Forest mortality can lead to irreversible change in vegetation cover, thereby affecting many processes pertinent to water, carbon, and nutrient budgets. Multiple studies have noted close association of forest mortality with water and heat stress. However, a quantitative assessment of the influence of individual and concurrent changes in precipitation, temperature, specific humidity and CO2 concentration, has not been done. The goals of this study are to evaluate the individual and combined influence of projected changes in precipitation amounts and their seasonal distribution, mean air temperature, specific humidity, and atmospheric CO2 concentration on tree mortality risks. The risk is evaluated based on the probability of days with occurrence of either hydraulic failure or stomatal closure, two physiological states contributing to dieback and eventual mortality. Alternative quantifications of risk that account for stress duration and severity are also considered to test the robustness of the analysis.
Model results show that the risk is predicted to significantly increase due to changes in precipitation and air temperature regime for the period 2050–2069. However, this increase may largely get alleviated by concurrent increases in atmospheric specific humidity and CO2 concentration. The increase in mortality risk is expected to be higher for needleleaf forests than for broadleaf forests, as a result of disparity in hydraulic traits. These findings will facilitate decisions about intervention and management of different forest types under changing climate.
Kumar, M., Y. Liu, A. Parolari, C.-W. Huang, G.G. Katul, A.M. Porporato (2018): Potential impacts of climate change on tree mortality risk: Do plant hydraulic traits matter?. American Geophysical Union 2018 Fall Meeting, Washington, DC, 10-14 Dec 2018.