Biotic interactions and plant colonisation in the high Arctic

生物相互作用的积极（如互惠，促进）和消极（如竞争，草食动物）是主要的结构力量在自然界。然而，积极互动的作用仍需更好地界定并纳入这些模式。在一个迅速变化的环境中，物种对变化的反应不仅取决于其特定的适应性，而且还取决于所涉及的生物相互作用，这些生物相互作用可以促进或抑制植物的生长和建立。目前的共识是，随着环境压力的增加，积极的生物相互作用的相对重要性应该增加。在北极，非生物限制强烈影响植物群落结构，它通常被暗示，易化可能发挥重要作用，特别是在植物建立。然而，在这个系统中，生物相互作用很少被量化。北极提供了一个难得的未开发的机会，以测试预测的相对重要性，积极的生物相互作用，在构建植物群落在压力非生物条件下。 我的长期目标是为解释植被变化动态的一般生态理论的发展做出贡献。我专注于高北极植被作为一个模型系统中，生物的相互作用是缓慢的，环境的限制比在低纬度更明显。我以前的工作表明，促进建立垫植物和生物土壤结皮在高北极。 这两个保育系统促进不同的物种（草本植物与灌木），因此可以在不同程度上改变群落结构。我的计划建议启动独特的大规模种子添加实验，生物土壤结壳去除测试：1）种子短缺和安全场地限制的相对重要性; 2）在高北极的两个对比的护士保护系统中，植物殖民化的竞争和促进之间的平衡。首先要解决这个系统中的这些理论问题，这项工作也将是加拿大最北端的生物群落的理解，保护和未来管理的重大贡献。

Biotic interactions both positive (e.g. mutualism, facilitation) and negative (e.g. competition, herbivory) are major structuring forces in natural communities. However, the role of positive interactions still needs to be better defined and integrated in these models. In a rapidly changing environment, species response to change will depend not only on their specific adaptations but also on the biotic interactions involved that can promote or prohibit plant growth and establishment. The present consensus is that with increasing environmental stress the relative importance of positive biotic interactions should increase. In the Arctic, abiotic constraints strongly affect plant community structure and it is generally implied that facilitation may play an important role, especially in plant establishment. Yet, biotic interactions have been rarely quantified in this system. The Arctic offers a rare untapped opportunity to test predictions on the relative importance of positive biotic interactions in structuring plant communities under stressful abiotic conditions.     My long-term objective is to contribute to the development of general ecological theory explaining the dynamics of vegetation change. I focus on high arctic vegetation as a model system in which biological interactions are slowed and environmental constraints more pronounced than at lower latitudes. My previous work revealed that facilitation promotes establishment in cushion plants and biological soil crusts in the High Arctic.  These two nurse-protégé systems promote different species (herbs vs shrubs) and thus can alter to various degree the community structure. My program proposes to initiate unique large scale seed addition experiments with biological soil crust removal to test: 1) the relative importance of seed shortage and safe site limitation; and 2) the balance between competition and facilitation in plant colonisation in two contrasting nurse-protégé systems of the High Arctic. First to address such theoretical questions in this system, this work will also be a significant contribution to the understanding, conservation and future management of Canada's northernmost biome.