Post-fire habitat conditions as drivers of progressive and retrogressive succession: seedbed filter, species traits and feedback of dominant plants

发现扰动后群落组装和演替的驱动因素一直是生态学家长期关注的问题。可靠的演替轨迹预测是发展生态学理论和自然资源管理战略的必要条件。人们普遍认为，野火在北方森林重置演替达到高潮，火灾前的立场结构。在这种渐进式的继承中，竞争性排斥被认为是主要的驱动力。但重要的例外发生在火灾后的北方和温带针叶林与杜鹃花科林下，低严重火灾往往导致退化演替。在这里，竞争为基础的组装规则是先发制人的栖息地条件，其特征在于厚残留有机质（ROM）。我以前的工作，这样一个系统占主导地位的黑云杉（Picea mariaia）和Kalmia（Kalmia angustifolia）表明，厚厚的ROM形成贫穷的苗床云杉，但保护地下芽Kalmia迅速出现，并主导火灾后的社区和抵制树殖民。对这种杜鹃花石楠的持续时间和动态知之甚少：有些人认为它会持续几年到几十年，而另一些人则认为交替的稳定状态与群落动态和植物土壤反馈的数据很少。这方面的知识是必不可少的，以了解退化演替的机制和可持续森林管理在许多营养不良的针叶树，杜鹃花群落在大西洋两岸。我的研究计划的长期目标是了解干扰介导的群落动态，特别是优势林下和冠层物种之间的相互作用。使用黑云杉-Kalmia社区作为一个研究系统，并围绕几个当代广泛的生态概念和土地管理的挑战，在未来五年内，我的研究问题将集中在四个短期目标，1。研究火灾后残留有机物（ROM）的生物物理特性，以及如何过滤物种再生性状，2。检验群落水平性状分析如何描述演替方向和生态系统功能; 3.评估Kalmia石南的寿命和生长阶段，以及4.在杜鹃花石南中发现针叶树恢复的创新方法。本研究将i）推进我们的基础知识，生境驱动的群落组装和次生演替，ii）测试的稳定性逮捕演替或交替稳定状态介导的优势植物的种群动态，群落性状过滤和植物土壤反馈，和iii）评估生物抗性与恢复生态学。本研究将聚焦于与健康形成的原因和后果有关的几个当代生态学概念，发现与火灾严重程度相关的苗床过滤器和次生演替方向的优先效应的重要性。 本研究所提出的方法的新奇是确定功能性状多样性沿着演替轨迹，而不是传统的计算分类物种多样性和组成变化沿着时间，因为干扰。我还将通过实地测量硬性状来使用优势植物的种内性状变异性。通过将群落水平的功能性状与优势植物的响应和效应性状相结合，这种方法将使我能够提供功能解释Kalmia健康和森林动态。这种新的知识的动态和寿命的Kalmia石楠，可用于设计创新的方法，森林恢复在Kalmia石楠，这对加拿大东部的土地管理具有重要意义。 本研究将培养1名博士，3名硕士和5名HBSc学生。

Discovering the drivers of post-disturbance community assembly and succession has been a long-term preoccupation amongst ecologists. A reliable prediction of successional trajectory is essential for developing ecological theory and strategy for natural resource management. It is generally believed that wildfires in the boreal forest reset succession culminating to pre-fire stand structure. In this progressive succession competitive exclusion is thought to be the main driver. But important exceptions occur in post-fire boreal and temperate conifer forests with ericaceous understory where low-severity fires often lead to retrogressive succession. Here the competition based assembly rule is pre-empted by habitat conditions characterized by thick residual organic matter (ROM). My previous work on such a system dominated by black spruce (Picea mariaia) and Kalmia (Kalmia angustifolia) showed that thick ROM forms poor seedbeds for spruce but protects the belowground buds of Kalmia that emerge quickly and dominate the post-fire community and resist tree colonization. Not enough is known about the duration and dynamics of this ericaceous heath: some suggest it lasts for several years to several decades while others suggest alternate stable states with little data on community dynamics and plant soil-feedbacks. This knowledge is essential to understand the mechanism of retrogressive succession and for sustainable forest management in many nutrient-poor conifer-ericaceous communities on both sides of the Atlantic. The long-term goal of my research program is to understand disturbance mediated community dynamics particularly the interactions between the dominant understory and canopy species. Using black spruce-Kalmia community as a study system and framing my research questions around several contemporary broad ecological concepts and land management challenges, in the next five years I shall focus on four short-term objectives, to 1. examine the biophysical properties of post-fire residual organic matter (ROM) and how that filter species regeneration traits, 2. test how successional direction and ecosystem function can be described by community level trait analysis, 3. assess the longevity and growth phases of Kalmia heaths, and 4. discover innovative methods of conifer restoration in ericaceous heaths. This research will i) advance our fundamental knowledge on habitat driven community assembly and secondary succession, ii) test the stability of arrested succession or alternate stable states mediated by population dynamics of dominant plants, community trait filtering and plant soil feedbacks, and iii) evaluate biotic resistance in relation to restoration ecology. Focusing on several contemporary ecological concepts pertaining to causes and consequences of heath formation this research will discover the significance of fire severity related seedbed filter and priority effect on the direction of secondary succession. The novelty of the proposed approach of this study is to determine functional trait diversity along successional trajectories as opposed to the traditional calculation of taxonomic species diversity and composition change along time since disturbance. I shall also use intra-species trait variability of dominant plants by onsite measurement of hard traits. By combining community level functional traits with dominant plants' response and effect traits this approach will enable me to offer functional interpretation of Kalmia heath and forest dynamics. This new knowledge on dynamics and longevity of Kalmia heath can be used in devising innovative methods of forest restoration in Kalmia heath, which has significant land management implications for eastern Canada. This research will train 1 PhD, 3 MSc and 5 HBSc students.