Abstract: The statistical and quantitative analysis of botanical composition,quantitative characteristics,life form,dominance and diversity were carried out on different sized patches in the fragmental Leymus chinensis(Trin.) Tzvel.grassland of Songnen Plain.The results are as follows: The number of the plant species,species richness(Margalef index),species diversity (Shannon-Weiner index),and evenness(Pielou index) varied univocally along with the patch scale from big to small,which supported the Intermediate Disturbance Hypothesis;For the functional group composition in sense of life form,along with the patches from big to small,the percentage of chamaephyte and hemicryptophytes decreased gradually with the biggest value of 40.0% and 6.7% appeared on big patches,the hemicrypto-geophyte and geophyte increased little by little with the medium and small patches had the biggest value at 25.0% simultaneously,while the changing trend of therophyte was decreased at first and then increased with the big patch owning the biggest value at 13.3%.The irregular changes of dominance ratio of a given species and the regular changes of the functional groups revealed that the ecological compensation not only operated among functional groups in a community but also among individual species within a functional group.

Key words: Environment fragmentation, Patch, Plant diversity, Spatial variation, Life form

摘要： 在松嫩平原环境破碎化的羊草(Leymus chinensis (Trin.) Tzvel.)草地,对大、中、小3个羊草斑块的植物组成、数量特征、生活型、优势度及物种多样性进行统计和定量化分析。结果表明:随着斑块由大到小,植物种数、Margalef丰富度指数、Shannon-Wiener多样性指数及Pielou均匀度指数均呈单峰型的变化趋势,有力地支持了中度干扰假说;在植被的生活型功能群组成中,随着斑块由大到小,地上芽及地面芽植物比例逐渐减小,最大值40.0%和6.7%均出现在大斑块上,地面-地下芽植物及地下芽植物比例则逐渐增加,最大值25.0%同时出现在中等斑块及小斑块上,而一年生植物比例呈先减小后增加的变化趋势,最大值13.3%出现在大斑块上。某些单个物种优势度比例的不规则变化和功能群组成的规则变化表明,生态补偿作用不仅存在于植物群落的各个功能群之间,而且存在于同一功能群内部的不同物种之间。

关键词: 环境破碎化, 斑块, 植物多样性, 空间变化, 生活型