Biotic interactions and plant colonisation in the high Arctic

生物相互作用既有积极的(如互惠、促进)，也有消极的(如竞争、食草)，是自然群落的主要结构力量。然而，积极互动的作用仍然需要在这些模型中更好地定义和整合。在快速变化的环境中，物种对变化的反应不仅取决于它们特定的适应能力，还取决于所涉及的生物相互作用，这些相互作用可以促进或阻止植物的生长和建立。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会增加。在北极，非生物限制强烈地影响着植物群落的结构，人们普遍认为便利化可能发挥重要作用，特别是在植物建立过程中。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尚未开发的机会，来测试关于在紧张的非生物条件下，正向生物相互作用在构建植物群落中的相对重要性的预测。他说，我的长期目标是为解释植被变化动态的一般生态学理论的发展做出贡献。我将重点放在北极高植被作为一个模型系统，在这个系统中，生物相互作用放缓，环境约束比低纬度地区更明显。我之前的工作表明，便利化促进了北极高地垫状植物和生物土壤结皮的建立。这两个护士-门徒系统促进了不同的物种(草本和灌木)，因此可以不同程度地改变群落结构。我的计划建议启动独特的大规模种子添加实验，用生物去除土壤结皮来测试：1)种子短缺和安全地点限制的相对重要性；2)在高北极两个不同的护士-门徒系统中，竞争和促进植物定居之间的平衡。首先解决这一系统中的这些理论问题，这项工作也将对理解、保护和未来管理加拿大最北端的生物群做出重大贡献。

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.