毛乌素沙地降水格局变化对油蒿木质部解剖特征的影响

探究不同降水处理对荒漠植物木质部解剖特征的影响，可以为理解未来降水格局变化下荒漠植物适应性和预测荒漠植被演替趋势提供理论依据。以毛乌素油蒿灌丛植被为对象，通过野外人工控制降水的方法，模拟半干旱气候区降水格局变化趋势，设置3个降水量梯度（减水30%、自然降水、增水30%）以及2个降水间隔梯度（降水间隔5d、降水间隔15d）开展双因素完全随机试验，监测油蒿木质部各个解剖特征参数对不同降水处理的响应。结果表明：（1）随着降水量减少，油蒿的导管数量显著增多，导管密度、导管壁厚度显著增大（P<0.05）。降水间隔时间延长将显著增加油蒿的导管数量、导管密度和平均导管直径（P<0.05）。降水量与降水间隔期对油蒿木质部解剖学特征影响的交互效应不显著。（2）降水量减少和降水间隔时间延长弱化了油蒿潜在最大导水率对导管直径的响应敏感度。（3）在降水量减少和延长降水间隔时间的背景下，油蒿可以通过调整木质部导管参数兼顾水分运输的安全与效率。本研究表明，通过改变木质部解剖学特征参数来适应降水格局改变是油蒿的重要耐旱策略，未来气候变化的大背景下，荒漠植物的水力特征变化需要综合考量降水量和降水间隔的双重影响。

Influence of changing precipitation patterns on the xylem anatomical characteristics of Artemisia ordosica in Mu Us Sandy Land

Investigating the effects of different precipitation treatments on xylem anatomical characteristics of desert plants can provide a theoretical basis for understanding the adaptation mechanism and predicting the desert ecosystem process responses to precipitation change in the future. In this study, we simulated the precipitation change in semi-arid climate zone by artificial precipitation controlling experiment in the desert ecosystem established mainly by Artemisia ordosica in Mu Us Sandy Land. A two-factor completely randomized experiment was conducted with three precipitation gradients (Precipitation reduce by 30%, natural precipitation, and Precipitation increase by 30%) and two precipitation interval gradients (precipitation interval 5 days and precipitation interval 15 days). The response of various anatomical characteristic parameters of the xylem of A. ordosica to different precipitation were monitored. The results indicated that:(1) the number of xylem vessels in A. ordosica increased significantly with decreasing precipitation amount, and the density and thickness of xylem vessels increased significantly (P<0.05). A longer precipitation interval would significantly increase the number of xylem vessels, thickness of the xylem vessel'' walls and mean diameter of xylem vessels (P<0.05). The interaction effect of precipitation and precipitation interval on xylem anatomical characteristics of A. ordosica was not significant. (2) The decreased precipitation amount and extended precipitation interval weakened the sensitivity of potential hydraulic conductance in response to xylem vessels'' diameter in A. ordosica. (3) A. ordosica could balance the safety and efficiency of water transport strategy by adjusting xylem vessels characteristics in response to the decreased precipitation amount and extended precipitation interval. This study indicated that by changing xylem anatomical parameters is an important strategy for A. ordosica to adapt to precipitation changes. Both precipitation amount and precipitation interval had effects on hydraulic characteristics of desert plants.