Abstract:

Under the background of global climate change, understanding the species diversity characteristics of mountain plant communities and their environmental influencing factors in arid and semi-arid regions is the basis of regional biodiversity conservation. Helan Mountain was located in the transitional zone between temperate grassland and temperate desert in China. Its eastern and western parts are affected by different climates, making it an ideal area for species diversity study in mountain ecosystems. In this paper, five plant formations widely distributed in the eastern and western parts of Helan Mountain were selected, and their species diversity differences and main influencing factors were investigated by typical community structure and environmental factors analysis. The results showed that: 1) the typical plant communities in eastern and western Helan Mountain were different in species number and water ecological type species compositions. The communities in western part were more arid than those in eastern part, leading to higher numbers of plant species in three formations, i.e., Ulmus glaueescens, Populus davidiana, and Picea crassifolia. 2) The species diversity in the eastern part showed a “hump” pattern along elevation gradients, while in the western region, it decreased as elevation increased. There were significant differences in species diversity between the eastern and western parts of some communities such as Ulmus glaueescens. 3) Soil water content, soil available phosphorus contents, and soil bulk density were key factors affecting the total plant species diversity in the eastern and western Helan Mountains. Among them, soil bulk density and altitude were the main factors affecting the diversity of tree layers. Altitude and soil available phosphorus were the main factors for shrub layers, and soil available phosphorus and water content were the main factors for herbaceous layers. Species diversity of typical forest communities in the eastern and western parts of Helan Mountain, were correlated with altitude and soil physicochemical properties. The measurements which could improve soil physicochemical properties, can promote the growth and development of plants in the forest, thereby helping to increase community species diversity. These results are helpful for further understanding structure and function of mountain ecosystems in arid and semi-arid regions, and provide theoretical basis for conservation and restoration of these fragile mountain ecosystems.

Key words: species diversity, formations, elevation, soil factors, mountain ecosystem in the arid and semi-arid regions

摘要：

深入理解干旱与半干旱地区山地植物群落的物种多样性特征及其环境影响因子，是全球气候变化下区域生物多样性保护的基础。贺兰山脉地处中国温带草原与温带荒漠的过渡带，其东、西侧受不同气候影响，各植被类型的物种多样性特征也存在差异。选取贺兰山东、西侧广泛分布的5个森林群落类型，通过群落组成、环境因子调查，分析贺兰山东、西侧典型植物群落物种多样性的差异及主要影响因子。结果表明，1）东、西侧典型植物群落在物种丰富度、水分生态类型构成上均存在较大差异：西侧群落的环境比东侧更干旱，因此水分生态类型构成上旱生植物的占比更高；在灰榆林、山杨林、青海云杉林中，相同取样面积时位于西侧的植物群落的物种丰富度明显高于东侧。2）物种多样性在东侧表现为随海拔升高先升后降，西侧则沿海拔升高而下降。灰榆林、油松林的物种丰富度在东、西侧存在显著差异。3）东、西两侧总体植物多样性空间分布格局与土壤含水量、速效磷、土壤容重的相关性相对较高。其中，土壤容重、海拔与乔木层多样性的相关性较高，海拔、土壤速效磷与灌木层多样性的相关性较高，草本层的多样性则主要受土壤速效磷、含水量的影响。贺兰山东、西侧典型森林群落的物种多样性与海拔、土壤理化特征具有相关性，因此改善土壤理化性质的林地管理措施可能有助于提高群落物种多样性。研究结果有助于深入理解干旱与半干旱山地生态系统的结构与功能，为脆弱山地生态系统的保育与恢复提供理论依据。

关键词: 物种多样性, 群系, 海拔, 土壤因子, 干旱与半干旱地区山地生态系统