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.

Cumulative Drought Stress Leads to a Loss of Growth Resilience and Explains Higher Mortality in Planted than in Naturally Regenerated Pinus pinaster Stands

“…This loss of resilience may reflect the poor vigor of these trees, which responded to recurrent droughts by showing a reduction in growth rates and by needle shedding. These symptoms may portend widespread tree mortality, as has been observed in other drought-prone pine plantations [10]. Therefore, our results confirm an increased sensitivity of planted P. pinaster stands to drought which suggests that they will become increasingly vulnerable to drought-triggered tree mortality in the coming decades [17].…”

Tree water dynamics in a drying and warming world

“…Indeed, previous findings suggested that warming superimposed on drought is going to exacerbate the drought stress experienced by trees and could lead to more frequent drought‐associated mortality events (Williams et al ; Allen et al ; García de la Serrana et al ). However, after a period of five years under warmer (+ ≈ 5 °C) and drier (−50% precipitation) conditions, we observed no mortality or significant decline at our study site.…”

Carbon balance as affected by biosolid application in reforestations

“…It is the prevailing tree in dry and semiarid areas and broadly used in reforestation and restoration activities (Pausas et al, 2004) because of its high rates of seedling survival and growth (Barberá, Martínez-Fernández, Álvarez-Rogel, Albaladejo, & Castillo, 2005;Fuentes, Valdecantos, Cortina, & Vallejo, 2007) and its plasticity to changes in the soil environment (Broncano, Riba, & Retana, 1998). Nevertheless, its use in high water-stressed semiarid systems may be detrimental to stimulate successional processes (Bellot, Maestre, Chirino, Hernández, & De Urbina, 2004), and their adaptation may not be sufficient for future climatic scenarios (García de la Serrana, Vilagrosa, & Alloza, 2015).…”