【作者】 张超；

【导师】 黄清麟；

【作者基本信息】 中国林业科学研究院 ， 森林经理学， 2009， 博士

【摘要】 灌木林是西藏森林资源的重要组成部分,在维护区域生态安全和促进区域经济社会发展中起着重要的和不可替代的作用。长期以来,由于认识不足,重乔木、轻灌木,灌木林在林业生产和科学研究上均是个薄弱环节。本文在综合论述灌木林的种群与群落特征、空间结构与空间分布以及遥感分类技术等研究现状的基础上,以西藏地区国家特别规定的灌木林为研究对象,从种群、群落和景观尺度上开展了对西藏灌木林评价的研究,并探讨了西藏主要类型灌木林的遥感分类技术。(1)分析了西藏灌木林的群落特征;(2)测度了西藏灌木林种群的生态位,研究了各种群在不同环境中的适应能力和种间竞争关系;(3)分析了西藏灌木林在景观中的格局特征、空间自相关性及其尺度效应,研究了西藏主要类型灌木林的空间结构;(4)分析了灌木林空间分布与环境因子的相互关系,研究了西藏主要类型灌木林的空间分布。(5)通过基于空间分布特征的辅助分类和基于光谱特征的再分类过程,研究和探讨了西藏主要类型灌木林的遥感分类技术。(1)对西藏灌木林群落进行了调查,并分析了其群落特征。研究结果表明,西藏灌木林的科属组成以蔷薇科、蝶形花科和杜鹃花科为主;灌木林群落物种组成较为单一,物种丰富度和多样性均较低,优势树种在群落中所占的比例较大,多形成稳定的原生或次生单优群落;群落的盖度多在0.4以上,不同地区、不同类型灌木林的群落盖度差异较大;受高原环境和西藏灌木树种自身生长缓慢的影响,西藏灌木林的树高多分布于0.1m ~ 6.0m范围,地径多分布于1 cm ~ 5 cm范围,部分类型灌木林的树高与地径之间呈现显著的幂函数曲线回归关系。(2)分别测度了海拔、坡向、坡位和坡度四维环境空间中西藏灌木林种群的生态位宽度和生态位重叠指数,研究结果表明,西藏典型灌木林种群在不同生境条件下,其利用环境资源的能力不同,在海拔、坡向、坡位和坡度的不同状态中,灌木林种群各自表现出其适应的梯度和范围,各种群从环境的不同侧面利用生境资源,每个种群在不同的环境因子上均有一定的适应宽度,通过对其定量测度,有利于进行种群间适应能力的对比;经过长期的自然选择,在各环境空间上,灌木种群间的生态位重叠指数均较大,群落内存在较小的种间竞争,已形成稳定的共生关系,通过对其定量测度,有利于进行种群间竞争与共生关系的研究。(3)在景观尺度上,应用景观生态学原理与方法,定量研究了西藏主要类型灌木林的空间结构。研究结果表明,西藏各类型灌木林斑块大小均服从反J型分布,斑块面积越大,斑块数量越少,所占的面积比例越高。总体上,灌木林面积占景观总面积的4.6%,灌木林斑块数占总斑块数的54.8%。各个具体类型的灌木林在斑块大小、斑块形状和景观镶嵌度等方面均具有不同的格局特征,其空间自相关性均表现为正相关。尺度效应在灌木空间结构特征中表现明显,其中斑块面积、景观镶嵌度、斑块形状和景观多样性等景观指数对空间尺度的变化均表现出较强的尺度敏感性。(4)应用多重对应分析方法,研究了包括经度、纬度、海拔、坡向、坡位和坡度六个环境因子对各主要类型灌木林空间分布的影响程度,并进行了影响因子排序等。研究结果表明,由于西藏地形呈现由东南向西北逐渐抬升的隆起,形成特殊的陆地分布格局和大气环流特点,导致从东向西水分梯度和热量梯度产生经向分异,与灌木林类型的耐寒、耐旱特性相对应,产生了不同类型灌木林空间分布的地域差异。总体上看,西藏主要类型灌木林的空间分布均在不同程度上受大尺度(地域)环境因子的影响,主要表现在经纬度和海拔上,其中,受经度影响较大,表现出明显的经度地带性。此外,一些类型(如狼牙刺和沙棘)的空间分布上表现出明显的垂直地带性。在小尺度(小生境)上,去除经度地带性和垂直地带性的影响,各环境因子通常表现为共同(或组合)影响灌木林的分布,如坡位和坡度共同影响锦鸡儿灌木林的空间分布,坡向和坡位共同影响红柳灌木林的分布等情况。(5)西藏灌木林斑块面积较大,且多为纯林,有利于利用遥感手段进行分类识别。采用逐级分层、分类提取的策略,结合基于空间分布特征的辅助分类和基于光谱特征的再分类过程,对试验区内的各类型灌木林进行了分类识别和提取。研究结果表明,基于空间分布特征的辅助分类精度为86.24%,基本上能够满足林业生产的需要,但其分类结果为灌木林类型的组合,未能识别到具体灌木林类型;通过基于光谱特征的过程,得到的最终分类精度为70.64%,对沙棘、红柳能较准确地识别,而对个别类型(如杜鹃和小檗)的识别精度不高。利用该技术流程和影像数据,可将沙棘、红柳等类型较为准确地识别和提取,其它类型可依据具体的精度要求选择识别到类型或类型组合。更多还原

