Pine mortality in southeast Spain after an extreme dry and warm year: interactions among drought stress, carbohydrates and bark beetle attack

Abstract

Key message: Pine mortality was related to water stress, which caused xylem cavitation.Hydraulic failure and carbon starvation are likely interrelated, and bark beetles attacks did not seem to be directly involved. Abstract: Forests are extremely important for society given the many services they provide. Climate models reflect increases in temperature and less annual rainfall, which will generate hotter drier environments. Under these conditions, it is predicted that forest ecosystems will be severely affected, and recent studies have accumulated evidence for drought-induced tree mortality. Consequently, many studies have attempted to explain mechanisms of survival and mortality in forest species. However, the physiological mechanisms that underlie drought mortality are not completely understood. The aim of the present study was to analyse the effect of an extremely dry year on the cause of mortality of pines and on forest decline in pine forest populations in southeast Spain. Specifically, we studied the effect of drought stress that caused pine mortality, dynamics of carbohydrates reserves and bark beetle attack. The results suggest that pine mortality can be attributed to an intense drought stress level that caused xylem cavitation. The results also indicate that hydraulic failure and carbon starvation are likely interrelated, which makes separating both mechanisms very difficult. Finally, the recorded bark beetles attack did not seem to be directly involved in mortality, at least not in the forests with less intense drought conditions.