中文摘要：

植物间的相互作用对种群动态和群落结构有着重要的影响。大量的野外实验已经揭示了正相互作用（互利）在群落中的普遍存在及其重要性。为了弥补野外实验方法的不足,模型方法被越来越多地应用于正相互作用及其生态学效应的研究中。该文基于个体模型研究,探讨了植物间正相互作用对种群动态和群落结构的影响。介绍了植物间正相互作用的定义和发生机制、植物间相互作用与环境梯度的关系。正相互作用是指发生在相邻的植物个体之间,至少对其中一个个体有益的相互作用。植物通过直接（生境改善或资源富集）或间接（协同防御等）作用使局部环境有利于邻体而发生正相互作用。胁迫梯度假说认为互利的强度或重要性随着环境胁迫度的增加而增加,但是越来越多的经验研究认为胁迫梯度假说需要改进。以网格模型和影响域模型为例,介绍了基于个体的植物间相互作用模型方法。基于个体模型,对近年来国内外正相互作用对种群时间动态（如生物量-密度关系）、空间分布格局和群落结构（如群落生物量-物种丰富度关系）影响的研究进行了总结。指出未来的研究应集中在对正相互作用概念和机制的理解,新的模型,新的种群、群落,甚至生态系统问题,以及在全球变化背景下进行相关的研究。

英文摘要：

Plant-plant interactions play an important role in determining the population dynamics and community structures. Field experiments have highlighted the existence and importance of positive interactions （facilitation） in plant communities. To go beyond the limitations of empirical field studies, mathematical and simulation models have been increasingly used in the facilitation studies. In the present work, based on individual-based simulation mod- els, we explored the effects of positive interactions on population dynamics and community structures. We re- viewed the definitions and mechanisms of positive interactions in plant communities and the changes in plant-plant interactions along environmental gradients. Positive interactions are the relationships between plants that benefit at least one of the participants. Positive interactions occur when one plant makes the local environ- ment more favorable for its neighbor either directly （such as by habitat amelioration or resource enrichment）, or indirectly （such as by associational defense）. The stress gradient hypothesis predicts that the strength or impor- tance of facilitation should increase with the severity of environmental stress. However, a growing number of studies suggested that the stress gradient hypothesis might need further refinement. Using grid-based models and zone-of-influence models as examples, we reviewed individual-based approaches for modeling plant-plantinteractions. Furthermore, we focused on the applications of these individual-based simulation models in this field, and summarized the studies on the effects of positive interactions among plants on population dynamics （e.g. biomass-density relationship）, spatial pattern and community structures （e.g. community biomass-species richness relationship）. We also presented future directions for facilitation research. Further research should focus on deeper understanding of the concepts and mechanisms of positive interactions, new models, new ecological questions of plant popula