Abstract:

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 models, we explored the effects of positive interactions on population dynamics and community structures. We reviewed 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 environment 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 importance 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-plant interactions. 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 populations, communities and ecosystems, and conducting research in the context of global warming.

Key words: biodiversity, biomass-density relationship, facilitation, grid-based model, plant community, spatial pattern, stress gradient, zone-of-influence model