作 者 ：徐先英,孙保平,丁国栋,郭树江,柴成武
期 刊 ：生态学报 2008年 28卷 3期 页码：895~905
Keywords:sand-fixing, desert shrub, SHB, sap flow, drought tolerance, weather factor,
摘 要 ：利用澳大利亚Dynamax公司生产的热平衡包裹式树干液流仪（Stem Heat Balance, SHB）和自动气象站对干旱荒漠区3种固沙灌木梭梭、多枝柽柳和唐古特白刺的液流变化及其气象因子进行测定， 研究了3种固沙灌木茎干液流日、季变化规律以及对气象因子的响应。结果表明：(1) 在生长季，不同地茎、不同树种液流启动时间存在差异， 地茎1.70、 3.64cm和5.07cm的梭梭启动时间分别为 5:00~7:00、5:00~7:20和6:00~8:00； 地茎1.57cm和3.03cm的柽柳启动时间5:20~7:20和5:40~7:40；地茎1.59cm白刺启动时间6:00~8:00。梭梭的日变化表现为双峰型，最高峰出现在11:40~13:20；而柽柳和白刺日变化表现为多峰格型,最大峰值分别出现在12:40~13:00和12:00~13:00；3种灌木液流在中午存在“午休”现象，但“午休”不明显。(2) 3种固沙灌木在夜间也保持一定的液流速率，而且地茎越粗夜间液流持续的时间越长，越细持续时间越短，不同地茎灌木在第2天液流启动之前，夜间液流都有一个明显的下降过程， 甚至为0。(3) 3种典型固沙灌木茎干液流季节变化表现为单峰型，梭梭和柽柳茎干液流8月份最高，7月份次之，6月与9月基本一致，而白刺7月份最高，8月次之；在整个生长季，相近地茎3种灌木单位面积液流量为：白刺﹥柽柳﹥梭梭, 梭梭耐旱性较高。(4)气象因子对不同树种茎干液流的影响有一定的差异，茎干液流与气象因子的关系比较复杂。相关分析表明，在整个生长季，空气水汽压差或气温对梭梭起主导作用，而太阳辐射对柽柳和白刺起主导作用。
Abstract:Haloxylon ammodendron, Tamarix ramosissima and Nitraria tangutorum are widely used sand-fixing shrubs in sandy desert areas. They are well adapted to sandy conditions. However, the understanding on the patterns of stem sap flow of the three shrubs is poor. The diurnal and seasonal variations of sap flow were measured with Stem Heat Balance(SHB), and the simultaneous weather factors were observed at a nearby automatic weather station from May to October in 2006. The results showed that the starting time of sap flow was species-specific and varied with stem diameters within a species. The sap flow of H.ammodendron stems with basal diameters of 1.70cm, 3.64cm and 5.07cm started at 5:00-7:00, 5:00-7:20 and 6:00-8:00, respectively. That of T. ramosissima stems with 1.57cm and 3.03cm basal diameters started at 5:20-7:20 and 5:40-7:40, and that of N. tangutorum stems 1.59cm basal diameters started at 6:00-8:00. The diurnal variations of sap flow showed a bi-peaked curve for H. ammodendron, and a multi-peaked curve for T. ramosissima and N. tangutorum. The maximum velocity of sap flow appeared during 11:40-13:20 for H. ammodendron, 12:40-13:00 for T. ramosissima and 12:00-13:00 for N. tangutorum. All of the three species had an ambiguous noon-depression phenomenon of the sap flow curves. There was sap flow occurred at night for the three shrubs, but the duration of the flow at night varied with stem diameters. The larger the stem diameter, the longer the duration of sap flow at night. The sap flow of the three shrubs at night had an obvious decreasing course and approached zero prior to the sap flow started next day. The seasonal variations of sap flow for the three shrubs showed a unimodal pattern, in which the highest value occurred in August for H. ammodendron and T. ramosissima, and in July for N. tangutorum. During the entire growing season, the unit area sap flow intensity for the three shrubs with similar stem diameters ranked as N. tangutorum ﹥T. ramosissima ﹥H. ammodendron from high to low, which implied that the drought tolerance of H. ammodendron was higher than that of N. tangutorum and T. ramosissima. The results showed that vapor pressure deficit or air temperature was the major weather factor affecting sap flow for H. ammodendron, and solar radiation for T. ramosissima and N. tangutorum, which indicated that the weather factors played different roles in affecting sap flow of the three shrubs.
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