干旱区荒漠景观植被自然更新机制初探

根据实地调查和参阅资料，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，探讨干旱区荒漠植被的自然更新机制。干旱区的高温干燥、温差强烈、风蚀沙埋已变为植物繁衍后代的动力；萌孽、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，繁殖植物的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2a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有可能发生。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，形成微环境均一的廊道，有利于植被的自然更新。

Preliminary Study on the Mechanism of Natural Regeneration of Vegetation in Desert Landscapes in Arid Areas

The area of arid regions in China occupies 52.5%, where it belongs to the typical continental climate, the precipitation is less, strong winds occur frequently, and the aeolian landforms are dominant. Desert vegetation is the main vegetation type in arid regions, and its regeneration relate closely to the sustainable maintenance and development of all the ecosystems. In this paper, the mechanism of natural regeneration of vegetation in an arid area is preliminarily studied based on the field investigation and the references about the landscape patches of the fore-mountain alluvial-diluvia fans, terraces, dunes, interdune lowlands, Gobi deserts, salty swamps, etc. In the arid areas, the high temperature, aridity, high diurnal-nocturnal temperature difference, wind erosion and sand burying are the driving forces for the plant reproduction; under the severe conditions in arid areas, desert plants can naturally regenerate by many reproduction ways, such as the germination, tillering and rhizomatous germination, thus, the maternal vegetation communities generate by taking the maternal plants as the cores. Landforms and driving forces of seed spread affect the shapes of vegetation communities. In arid areas, the mature stage of plant seeds accords with rainy season, which is advantageous for the regeneration of natural vegetation; only relying on two successive rainy years (the annual precipitation is higher than the average) can the natural regeneration of vegetation growing on dunes, interdune lands and Gobi deserts occur. The regeneration of the riparian natural vegetation affects significantly groundwater depth. In arid areas, the vegetation growing around lakes and in saline or alkaline lands is hydrophyte-like, so its natural regeneration is relatively difficult. The corridors with different microscopic environments caused by the inlaid distribution of landscape patches are advantageous for the natural regeneration of vegetation.