毛乌素沙地过渡地带土壤水分特征及其植物利用

毛乌素沙地过渡地带沙地生态系统土壤湿度状况随着地貌部位不同而变化。沙丘迎风坡基质流动、背风坡沙埋沙压和丘间低地潜水埋深等控制着沙地土壤水分分布规律 (土壤湿度模式 )和沙地植物利用土壤水分的特点 (沙生植物分布模式 )。沙生植物的水分利用的机制主要体现在如下两个方面 :地上部分的生理生态过程和生物量 :地下部分根系分布及其土壤水环境容量。在沙丘从流动变为固定的过程中 ,固沙林形成后的土壤水分动态和灌木林群落实际蒸腾蒸发规律的关系反映不同植被覆盖、不同密度、不同年份和不同季节水分平衡状况 ,藉以确定合理的土壤水分消耗模式 ,维持固沙林群落的稳定和良性演替。为了提高沙生植物水分利用效率 ,一是从沙生植物本身的生理、生态、遗传特性进行分析研究 ,筛选出耐旱和抗水分胁迫强的品种。乡土灌木树种能有效地使个体和群落恢复 ,但也应注重引种。另一方面则是利用各种抗旱保水新材料最大限度地保存和利用固沙林地的水分以满足植物特别是在春旱期间根系的恢复与生长需要 ,即以吸水剂、保水剂、水分表面活化剂、菌根剂和土壤生物制剂 (例如细菌肥料 )等为原材料的新型抗旱造林技术 ;三是依据沙地水环境容量 ,合理确定各种灌木林的造林密度及其与沙丘发育阶段相应的种群配置格式。

Soil Moisture Regimen and Application for Plants in Maowusu Transition Zone From Sand Land to Desert

Soil moisture regimen changes with different localities of topography in Maowuse transition zone from sandy land to desert.Soil moisture distribution in sandy land(soil moisture models)and the characteristics of soil water used by sand plants(sand plant distribution models) depend on the conditions such as dune drift on slope facing the wind,dune sand on slope out of the wind and groundwater table within lowlands among dunes.The mechanism of soil water used for sand plants could be demonstrated by the following two aspects:the physiological and ecological processes and biomass of ground parts of sand plants,distribution of root system of sand plants and soil water environmental capacity.In the development of mobile dunes changing into fixation ones,the relationships between soil moisture dynamics after the formation of shrub communities on stabilizing mobile sand and actual evapotranspiration of shrub communities would show the regimens of soil water balance of different vegetative cover,different densities of shrub communities,different years and seasons.Cobinated with which,the application of soil moisture models could be helpful to establish and keep a sustainable and better successed community.In order to improve water utilization rate of sand plants,the following 3 aspects should be taken (1)Selecting the drought resistant species by the analysis of the characteristics of physiology,ecology and heredity of sand plants.Native species will be available for rehabilitation of individuals or communities,however,it is important to pay more attention to importing species;(2)New materials of anti-drought and soil water conserved should be used for the establishment of shrub communities of stabilizing mobile sand,especially for recover and growth of root system during the period of spring drought,such as gel-forming cross-linked polyacrylamide,water save surfactant,ctomycorrhizal fungus and other soil microbe preparations and (3) Densities of shrub communities of stabilizing mobile sand and disposition of different communities in responses to phrases of dune development should be in accordance with soil water environmental capacity. \ \