摘要
沙漠 -绿洲过渡带地区植被的可持续性在防止绿洲沙漠化的过程中非常重要。对过渡带主要植物种骆驼刺 (Alhagisparsifolia Shap)、多枝柽柳 (Tamarix ramosissima L ebed.)、胡杨 (Populus euphratica Oliv.)和头状沙拐枣 (Calligonum caput-medusae Schrenk.)水分关系的研究表明 :4种植物的水分恢复状况良好 ,清晨水势一直较高 ,水分亏缺并不严重。渗透势和正午水势的降低幅度不大 ,变化比较平稳 ,更像是一种生长过程中的结果 ,植物的水分胁迫状况并不明显。 4种植物的水势和渗透势都高于典型的荒漠植物 ,属于中生植物的范围。水分参数的变化显示在同样的环境节律下 ,四种植物在水分生理的变化特征上有一致性。一直很高的 RWCp 值表明植物不能适应剧烈的水分损失和较低的水分含量 ,植物需要稳定充足的水分供应来适应塔克拉玛干极端气候条件下的生长环境。植物对环境胁迫也有各自不同的生理适应特点 ,胡杨的ΔΠ值大 ,能忍受较多的水分损失维持气孔的开放 ;骆驼刺的Ψp 值最高 ,水分亏缺的平衡与恢复效果明显 ;C4 植物头状沙拐枣能维持较高的水势和渗透势 ,而盐土植物多枝柽柳能忍受水势的很大降低。夏季一次性灌溉对骆驼刺、多枝柽柳和胡杨水分状况的改善基本没有影响 ,对头状沙拐枣有一定的帮助。植物?
Qira (Cele) oasis is located at the southern fringe of the Taklimakan Desert, the most arid region in northwest of China, where the mean annual precipitation is less than 40 mm and the potential evaporation is about 2600 mm. The perennials Alhagi sparsifolia Shap., Tamarix ramosissima Lebed. and Populus euphratica Oliv. are dominant and important indigenous species in the transition zone between open desert and the Qira oasis. Calligonum caput-medusae Schrenk., which is native to Xinjiang, but not to the region of Qira, has been planted. Besides sheltering the oases against wind blown sand, these species are used for grazing, as livestock forage, as material for house and fence construction, and as fuel. In view of the strong population increase in Qira, the restoration and extension of the vegetation formed by these species is of high ecological and economical importance. Generally, water is the limiting factor that restricts vegetation restoration and regeneration in desert areas. Investigations into the water relations of plants can provide valuable information on the capability of plants to cope with the harsh conditions. Moreover, they can be helpful in planning the most effective use of the limited water resources for vegetation regeneration in the transition zone of the oases. Therefore, the intentions of our investigation were as follows: (1) to assess the occurrence of drought stress in the above named species during the growing season; (2) to assess the significance of physiological and morphological features as adaptations to the extreme environment; 3) to investigate the effect of a short irrigation in summer, performed in order to simulate a natural flood, on water relations of the species. In order to achieve these goals, water-relation parameters of twigs were derived from pressure-volume curves (pV curves) that were established at four-weekly intervals from April to October by applying the pressure chamber method. In addition, daily courses of twig water potentials, including predawn potentials, were measured using pressure chambers, too. The effect of flooding on the soil water content was monitored using Time Domain Reflectometry (TDR) with sensors in five different soil depths. An automatic weather station was installed both at the Alhagi and at the Tamarix site, and climatic variables were continuously recorded.The results showed that only moderate water deficits occurred in A. sparsifolia, T. ramosissima, P. euphratica and C. caput-medusae. All species were able to balance the deficits that developed during a day until the next morning, and maintained nearly constant and rather high predawn water potentials during the growing season. Except for T. ramosissima at one date, the water and osmotic potentials decreased only moderately during the growing season, and this seemed to be an endogenous process that was not caused by drought stress. Generally, the water and osmotic potentials of the investigated species were higher than those of typical desert plants and were within the range of mesophytes. Under similar environmental conditions, the investigated plant water relation parameters of the species varied in a similar way during the growing season. Incipient plasmolysis occurred in all species at high relative water contents, indicating that these plants are not adapted to strong water loss and low water contents. Rather, they are depending on a constantly sufficient water supply to cope with the extremely high water pressure deficit and the correspondingly high evaporative demand of the atmosphere at their growing sites. Besides this general characteristic, the individual species show special features: C. caput-medusae, being a C4-plant with extremely reduced leaves, maintains particularly high mean water potentials during daily courses as well as during the growing season; A. sparsifolia is particularly effective in balancing daily water deficits during the night and reaches the highest predawn water potentials; T. ramosissima, being a salt accumulating halophyte, exhibits comparably low water poten
出处
《生态学报》
CAS
CSCD
北大核心
2004年第6期1164-1171,共8页
Acta Ecologica Sinica
基金
中国 -欧盟合作资助项目 ( ERBIC18CT 980 2 75 )
国家重点基础研究发展规划资助项目 ( G19990 43 5 0 5 0 4)
中国科学院西部之光资助项目
中国科学院创新领域前沿资助项目 ( KZCX-XJL Q-0 5 )~~
关键词
水分关系
干旱胁迫
灌溉效果
地下水
塔克拉玛干沙漠
water relations
drought stress
irrigation effect
ground water
Taklimakan Desert
