干旱区荒漠景观的植被自然更新机制初探

根据实地调在和参阅资料．依山前洪积扇、河流沿岸阶地、沙丘及丘间低地、戈壁、盐沼的景观斑块，初步探讨干旱区植被的自然更新机制。干旱区的高温干燥、温差强烈、风蚀沙埋已成为植物繁衍后代的动力；萌蘖、劈裂、地下茎萌生等多种繁殖方式．使荒漠植物在严酷的条件下实现自然更新，形成以母株为中心的母系居群。地貌形态和种子传播动力决定了群落外形。在干旱区，以种子繁殖的植物之种子成熟期与年内的丰水期相吻合，有利于植被更新．只有在连续2年降水较大时（超过多年平均降水量），沙丘和丘间地，戈壁植被的自然更新才可能发生；河流沿岸植被的自然更新受地下水影响最明显；湖盆盐碱地植被带有水生植被的痕迹，自然更新相对较难；景观斑块镶嵌分布．形成微环境均异的廊道．有利于植被的自然更新。

Preliminary Study of the Mechanisms of Natural Vegetation Regeneration in Arid Desert Regions

In terms of such landscape patches as piedmont proluvial fan,terrace land by river,sand dune,inter-dune lowland Gobi and salt mash,the mechanisms of natural vegetation regeneration was preliminarily explored in arid desert regions by field survey and data reference.High temperature,aridness,sharp temperature difference,wind erosion and sand burial became the driving force for plants to reproduce in arid regions;diverse reproduction ways such as tiller initiation,splitting,subterraneous stems made desert plants capable of naturally regenerating and thus forming maternal populations around maternal plants.Landforms and seed-dispersal capacity determined population appearances.In arid regions,the seeds of seed plants matured in correspondence with high water period and this was helpful to natural vegetation regeneration;only after heavy rainfall(higher than the average annual rainfall over many years) took places in two consecutive years could natural vegetation regeneration occur on sand dunes,inter-dune land and Gobi.The vegetation regeneration along a river was most remarkably affected by underground water.The vegetations on lake-basin and salt-alkali lands carried hydrophtic vestiges and thus their natural regenerations were relatively difficult.The mosaic distributions of landscape patches formed landscape corridors with different microenvironments and then were conductive to natural vegetation.