人为干扰对乌海市四合木小灌木景观的影响

以乌海市四合木(Tetraena mongolica Maxim)为研究对象,利用2009年Quickbird高分辨率影像,结合四合木群落野外调查数据,对乌海市四合木分布区在不同人为干扰强度下的景观格局和群落进行研究。结果表明:人为干扰越强烈,四合木生境破碎化程度越严重。在植株生理年龄相近,生境相同时,四合木的高度、冠幅以及重要值随人为干扰加剧,变化趋势明显。受人为干扰程度越强地区,其物种丰富度指数越小,生物多样性越低。干扰强度发生变化时,Pielou均匀度指数均在0.77—0.90间。

The impact of anthropogenic disturbance on landscape of Tetraena mongolica shrub in the Wuhai City

Tetraena mongolica Maxim.belongs to a monotypic genus in the Zygophyllaceae and is a super xerophyte and a relic sub-shrub of the Tethys.This species is endemic to a very limited area of West Erods region in the western part of the Ordos Plateau in China.The limited distribution of this sub-shrub makes it an important conservation target.It is ranked as a second-class national endangered plant species as defined by China''s Red Book(endangered species list)and has been considered unique from both a plant taxonomical and regional systematics points of view.Also,from a practical stand point, it plays an important role as a windbreaker and stabilizer of sand and contributes to soil conservation and the regulation of hydrological regimes.Populations of T.mongolica serve as an important element in ecosystem functioning and buffer local ecosystems against desertification.Deterioration of the environment and anthropogenic disturbance in recent years have resulted in a high degree of landscape fragmentation and habitat loss in the area.As a result,population size and density of T.mongolica have been decreasing dramatically.T.mongolica has become severely endangered.Anthropogenic disturbance caused by the industrial development and rapid urbanization were direct reasons for the T.mongolica population area reduction and landscape pattern change. So research on the anthropogenic disturbance of this species has attracted attention.Landscape is a heterogeneous area composed of many ecosystems. The different process on landscape scale has decisive effects on the formation of landscape pattern. Correspondingly, the pattern that has already formed controls the basic processes of landscape. The relationship between anthropogenic disturbance, pattern and process has become a research focus which landscape ecology is interested in. A comparative analysis in anthropogenic disturbance of T.mongolica is ecologically important and will help document the threats to T.mongolica and offer a scientific basis for establishing protective measures for this species.The present study explored the association of T.mongolica distribution with anthropogenic disturbance in Wuhai city. With the support of the geographical information system technology and the analysis software of landscape pattern, quick bird high-resolution images and community field survey data of T.mongolica were used to investigate the distribution of T.mongolica. The Result indicates: Be closer to urban area or anthropogenic disturbance from mining, the T. mongolica landscape gets involved in more terrible situation by the increase of anthropogenic disturbance. Moreover, under the influence of anthropogenic disturbance, the canopy size of T. mongolica will decrease and the height of T.mongolica tends to decrease as well. In case of located in those regions where may generate significant strong anthropogenic disturbance, the species richness index and biodiversity are lower than which from other areas.When the anthropogenic disturbance changes, Pielou evenness index typically stays between 0.77 and 0.90. It is indicated that the industrial development and rapid urban expansion caused by irrational land use were direct reasons for the T.mongolica population area reduction and landscape pattern change of the research region.