伊洛河流域草本植物群落物种多样性

Species diversity of herbaceous communities in the Yiluo River Basin

生物多样性沿环境梯度的变化是生物多样性研究的重要内容,环境梯度包含了多种环境因子(海拔高度、水热条件、人类扰动等)的综合。以伊洛河流域草本植物群落为对象,沿河从入黄河口到河源地选取典型样地调查研究伊洛河流域草本植物群落物种多样性及其分布格局。结果表明:物种丰富度和Shannon-Wiener多样性指数沿河均稍呈"S"型曲线变化,不同群落类型中分布格局差别不大,各群落类型中的物种丰富度和多样性均呈现出中游丘陵山地交界区最高,上游河源区次之,下游平原地区最低的趋势;β多样性指数的变化趋势与α多样性较一致,总体上呈现出中游丘陵山地区物种更替速率较快,平原区更替较慢;在流域内上游河源地属于自然植被区,人为干扰较轻,具有较高的物种多样性,物种替代主要受物种的竞争扩散能力和生境条件的制约;在下游平原农业区,人类活动强烈,区域内以人工生态系统为主,物种组成简单,物种替代具有跳跃性的特征,主要受人类活动的制约;在中游从自然生态系统向农业生态系统的过渡区域,人类活动的扰动有一定的强度,导致该区域内自然分布种和伴人种混合生长,具有较高的物种多样性和较快的物种替代速率。总体上伊洛河流域草本植物群落物种多样性分布格局强烈的受到人类活动的影响,物种替代速率较高。

Pattern of biodiversity along environmental gradients is one of the basic issues in the biodiversity studies. The environmental gradients include several factors, such as elevation, water and thermal conditions, anthropogenic impacts, and so on. Especially the altitudinal gradient incorporates multiple resource gradients which vary continuously differently. This study was conducted in the Yiluo river basin, straddling Henan and Shanxi Province （109°43＇-113°10＇E, 33°39＇- 34°54＇N）, ranging from 101 m to 1227 m. The Yiluo River is an important tributary of Yellow River in the south side of the middle reaches. The vegetation in drainage basin ecosystem of Yiluo River has been heavily impacted by human. In this research, we focused on the herb communities in different habitats formed by different disturbance types and intensity alongdifferent environmental gradients in the drainage area of the Yiluo River. A field investigation was conducted in August and September of 2009, to describe the distribution two aspects, alpha diversity and beta diversity, environmental explanation. This study explored patterns and the abundance features of the species in different habitats, from the altitudinal gradient distribution pattern of the herb biodiversity and its the influence of human and natural disturbance on the distribution patterns of species within the drainage area, with purposes of offering a scientific guidance to the restoration of the biodiversity in the herbs communities, the management of the watershed and the evaluation of its ecological environment, so as to promote thesustainable use and harmonious development of the watershed eco-system. Using community ecology techniques, we sampled 134 20 m×20 m plots. Each plot consisted of five 1 m×l m quadrats （the four corners and the center）. We recorded the frequency, density, coverage, height and phenophase of plant species present in the quadrats, as well as ecological conditions of the sampling sites. The results of this study show that： both Patrick richness index and Shannon- Wiener diversity index were slightly S-shaped curve shaped; plant community types did not differ markedly in the distribution pattern of alpha diversity; the species abundance and species diversity were higher in the hilly regions of the river＇s middle reaches, and lower in the plains of the river＇s lower reaches; the beta diversity had a similar distributionpattern to alpha diversity ; species replacement rates were higher in the hilly regions and lower in the plains. The upper reaches were largely covered by natural vegetation; with light anthropogenic disturbance, relatively high species diversity, and stable species replacement rate ; the distribution of a species was mainly constrained by its competitiveness and dispersal ability, as well as habitat conditions. The intensively farmed lower reaches were dominated by agricultural ecosystems; species compositions were simple, while species replacement rates could be abrupt, and species distributions were mainly influenced by human activities. The hilly transition zone of the middle reaches was under moderately intense anthropogenic disturbance, natural and accessory plant species grew together in the mixed communities, with relatively high species diversity and replacement rate. To sum up, the pattern of herbaceous species diversity in the Yiluo river basin was strongly influenced by human activities, with high species replacement rate.