内蒙古温带疏林草地生态系统植被—土壤的空间分异特征研究

发布时间：2018-07-24 10:08

【摘要】：以榆树(Ulmus pumila L.)为主要优势种的疏林草地是适应浑善达克沙地植被演替的顶极群落。榆树疏林生态系统具有较高的生境多样性、生物多样性以及结构多样性,在维护区域的生态稳定和生态安全中发挥着不可替代的作用,对控制草地沙化具有重要意义。20世纪后期,在气候变化以及人为活动(农耕、放牧)等因素的影响下,浑善达克沙地榆树疏林遭到破坏,榆树种群的更新受到了极大的限制,整个榆树疏林生态系统的植被盖度、物种多样性也随之降低。榆树疏林生态退化的问题已经影响到了整个区域的生态格局和经济安全。因此,亟需对浑善达克沙地榆树疏林生态系统的空间分布及其影响因素开展相关研究,并以此为浑善达克沙地榆树疏林的保护和恢复工作提供理论支持。本研究以浑善达克沙地榆树疏林为研究对象,通过研究天然状态下榆树疏林的空间分布特征,探讨空间格局的形成原因,分析潜在生态过程以及干扰因子。主要结论如下:(1)榆树种群的年龄结构呈现2个峰值,存在严重断层问题,属于衰退型种群。在东部区域,以第Ⅰ龄级(DBH5 cm)、第Ⅲ龄级(10 cm≤DBH15 cm)和第Ⅳ龄级(15 cm≤DBH20 cm)的榆树较多;在北部、南部和西部区域,第Ⅰ龄级(DBH5cm)、第Ⅴ龄级(20 cm≤DBH25 cm)和第Ⅵ龄级(25 cm≤DBH30 cm)的榆树数量较多。相对于东部区域,北部、南部和西部区域的种群衰退问题更加严重。榆树种群呈现前期锐减、中期稳定、后期衰退的动态特征。榆树种群更新的关键时期处于第Ⅱ龄级(5 cm≤DBH10 cm),在避免对该龄级干扰的基础上加强保护是促进榆树种群良性发展的关键。(2)榆树疏林中主要木本植物(榆树、耧斗叶绣线菊(Spiraea aquilegifolia Pall.)和小叶锦鸡儿(Caragana microphylla Lam.))在小尺度上呈现出显著的聚集分布特征,相对于乔木,灌木具有更大的聚集尺度。种子扩散限制、萌蘖繁殖以及生境异质性可能是影响木本植物空间分布特征的主要作用因子。不同龄级的榆树之间在小尺度上呈现出显著相互促进的作用关系,成年榆树与榆树幼苗呈现“庇护与被庇护”的种内关系。榆树分别与耧斗叶绣线菊和小叶锦鸡儿在所有尺度上(0-50 m)呈现出相互独立的种间关系。榆树与2种灌木各自占据不同的空间位置,未产生直接的种间竞争。(3)榆树的种群密度在东部区域最高,在南部区域最低,北部和西部区域居中。这与该区域内的年均温度呈现出一致的空间分布规律,温度可能是影响榆树种群空间分布的重要环境因子。榆树的种群密度分别与胸径、树高、冠幅呈现相反的空间分布规律,表明榆树种群存在“自疏”现象,随着榆树个体的生长,种群密度逐渐降低。榆树种群的密度和灌木群落的密度之间呈现出显著的负相关关系,表明榆树种群与灌木群落呈现相反的空间分布格局。草本群落与土壤理化性质的空间分布具有较好的一致性,土壤理化性质可能是影响草本群落空间分布的主要作用因子。(4)沙丘对榆树疏林植被和土壤理化性质的空间分布具有显著的影响,不同微地形间的乔木层、灌木层、草本层植被各指标具有显著性差异,背风坡的植被最为丰富,迎风坡最为稀疏。土壤理化性质各指标从丘间地、背风坡、坡顶到迎风坡依次呈现逐渐递减的梯度变化。丘间地的水分状况、土壤结构和养分状况最好,迎风坡最差。(5)放牧是导致林分结构退化的重要干扰因子,随着放牧强度的增加,木本植物的数量逐渐降低。放牧活动对榆树种群空间格局的影响主要体现在对幼树和幼苗的破坏方面,放牧活动降低了榆树种群的空间聚集尺度,加速了“自疏”过程。长时间过度放牧后,放牧压力的降低可能是造成灌木入侵的重要影响因素。(6)榆树显著影响到了冠下草本群落和土壤理化性质的空间分布。榆树疏林中榆树与草本植物之间呈现良好的共生关系。榆树可能通过调节土壤水分的再分配过程和冠下的光照环境对草本植物的生长和土壤理化性质的改善起到促进作用。以榆树孤立木为中心的区域存在明显的沃岛效应。在目前气候条件下,灌木的存在虽未对榆树的生长造成直接影响,但研究发现随着气候干旱的加重,榆树的数量可能会持续减少,灌木(如耐旱植物小叶锦鸡儿)的数量则可能会持续增加。若不采取有效的保护措施,以榆树为主导的疏林草地可能将逐步退化为以灌丛为主导的疏林草地类型。建议通过调控放牧强度、建立自然保护区等措施恢复整个榆树疏林生态系统的活力。
[Abstract]:The sparse forest grassland with Ulmus pumila L. as the main dominant species is the top community adapted to the vegetation succession in Hun Sandan sandy land. The elm forest ecosystem has high habitat diversity, biodiversity and structural diversity, and plays an irreplaceable role in maintaining the ecological stability and ecological security of the region. The land desertification is of great significance in the late.20 century. Under the influence of climate change and human activities (farming, grazing), the elm trees in Hun DAQ sandy land have been destroyed, the population of elm trees has been greatly restricted. The vegetation coverage and species diversity of the elm tree sparse forest ecosystem are also reduced. Elm tree sparse forest ecology is also reduced. The problem of degradation has affected the ecological pattern and economic security of the whole region. Therefore, it is urgent to carry out a study on the spatial distribution of the elm tree and its influencing factors in Hun Sandan sandy land and provide theoretical support for the protection and recovery of elm trees in Hun DAQ sandy land. By studying the spatial distribution characteristics of elm trees in natural elm trees, the reasons for the formation of the spatial pattern, the potential ecological processes and the interference factors are discussed. The main conclusions are as follows: (1) the age structure of the elm population presents 2 peaks, and there is a serious fault, which belongs to the decline population. In the eastern region, The elm trees of the first age class (DBH5 cm), the third age class (10 cm < DBH15 cm) and the fourth age class (15 cm < DBH20 cm) are more; in the north, the southern and western regions, the first instar (DBH5cm), the 5th instar (20 cm < < DBH25 cm) and the sixth instar of the elm are more. The population decline is more serious. The population of Ulmus elm has the dynamic characteristics of sharp decline, mid term stability and later decline. The key period of the elm population regeneration is stage II (5 cm < DBH10 cm). The key to promote the development of elm population is the key to promote the development of elm population. (2) the main woody plants in elm tree sparse forest. Elm, columbine (Spiraea aquilegifolia Pall.) and Caragana microphylla (Caragana microphylla Lam.) showed significant aggregation characteristics on small scales, and shrubs had larger aggregation scales