【作者】 李岳坦；

【导师】 李小雁；

【作者基本信息】 北京师范大学 ， 自然资源， 2010， 博士

【摘要】 青海湖作为青藏高原的重要组成部分,是维系青藏高原东北部生态安全的重要水体,是国际重要湿地。近几十年来由于气候变化、过度放牧及人类活动的影响,流域内的植被出现了不同程度的退化。河流是青海湖流域重要湿地类型,但河岸植被严重退化影响了河流生态系统健康,进而对流域整体生态环境产生十分不利的影响。因此,对青海湖流域河岸植被群落结构特征及退化机理进行研究,可为流域内河岸植被退化研究提供理论基础,有助于开展河岸植被生态恢复,从而保证青海湖流域社会经济的健康发展。论文以沙柳河为例,在对河岸植被进行样方调查的基础上,研究了沙柳河流域河岸植被的群落组成、生物多样性和生态位等群落结构特征;利用实测的水柏枝林地和草地的微气象数据、棵间土壤蒸发量数据,分析了两种植被类型的能量平衡和蒸散规律,并通过对流域内气候变化特征、沙柳河河川径流量变化、河岸稳定入渗率和饱和导水率等进行分析的基础上,结合实地考察资料,分析和探讨了流域内河岸植被退化的原因,并在此基础上提出了退化河岸植被修复方案,主要研究结论如下:1.在沙柳河河岸植被组成中,草本样地分为芨芨草群落、西伯利亚蓼+盐地凤毛菊群落、珠芽蓼+高山嵩草群落等12种植被类型,灌木样地分为具磷水柏枝群落、金露梅群落和沙棘群落等3种植被类型。草本植物群落的分布与海拔高度和土壤总盐量显著相关,而灌木植物群落的分布与沿河道距入湖口的距离和距河道的垂直距离有关,但是关系不显著。2.沙柳河流域中主要优势灌木种水柏枝和草地在能量平衡和蒸散方面差异显著,水柏枝林地的地下5cm土壤热通量与冠层净辐射变化趋势一致,而草地的地下5cm土壤热通量与冠层净辐射存在1小时的延时,草地和水柏枝林地的显热通量在白天均为负值,而潜热通量在白天均为正值。在生长季,水柏枝林地的蒸散量显著大于草地的蒸散量,二者的日蒸散强度相差0.7mm/d,水柏枝林地月平均蒸散量的大小为148.7~223.6mm,草地月平均蒸散量的大小为146.2~179.3mm,水柏枝林地的蒸散耗水主要依靠河水补给,而草地的蒸散耗水主要依靠雨水补给。3.在沙柳河河岸植被中,绝大多数草本植物群落的多样性指数、均匀度指数和丰富度指数都明显较大,灌木群落的的生物多样性指数、均匀度和丰富度指数都比较小,草本植物群落之间的相似性较小,灌木群落之间的相似性较大。草本植物群落各优势种之间生态位重叠较大,灌木植被群落中,具磷水柏枝、金露梅和沙棘之间的生态位重叠也比较大。4.沙柳河流域河岸植被退化的主要原因是过度放牧,过度放牧导致流域内河岸植被的生物量减小,群落组成发生变化;流域内气候变化和沙柳河河川径流量变化对河岸植被产量和群落演替具有重要影响。此外,流域内工程设施建设和鼠类危害也是河岸植被退化的原因。5.沙柳河流域河岸植被恢复应主要依靠围栏封育、人工种植恢复和确定流域内草场的适宜载畜量等措施。在河岸植被种植过程中,应选择生态位宽度大且适口性为优良的物种,因此沙柳河河岸植被恢复过程中,推荐矮生嵩草、荸荠、垂穗披碱草、大药碱茅、多枝黄芪、华扁穗草、毛穗赖草、青藏苔草、沙生冰草、线叶嵩草、珠芽蓼和紫野大麦物种作为草本植物恢复过程中首选物种,具磷水柏枝和金露梅作为灌木植物恢复过程中的首选物种。要根据物种的自然分布规律来进行种植,珠芽蓼和高山嵩草适合在海拔高度相对较高的地区种植,而垂穗披碱草和草地早熟禾则适合在海拔高度相对较低的区域种植,具磷水柏枝适合生长在3200~3400m的海拔高度范围,而金露梅适合生长在3300~3500m的海拔高度范围。应保持沙柳河的年径流量大于0.75亿m3。加强鼠害治理、进行毒杂草防治以及减少人为因素对植被的破坏也是实现流域内植被恢复的有效手段。更多还原

【Abstract】 Lake Qinghai, the important international wetland, is of great importance for protecting the ecology safety of northeast Qinghai-Tibet plateau. The vegetation degradated during the past decaeds of years due to climate change, overgrazing and human activity. River is the main wetland type of Lake Qinghai basin, and the degradation of riparian vegetation threated not noly the ecosystem health of of river system but also the eco-environment safety of Lake Qinghai basin, so the study on the community structure and degradation mechanism of riparian vegetation in Lake Qinghai basin not only can provide scientific basis for the study of riparian vegetation degradation but also is helpful to vegetation restoration, and so as to make sure that the social economy of the basin has a healthy development.Based on the samples of the riparian vegetation of Lake Qinghai basin, the community structure, biodiversity and niche of riparian vegetation was studied, and also the energy balance and microclimate of riparian vegetation was studied by the data of microclimate and soil evaporation. The cause of vegetation degradation was studied by analyzing the climate change of Lake Qinghai basin, streamflow of Shaliu river, stable infiltration and saturated hydraulic conductivity on the banks of Shaliu river, here are the key conclusions.1. The herbosa raparian vegetation on the banks of Shaliu river was classified into 12 kinds of different groups, and shrubs was classified into 3 kinds of different groups. The distribution of herb communities has a sigificant correlation with altitude and soil salt content, while the fruticetum was not sigificant affected by the distance to Lake Qinghai along Shaliu river and the vertical distance to river.2. The shrub’s changing trend of the 5cm underground soil heat flux is the same as the canopy net radiation, while the grassland has an one hour time lapse compared to shrub, the sensible heat flux of shrub and grassland is negative during the daytime, while the latent heat flux is positive. During the growing season, the daily evapotranspiration of shrub is 0.7mm lager than grassland, and the monthly evapotranspiration of shrubs is 148.7~223.6mm, while the grassland is 146.2~179.3mm, the water consumption of shrub evapotranspiration is supplied by the streamflows of Shaliu river, while the grassland by the precipitation.3. Almost all the herbosa have a great value of diversity index, species richness and species evenness, while the shrubs have a small value of diversity index, species richness and species evenness. The herbosa of the raparian vegetation shows the small similarity index , while the shrubs shows the big similarity index. Almost all the herb dominant species have the great niche overlap, so dose all the shrub dominant species but Salix qinghaiensis Y.L.Chou.4. The vegetation degradation is mainly caused by overgrazing in this area, and overgrazing can cause the decrease of the biomass and the change of community composition. The rise of temperature and the streamflow change of Shaliu river can affected the biomass and degradation of the riparian vegetation, and moreover the vegetation degradation can also affected by construction and grassland rodent.5. Enclosure, planting and optimum stock capacity are the main reparation method in the study area, and during the reparation species with palatability and wide niche breadth can be selected to plant, and the natural distribution law of the species should be followed. The streamflow should be kept more than 0.075 billion m3, and prevent and cure the grassland rodent and poisonous weeds and reduce the damage to riparian by human should also be the effective method.更多还原