Mechanisms of species assembly and coexistence in vegetation under a changing climate: Plant traits, contested resources, and ecosystem services

保护与恢复生态学的一个基本目标是理解自然植被的物种组成、丰富度和生产力在空间和时间上变化的机制。这些问题的答案对于做出与植被对持续气候变化(降水和温度)、大气污染(氮输入)、入侵物种的成功以及由于人口激增的影响而造成的栖息地和物种丧失有关的缓解预测和建议至关重要。未来几十年，人口数量和密度注定会继续增加。面对这一点，我们还需要学习如何预测我们可以从未来生态系统的新兴特性和服务中期待什么，因为它们正在以新的方式被强大、持久和日益增长的人为选择力量塑造。由于大多数自然植被中的寄生植物的繁殖成功通常受到近邻效应的限制，支持上述目标的指导将需要对物种相互作用的选择后果有深刻的理解。因此，这里提出的研究计划-与9名研究生和15名本科生合作-将检验最近的假设，即影响将后代留在拥挤的植被中(竞争能力)的关键植物性状，以及安大略省东部白尾鹿种群持续激增对觅食的严重影响-并将研究水和养分作为中生生境土壤资源竞争的关键对象的作用，预计随着气候变化的展开，中生生境的土壤资源竞争将变得更富氮、更潮湿或更干旱，以及这些影响(由物种相互作用调节)对群落结构、多样性和生产力的影响。近邻之间的竞争通常被认为是自然选择中最强烈的力量之一，它塑造了全球植物特征的物种组成、多样性和进化。传统的理论是基于“规模优势”(SA)假说的。植物之间的激烈竞争通常选择一种包括生长到相对较大的体型的能力的策略。我的研究计划将探索一个悖论--与SA假说脱节：在几乎所有的植被类型中，大多数栖息物种都相对较小。我将开发和研究一种理解植物竞争能力的范式转变--一种认识到在竞争中适应(基因传递)不仅涉及生长(植物大小)和生存；它还涉及，最重要的是产生后代。项目将研究植物分生组织/芽的部署和分配如何影响竞争条件下适应性的所有三个组成部分--大小、生存和繁殖力。他们将测试对这三个适应度成分之间相互作用和权衡的预测，以及如何利用这些预测来定义物种共存理论的修订，这些修订不依赖于弱竞争(通过传统的生态位差异或干扰的影响)，也不需要异质的物理环境。由于分生组织生产与叶片生产直接相关，这项研究还将更广泛地发展为一系列研究，基于一种新的分生组织方法，以确定‘叶片强度’(例如，大小/数量)和‘生殖经济’(在严重的植株大小抑制下成功部署生殖分生组织的能力)方面的植物策略。这一方法将在广泛的生命形式(草本和木本)上进行测试，并在从植物内部到类群之间和跨生境类型的几个尺度上进行测试。

A fundamental goal for conservation & restoration ecology is to understand the mechanisms that explain why species composition, richness & productivity of natural vegetation vary across space & time. Answers to these questions are essential for making informed predictions and recommendations for mitigation associated with vegetation response to ongoing climate change (precipitation & temperature), atmospheric pollution (nitrogen inputs), success of invasive species, and habitat & species loss from impacts of a burgeoning human population that is destined to continue increasing in size and density in the coming decades. Faced with this, we also need to learn how to anticipate what we can expect from the emergent properties & services of the ecosystems of tomorrow as they are shaped in new ways by powerful, persistent and growing forces of anthropogenic selection. Because reproductive success of resident plants in most natural vegetation is routinely limited by near-neighbour effects, guidance in support of the above goals will require a deep understanding of the selection consequences of species interactions. Accordingly, the research program proposed here-with collaboration involving training for 9 graduate students & 15 undergraduate students-will test recent hypotheses about the key plant traits that affect success in leaving descendants in crowded vegetation (competitive ability), and under heavy impact of browsing from a continuing population explosion of white-tailed deer in eastern Ontario-and will examine the role of water versus nutrients as key objects of soil resource competition in mesic habitats that are predicted to become more nitrogen-enriched plus wetter or more arid as climate change unfolds, and as these effects (modulated by species interactions) impact on community structure, diversity and productivity. Competition between near neighbours is conventionally regarded as one of the most intense forces of natural selection that has shaped the species composition, diversity & evolution of plant traits across the globe. Traditional theory is based on a `size-advantage' (SA) hypothesis-i.e. intense competition between plants generally selects for a strategy that includes capacity to grow to a relatively large body size. My research program will explore a paradox-a disconnect with the SA hypothesis: most resident species are relatively small within virtually all vegetation types. I will develop and investigate a paradigm shift for understanding competitive ability in plants-one that recognizes that fitness (gene transmission) under competition involves more than just growth (plant size) & survival; it also involves, most importantly, producing offspring. Projects will examine how the deployment and allocation of plant meristems/buds affects all three components of fitness under competition-size, survival & fecundity. They will test predictions about interactions and trade-offs between these three fitness components, and how these can be used to define revisions for species coexistence theory that do not depend on weak competition (through traditional niche differentiation or effects of disturbance), and without requiring a heterogeneous physical environment. Since meristem production is tied directly to leaf production, this research will also develop more broadly into a series of studies based on a novel meristem-based approach for defining plant strategies in terms of 'leafing intensity' (e.g. size/number) trade-offs and 'reproductive economy' (ability to deploy reproductive meristems successfully despite severe plant size suppression). This approach will be tested across a wide range of life forms (herbaceous & woody), and at several scales ranging from within-plant to between-taxa, and across habitat types.