦苇叶水势发生变化的临界阈值,土壤含水率>(18.07±5.28)%和气温<(33.48±1.44)℃时,芦苇叶水势不发生显著变化。该研究可为减轻芦苇受旱程度、维持芦苇正常生长、及时补充水分提供理论依据。

Analysis on dominant factors influencing water potential of Phragmites australis in extremely arid areas

Phragmites australis grown in the transitional belt between the desert and oasis of dry areas in the lower reaches of the Tarim River in Xinjiang was studied.Meteorological factors,soil moisture,soil salt and leaf water potential of P.australis were measured to analyze daily changes of leaf water potential of P.australis grown with various depths of groundwater.Environmental factors dominating water potential were examined,and they indicated thresholds that reflected water potential changes.1) When the groundwater became deeper,the daily peak of leaf water potential was reduced;2) When the groundwater became deeper,the 0-110 cm soil layers became dryer,and P.australis horizontal roots distributed into deeper soil layers;3) In arid areas,the survival strategy of P.australis appeared to be "higher soil moisture benefits population expansion,while lower soil moisture promotes the height of individual plants";4) Soil moisture and air temperature were the dominant factors influencing the change of leaf water potential.P.australis prefers soil containing 10%-20% of water.The threshold of soil moisture at which leaf water potential changed was 18.07%,and the threshold of air temperature was 33.48℃.Leaf water potential did not change if soil water was>18.07% or air temperature was below 33.48℃.This study provides a theoretical basis for mitigating drought stress of P.australis and maintaining its normal growth.