【作者】 李海东；

【导师】 佘光辉； 沈渭寿；

【作者基本信息】 南京林业大学 ， 森林经理学， 2012， 博士

【摘要】 以雅鲁藏布江流域风沙化土地为研究对象，运用遥感技术监测风沙化土地现状分布及动态变化，结合气候变化和人类活动，分析流域内风沙化土地动态变化的驱动机制。调查研究几种主要沙生植物群落的物种组成、种群结构、空间分布和空间关联，及其对高寒流动沙地植被恢复的启示作用。通过人工模拟飞播试验研究，筛选和确定高寒流动沙地人工模拟飞播植物种和最佳播种时间，探讨高寒河谷生境胁迫对人工模拟飞播的影响。以期为西藏高原生态安全屏障建设和风沙化土地的植被恢复与重建提供科学依据。结果表明：(1)雅鲁藏布江流域现有风沙化土地273697.54hm~2，以马泉河宽谷风沙化土地面积最大，占流域风沙化土地总面积的50.28%，其它依次为日喀则宽谷(25.52%)、山南宽谷(19.11%)和米林宽谷(5.08%)。1975—2008年雅鲁藏布江流域风沙化土地呈缓慢增长趋势，近34年间共增长了10.5%，年均增长率为764.71hm~2/a。其中，2008年拉萨和日喀则机场周边风沙化土地共有42462.38hm~2和49871.61hm~2。流域内风沙化土地进一步扩展，是高原特殊气候条件下的缓慢的自然沙漠化过程，是由自然与人为因素共同作用、相互激发、相互促进所形成的人为加速与加剧过程。(2)雅鲁藏布江中游近51年来气温倾向率为0.27℃/10a，高于西藏地区平均值。其中，1961—2007年为0.34℃/10a，气温升高速度高于1961—2007年西藏地区平均值0.32℃/10a。1961—1983年气温属于偏低期，以1983年最小，1984—1994年累积距平曲线呈波动状态，气温增加或减少趋势不明显，1995年累积距平曲线呈波动上升趋势，气温开始显著上升，气温进入偏高期。近51年降水量增加趋势不显著。(3)几种沙生植物种群以集群分布为主的空间分布格局的揭示，可以更好的说明其优越的水土保持、防风固沙性能。集群分布阻挡了地表砂粒被水力、风力的侵蚀搬运，流沙在植株根茎部形成丘状聚沙体。幼龄体的集群生长可以抵御沙埋和风蚀等不利自然条件的影响，有利于成活，是种群适应沙地恶劣条件的一种自然策略。(4)北方优良沙生植物种的人工模拟飞播效果优于西藏乡土沙生植物种。籽蒿、花棒、沙拐枣、杨柴和砂生槐高寒河谷流动沙地的适应性较好。籽蒿在第2年便有花序和种子出现，花棒和沙拐枣在第3年开花结实，籽蒿、花棒和沙拐枣均能完成生活史。但籽蒿的再繁殖能力较弱，花棒和沙拐枣的再繁殖能力较强。不同类型沙丘、沙丘部位对人工模拟飞播效果影响较大。降水状况、沙丘地温、土壤水分含量和风沙运动等生境条件，影响着人工模拟飞播植物的种子发芽、出苗和生长情况。选择6月下旬前后作为最佳飞播期，既能满足新播植物种子发芽和出苗对水分的需求，亦能提供相应的生长期，保证新播苗顺利越冬。更多还原