【Abstract】 As an important part of forest in Tibet, shrub plays an irreplaceable role in regional ecological security maintenance and regional economic and social development. However, shrub has been limited both in forestry production and scientific research because of the incorrect understanding and less attention for a long time. In this paper, based on the review of shrub population and community characteristics, spatial structure and distribution of shrub, as well as remote sensing classification techniques, the research was carried out as following by taking the shrub in Tibet which accorded with the special regulation of national as the research object: (ⅰ) the community characteristics of shrub in Tibet were analyzed; (ⅱ) the populations niche of shrub in Tibet were measured, and the adaptability and interspecific competitions of shrub populations were studied; (ⅲ) the spatial structure of shrub types was studied through the landscape pattern analysis, spatial autocorrelation analysis, and spatial scaling effects analysis; (ⅳ) interactional relationship between environmental factors and distribution of shrub was analyzed, and the spatial distribution of shrub types was studied; (ⅴ) the remote sensing classification technique of shrub in Tibet was discussed, including the process of assistant classification based on spatial distribution characteristics and re-classification based on spectral characteristics.The inventory was carried out and the community characteristics were analyzed. The results show that, the main family compositions of shrub in Tibet are Rosaceae, Papilionaceae and Ericaceae. Species composition in shrub communities is single, and species richness and diversity are at low level. Dominant species in the communities occupy a main proportion, and as a result, stable original or secondary communities with single dominant specie are dominated. Mostly, the coverage of the shrub communities is larger than 0.4, and it is remarkable different in districts and shrub types. Being affected by the plateau environment and shrub species ecology characteristic, the tree height distributes between 0.1 m and 6.0 m, and the ground diameter distributes between 1 cm and 5 cm. The power function curves of H-D of some shrub types show prominent relativity.Niche breadth and overlap indexes were measured at the environmental space including altitude, aspect, position and slope. The result shows that the environmental adaptability is different among environmental factors through the measurement of the population niche characteristics from the four-dimensional environment space. The populations show flexible width to different environmental factors, and it makes the habitat resources useable for each species from different aspects. The comparison of environmental adaptability could be carried out by the quantitative measurement of niche breadth. After a long period of natural selection, the stable symbiosis relationships have been set up with less interspecific competition in shrub communities. The comparison of symbiotic relationship could be studied by the quantitative measurement of niche overlap.The spatial structure of shrub in Tibet was quantitative studied based on the principles and methods of landscape ecology. The patch-size distributions of the shrub types are subject to anti-J shape. Generally, the area of shrub occupies 4.6% of the whole landscape, and the patch number accounts for 54.8%. And, the pattern characteristics of typical shrub types are different in patch shape and size, and positive correlation was showed to the spatial autocorrelation. Scale effect is evident between different spatial extent, and it showed strong sensitivity to scale in patch-size, landscape mosaic, patch shape and landscape diversity index.The interactional relationship between environmental factors and distribution of shrub was analyzed by multiple correspondence analyses. The spatial distribution of shrub is mainly affected by the regional factors, including the terrain, precipitation, light condition, etc. The results show that the most important factor that effects the distribution is the longitude, latitude and altitude, which are from the large-scale region which due to the terrain of Tibet that gradually upheaval from southeast to northwest. At the niche level, the distribution of shrub is usually affected by factors’combination, such as slope aspect, position, slope, etc.Because of the large size of shrub patch and pure stand mostly, it is helpful to the remote sensing classification of shrub types. With assistant classification based on the spatial distribution characteristics and re-classification based on the spectral characteristics, the classification results of shrub types were drawn. The accuracy of assistant classification based on the spatial distribution characteristics is 86.24%, which could meet the requirements of forestry production, and the accuracy is 70.64% based on the spectral characteristics classification. Hippophae L. and Tamarix L. can be identify accurately by using of technical processes image data, other shrub types could be classified to types or type groups depend on the precision request.更多还原