Do Carbon Reserves Increase Tree Survival during Stress and Following Disturbance?

PURPOSE OF REVIEW: Carbon (C) storage provides trees with a pool of C that can be remobilized and used to sustain vital physiological processes when photosynthesis and/or C transport cannot meet a plant’s current demands. As such, it may be an important determinant of tree survival in many cases. However, we do not yet know how often tree mortality occurs as the result of carbon limitation, and therefore it remains unclear whether C storage is important for preventing tree death. The purpose of this review is therefore to summarize and assess recent research regarding the role of C storage in tree survival under different stressors and disturbances. RECENT FINDINGS: Both recent and older work have identified many potential mechanisms by which C storage may influence tree survival, and there is evidence that higher tissue non-structural carbohydrate concentrations or total content can be associated with survival and recovery following defoliation and aboveground tissue destruction and under deep shade, drought, flooding, biotic attack, and freezing temperatures. However, in most cases, there is also evidence suggesting that C storage does not always or even often influence survival. Both drought and flooding may lead to inhibition of C transport, particularly to the roots, suggesting that increased root storage specifically might play a critical role in survival; however, this remains to be tested. In some cases, the ability to maintain C assimilation and transport might be more critical than increasing storage. Though C storage can affect survival, we are far from knowing how common or uncommon this pattern is. Future work exploring the relationship between survival and storage needs to focus on measuring C storage in all organs and tissues, considering the importance of total storage content, not just concentrations, identifying the relevant compounds in different species that constitute the actual storage pool, and carefully separating out the effects of storage from other factors that also tend to change when storage concentrations are altered.