中文摘要：

科尔沁沙地退化沙质草场植被丰富度、盖度可很好地拟合为球状模型,都具有明显的空间结构特征.在所研究区域内,盖度变异幅度明显高于丰富度,但在变程范围内植被丰富度空间变异性强,盖度的空间变异性弱、依赖性强.群落特征、物种和各功能群多样性的空间自相关范围在5.00～38.15 m范围内变化,表现出随着距离的增大空间变异性增强的趋势,但超过其变程后半方差函数值基本稳定在一个极限值附近.沙质草场群落中一、二年生草本、灌木、中旱生植物和旱生植物功能群多样性空间变异性较弱,由随机因素引起的异质性所占的比重较大,且主要表现在5 m以下的尺度范围内.优势种一、二年生草本和旱生植物多样性的变化不仅影响到群落多样性的变化,而且对草场群落及其生态系统的稳定和生态功能的发挥具有重要影响.

英文摘要：

The study area （42°41＇N, 120°55＇E, 360 m a. s. 1. ） is located in Naiman Banner in the centralsouthern part of the Horqin Sandland, where it belongs to the moderate semiarid continental monsoon climate, the annual temperature and annual accumulated temperature ≥10℃ are 6.4 ℃ and over 3 000 ℃respectively, the frost-free period is about 150 days, and the annual precipitation and evaporation are 364.6 mm and 1 972.8 turn respectively. Based on a series of field-investigated data and analyzed results in laboratory, in this paper the community characters and functional group composition in a degenerated sandy steppe in Horqin Sandland are researched. Geostatistical theory and methods are used for describing the spatial variability of community characters and functional group diversity in thedy steppe. The results show that the vegetation richness and coverage can be regressed by spherical model, and they have the distinct spatial variability. The spatial variability extent of vegetation coverage is significant higher than that of vegetation richness in the study area. Semi-variogram model and parameters show that the spatial self-correlation extent of the community characters, species diversity and functional group diversity in the sandy steppe varies in a range of 5.00-38.10 m, their spatial variability is increased with the increase of distance, but the semi-variogram values approach to the unchanged ones when the distance exceeds the effective range. However, the spatial variability of diversity of annual and biennial herbaceous plants, shrubs, intermediate xerophytes and xerophytes is low. Moreover, the proportion of spatial variability caused by stochastic factors is high in the total spatial variability. The change of diversity of the dominant annual and biennial herbaceous plants and xerophytes affects not only the community diversity, but also affects significantly the stability and ecological functions of steppe communities and ecosystems.