Role of carbon reserves in tree and forest mortality

随着气候变化，森林死亡预计将变得更加频繁。我们预测这些事件的能力很差，因为我们缺乏关于树木死亡的潜在生理机制的知识。具体地说，非结构性碳水化合物的碳储量(糖和淀粉)参与了植物几乎所有的关键生理过程，但这些碳储量在树木的生存和死亡中所起的作用仍然是争论的热点。*我的长期研究目标是了解控制森林动态和森林生态系统发展的潜在过程。通过拟议的研究计划，我将检验最重要的假设，即在胁迫时期，当碳同化(光合作用)受到限制时，储量分配的变化可能导致特定组织或器官中的低碳储量，这反过来将在树木的表现和潜在的死亡中发挥关键作用。在接下来的五年里，我将培养3名博士和2名硕士。1.碳水化合物分配是一个自上而下的过程(例如，需要碳储备的汇接近源头(树叶)将首先获得它们的储备)。*2.高大树木的森林衰退是自上而下分配的结果，其中根部将首先受到来自树冠的碳供应的减少的负面影响。*3.储存的储备可以从储存组织中重新调动，但它受到存储来源距离的控制，因此a)离需要位置最近的存储首先被重新动员，b)一个器官中存储的碳在很大程度上不能被其他器官获得。*该计划还将与建立全球元数据集的更大国际努力相联系，这将使我们能够探索包括碳储量在内的功能树特征在广泛的森林类型和气候中对它们的生长和生存所起的作用。我的计划将使用最先进的分析设备和协议，将大田和受控温室研究与成熟和幼树结合起来。这一结果将是对树木碳储量重要性的独特表征，这将从根本上促进我们对碳储量储存机制和策略的理解，以及它们在长寿植物抗逆性中的重要性。总体而言，这项研究计划将建立所需的基础科学知识，以改善对加拿大森林和其他地区气候变化的森林死亡预测。

Forest die-off is predicted to become more frequent with climate change. Our ability to predict these events is poor because we lack knowledge about the underlying physiological mechanisms of tree mortality. Specifically, nonstructural carbohydrate carbon reserves (sugars and starch) are involved in almost all critical physiological processes in plants, yet it remains hotly debated what role these carbon reserves play in the survival and mortality of trees.****My long-term research objective is to understand the underlying processes controlling forest dynamics and forest ecosystem development. With the proposed research program I will test the overarching hypothesis that during times of stress, when carbon assimilation (photosynthesis) is limited, shifts in reserve allocation could lead to low carbon reserves in specific tissues or organs which in turn will play a critical role in the performance and potentially in the mortality of trees. Over the next five years, I will train 3 PhD and 2 M.Sc. students, as well as several undergraduates to investigate the following hypotheses in carbon reserve allocation of plants: *******1. Carbohydrate allocation is a top-down process (e.g. sinks requiring carbon reserves closes to the source (leaves) will receive their reserves first).****2. Forest decline in tall trees is a consequence of top-down allocation, where roots will be affected negatively first (starved) by reduced carbon supply from the crown.****3. Stored reserves can be remobilized from storage tissues, but it is controlled by the distance of the storage source such that a) stores closest to location of need are remobilized first, and b) stored carbon in one organ is largely unavailable to other organs.****This program will also be linked to a larger international effort to build a global meta-data set that will enable us to explore what the role functional tree traits, including carbon reserves, play in their growth and survival across a wide range of forest types and climates. My program will combine field and controlled greenhouse studies with mature and juvenile trees using state-of-the-art analytical equipment and protocols. The results will be a unique characterization of the importance of carbon reserves in trees which will fundamentally advance our understanding of the mechanisms and strategies involved in the storage of carbon reserves and their importance in stress tolerance in long-lived plants. Overall, this research program will establish the foundational scientific knowledge required to improve upon the prediction of forest mortality in response to a changing climate for Canadian forests and beyond.***