Role of transitory non-structural carbon reserves in boreal forest stand dynamics

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There is growing national and international interest in the underlying mechanisms of tree mortality and forest decline which have recently been associated with changes in the intensity, length and frequency of drought and climate change. Research in tree mortality has mainly focused either directly or indirectly on the processes related to moisture limitations and its impact on water transport. Moisture limitation is thought to be the main driver that cuts off the water supply to the foliage, leading to the desiccation of these tissues and ultimately to the death of trees. However, drought does not fully explain the death of trees and overall forest decline. A possible alternative explanation of this decline is carbon (C) starvation. This hypothesis suggests that due to closed stomata and reduced C assimilation trees could suffer from insufficient and depleted C reserves necessary to maintain their basic respiration needs during high and prolonged stress. This hypothesis has not been rigorously tested and empirical data that support or challenge this hypothesis are scarce. I propose to test the overarching hypothesis that during times of stress when C assimilation is limited, C reserves in tissues will play a critical role in the performance and mortality of seedlings and mature trees. Further, I will investigate various aspects of C reserve allocation to the crown, stem, and root system during and after periods of C limitation in field and controlled growth chamber studies. I will also monitor C limitation effects on processes related to regeneration and mortality. My research program will provide training for HQP in ecophysiology and forest ecology in a collaborative environment. Understanding the role of C reserves in trees could lead to the use of stored C reserves as an early indicator of stress in trees thereby serving as a risk assessment tool for determining forests' health, resiliency, and adaptability to climatic change; thus providing research vital to Canada's forests and its associated economy.