毛乌素沙地油松的水分关系参数随不同土壤基质的变化

CHANGES OF MAIN WATER RELATIONS PARAMETERS IN PINUS TABULAEFORMIS TREES IN RELATION TO DIFFERENT SOIL SUBSTRATE FEATURES IN THE MU US SANDLAND

毛乌素沙地作为一个生态过渡带对环境波动及人为干扰十分敏感 ,植树造林对于防治沙漠化具有重要意义。为了有效地防风固沙 ,近些年在这里成功地营建了油松林带。但是 ,由于缺水 ,油松的生长经常受到严重制约。而且 ,这种制约由于土壤基质的差异性而得到加剧 ,因为土壤基质的差异会导致水分可利用性的不同。因此 ,很有必要研究生长于不同基质条件下的油松的生理特征。本文选取生长在典型沙丘及梁地 (白垩纪及侏罗纪砂岩 )上的油松 ,研究了其蒸腾作用 ,叶水势及抗旱性特征。主要结果为 :1 )在春季少雨季节 ,梁地油松比沙丘油松经历着更严重的干旱 ,因此 ,在春季的林带管理中应特别注意梁地油松的树情 ,并根据植物水分状况适当灌水。 2 )由于沙丘土壤的保水性差 ,即使在夏秋雨季也不能有效保持水分 ,因此 ,沙丘油松林带应注意密度控制。 3)本研究所测得的油松叶子的初始质壁分离点的渗透势可作为油松在不同土壤条件和不同季节受干旱胁迫伤害的参考临界值 ,也可以指示油松对灌水的需求。

Shrub and tree planting plays an important role in combating desertification in Chinas Mu Us Sandland,an ecotone sensitive to both the environmental fluctuations and anthropogenic disturbances.Recent years has witnessed the success of establishing Pinus tabulaeformis tree belt in purpose of wind breaking and sand fixing in this area.However,the growth of the Pinus trees is prevailingly constrained by shortage of water.This restriction can be furthered by the persistence of varied substrate conditions that lead to the differences in water availability to plant.As a result,its urgently needed to analyze the physiological performance of this plant growing at the specific soil substrates in this area.This paper studied the water relations,including transpiration,leaf water potential and drought resistance,of the Pinus trees growing at both the typical dune and hard ridge (Cretaceous and Jurassic rocks)substrates.The main results obtained are in the following.(1)In Spring time,the Pinus trees growing at the hard ridge experienced more serious drought than their dune counterparts.This implies that much care is needed for the hard ridge grown rtees in Spring time;(2)The density of the Pinus tree belt at the dune site should be paid special attention to because soil water holding capacity was poorer at this substrate;(3)Osmotic potential at initial plasmolysis obtained from the Pressure Volume curves can be regarded as the threshold points at which leaf tissue begin to be injured by drought stress,and hence can be an indicator for requirement of watering.