【Abstract】 Based on a large amount of data acquired from both in situ field surveys andfour sets of remote-sensing images from1975,1990,2000and2008, the types,status and spatial distribution of aeolian sandy lands, as well as the dynamics andresponse mechanisms of this land to climate change over the past34years, werestudied in the Yarlung Zangbo River basin. The population structure, spatialdistribution and association of several psammophyte populations were studied usingpoint pattern analysis, the purpose was to provide theoretical foundation forvegetation restoration on sand dunes. The plant species for artificial seeding andbest sowing period was tested and determined by field artificial seeding trial from2008to2011on sand dune in the alpine valley, and the habitat stress factorsinfluenced on seed germination, emergence and plant growth greatly were discussed.The purpose of this study was to provide a scientific basis for ecological securitybarrier construction and vegetation restoration and reconstruction of aeolian sandyland on the Tibetan plateau. The results showed:(1) There was a total of273697.54hm~2of aeolian sandy land in the YarlungZangbo River basin currently. Aeolian sandy lands in the basin were relativelyconcentrated in various wide valleys and exhibited a decreasing trend from theMaquanhe wide valley in the headwater area to the middle and lower reaches of theriver basin. The Maquanhe wide valley contained the largest proportion of aeoliansandy land (50.28%or137622.94hm~2). During the period from1975to2008,aeolian sandy land in the basin exhibited a slow increasing trend, which increased by10.5%over34years. The total area of aeolian sandy land around Lhasa Airport andShigatse Peace Airport in2008was42462.38hm~2and49871.61hm~2respectively.The Aeolian sandy lands in the basin were found to increase further due to theslow natural desertification process under the arid and windy climate conditions ofthis region, and the combined effects of natural and anthropogenic factors, thesefactors stimulate and promote the processes of anthropogenic acceleration andaggravation.(2) The annual temperature presented a significant increasing trend and thechange rate was0.27/10a from1957to2007in the middle reaches of the YarlungZangbo River. It was more significant than the lower altitudes in other parts of Tibet.The warming trend was more obvious in autumn and winter than in summer. There were obvious periodic oscillation of15-20years for the seasonal and annual meantemperature variations. The abrupt climate change point was about in1987, and thetemperature belonged to the lower period before that time, and higher period afterthat time. The minimum precipitation occurs in1980s. Mean annual precipitationfrom2000to2007is roughly equal to that in1990s or1960s. Inter-decadal andannual variations of precipitation are similar in summer and autumn. Annualprecipitation increases from1957to2007, while it is not significant.(3) Artemisia wellbyi, A. younghusbandii and Sophora moorcroftiana are themajor psammophyte populations on the aeolian sandy land in the riparian ecotone ofthe middle reaches of the Yarlung Zangbo River. We selected four representativeplant communities under different habitat conditions in the riparian ecotone,measured the position, height and crown diameter of each individual in a20m×30m plot and studied the population structure, spatial distribution and association ofthese psammophyte populations using point pattern analysis. The objectives were todetermine how spatial scales are related to population patterns and how speciesspatially adapt to semi-arid conditions in the riparian ecotone, as well as to providetheoretical foundation for vegetation restoration on sand dunes in the study area.(4) The field artificial seeding trial results of northern psammophyte species arebetter than that of native psammophyte species. A. sphaerocephala, Hedysarumscoparium, Calligonum mongolicum, H. fruticosum var. mongolicum and S.moorcroftiana exhibits good adaptability to moving sand land in the alpine valley. A.sphaerocephala begans to flower and seed in the second years, H. scoparium and C.mongolicum begans to flower and seed in the third years, and A. sphaerocephala, H.scoparium and C. mongolicum are all able to complete life cycle. However, thereproducibility of A. sphaerocephala is weak, while H. scoparium and C.mongolicum present strong reproducibility.The morphological characteristics and different parts of sand dunes influencedthe trial results of field artificial seeding greatly. The approach of artificialbroadcast sowing to footprints trampled by feet following the contours proves to be agood way to improve the trial results. The habitat conditions of precipitation, soiltemperature of sand dune, soil moisture content and sand movement affected seedgermination, emergence and plant growth in the alpine valley greatly. The bestsowing period is before and after late June, as the habitat conditions are suitable forseed germination and seedling growth, and it could provide enough growing seasonfor plant growth before winter coming.更多还原