relative to trees. Seed diffusion restriction, tillering reproduction and habitat heterogeneity may affect the spatial distribution of woody plants. The main function factor of the sign is that the elm trees of different ages show a significant mutual promotion on the small scale, and the adult elm and elm seedlings present the intraspecific relationship of "asylum and sheltered". The elm have an independent interspecific relationship with the Columbine and the Caragana microphylum on all scales (0-50 m) respectively. The elm and 2 shrubs occupy different spatial positions and do not produce direct interspecific competition. (3) the population density of elm is the highest in the eastern region, the lowest in the southern region and the middle in the northern and western regions. This has the same spatial distribution as the annual average temperature in the region, and the temperature may affect the spatial distribution of the elm population. Important environmental factors. The population density of elm tree has the opposite spatial distribution with the breast diameter, the tree height and the crown, indicating that the elm population has a "self sparse" phenomenon. With the growth of the elm individual, the population density gradually decreases. The density of the elm population and the density of the shrub community shows a significant negative correlation, indicating the elm species. The spatial distribution patterns of the herd and the shrub communities were in the opposite direction. The herbaceous community and the spatial distribution of soil physical and chemical properties were in good agreement. The physical and chemical properties of the soil may be the main factors affecting the spatial distribution of the herbaceous community. (4) the sand dunes have significant influence on the spatial distribution of the vegetation and soil physical and chemical properties of elm trees. There are significant differences in the indexes of the tree layer, shrub layer and herbaceous layer among the micro terrain. The vegetation of the leeward slope is the most abundant and the windward slope is the most sparse. The soil physical and chemical properties of each index are gradually decreasing gradually from the mound, the leeward slope, the top to the upwind slope. The water status of the hills, the soil structure and the nutrient status are the most. Well, the upwind slope is the worst. (5) grazing is an important disturbance factor that leads to the degradation of the stand structure. With the increase of grazing intensity, the number of woody plants gradually decreases. The effect of grazing activities on the spatial pattern of elm population is mainly in the destruction of young trees and seedlings, and the grazing activities reduce the spatial aggregation scale of the elm population and accelerate the grazing activities. "Self thinning" process. After long overgrazing, the reduction of grazing pressure may be an important factor in the invasion of shrubs. (6) the elm trees significantly affect the spatial distribution of the soil and soil physical and chemical properties under the crown. Elm trees and herbs have a good symbiotic relationship. Elm may adjust the soil by adjusting the soil. In the process of water redistribution, the light environment under Wacom can promote the growth of herbaceous plants and the improvement of soil physical and chemical properties. There is an obvious fertile island effect in the area centered on the isolated elm tree. Under the present climate conditions, the existence of shrubs has not made a direct impact on the growth of elm trees, but the study found that the climate is dry with the climate. The number of elm trees may continue to decrease, and the number of shrubs (such as drought resistant Caragana Caragana) may continue to increase. If no effective protection measures are taken, the elm dominated sparse forest grassland may gradually degenerate into a shrub based forest land type. It is suggested that the natural conservation should be established by regulating grazing intensity. Protective measures and other measures to restore the vitality of the whole elm sparse forest ecosystem.
【学位授予单位】：中国林业科学研究院
【学位级别】：博士
【学位授予年份】：2017
【分类号】：S718.5

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