Transitions and thresholds in global ecological changes of forest ecosystems

全球生态变化正在对森林生态系统产生意想不到的影响，气候变化）与自然扰动机制的相互作用在很大程度上是未知的。这部分是由于经验分析不足，部分是由于阈值行为建模不足。我们从实证和建模的角度研究了各种影响-从个人到人口到景观的尺度。主要目标是提高我们对空间和时间动态的理解，包括预测树木、树木种群和森林动态在面临压力和干扰时的“关键”转变。我们的研究计划的一个目标是检查树（主要是树木年代学）和森林（通过古花粉）的数据和探索“早期预警系统”使用既有和新的分析（统计）工具，以帮助检测过渡，关键和非关键。另一方面，我们将在种群和生态系统层面建立基于过程的模型，以帮助更好地理解一些新情景下的这些转变，密切关注最近发现的树木阈值行为。很少有工作已经做了链接统计工具，以检测关键的过渡与基于过程的模型，突出了我们的工作的新奇。更紧密地结合经验和理论的方法来理解压力和干扰对森林动态的影响，将推动生态学领域的发展，提高我们对森林生态系统的基本认识，并为管理决策提供信息。我们的研究，这将有助于确定在哪些条件下发生突变，以及它们是否是“关键”，可以帮助准备或避免未来的意外生态系统的反应。虽然新的实地研究将集中在加拿大和巴西，但发现将适用于全球，因为理论，统计和建模方法更普遍，可以很容易地适应当地的研究/物种。

Global ecological changes are having unexpected effects on forest ecosystems and understanding of how various human-induced stressors (e.g., climate change) interact with natural disturbance regimes is largely unknown. This is partly due to insufficient empirical analysis and partly due to insufficient modeling of threshold behavior. We examine a variety of effects -– at scales from individuals to populations to landscapes -– from both empirical and modeling perspectives. The main objective is to improve our understanding of spatial and temporal dynamics, including predicting “critical” transitions in tree, tree population and forest dynamics in the face of stress and disturbances. One objective of our research program is to examine tree (largely dendrochronological) and forest (through paleopollen) data and explore ‘early-warning systems' using both established and new analytical (statistical) tools to help detect transitions, both critical and non-critical. On the other hand we will build process-based models at the population and ecosystem level to help better understand these transitions under a number of new scenarios, paying close attention to recently discovered threshold behaviour of trees. Little work has been done to link statistical tools available to detect critical transitions with process-based models which highlights the novelty of our work. A closer integration of empirical and theoretical approaches to understanding stress and disturbance effects on forest dynamics will advance the field of ecology, improve our fundamental understanding of forest ecosystems and inform management decisions. Our studies, which will help to determine under which conditions abrupt changes occur, and whether or not they are ‘critical', could help to prepare for or avert future surprises in ecosystem response. Though the new field studies will focus on Canada and Brazil, discoveries will be applicable worldwide because the theoretical, statistical and modelling approaches are more general and can be easily adapted to local studies/species.**