DRIMNational ProjectsJan 2011 to Dec 2013

DRIM: understanding the mechanism of drought-induced mortality in trees

Drought-induced tree mortality is emerging as a global phenomenon, and it is likely to increase in the future as a result of climate change, particularly in water-limited regions such as the Mediterranean. 

Introduction

Tree mortality episodes linked to extreme climatic events have profound demographic implications and, in some cases, will result in shifts in the distribution of forest species in relatively short periods of time. 
 
As a result, there will be changes in the structure and functioning of ecosystems, as well as in the services they provide to society. 
 
If we are to predict those changes, as well as their feedbacks to the drivers of global environmental change, we need to understand the factors that determine the vulnerability of different species to changes in environmental conditions.

 

Conclusions

Three different physiological mechanisms have been proposed to explain drought-induced mortality in trees: hydraulic failure (HFH), carbon starvation (CSH) and phloem impairment (PIH).

While there is convincing support for the HFH for some species, the support of the CSH remains tentative and the validity of this hypothesis has been recently put into question. The PIH is a new hypothesis we develop in this proposal.

Our main aim is to test these three different hypotheses and characterize the combinations of species and environmental conditions under which each of them is more likely to occur.

In order to achieve that we propose to combine three different approaches: observational studies and experimental manipulations in field populations currently suffering drought-induced mortality, detailed studies in the greenhouse under more controlled conditions, and a realistic modelling of phloem transport in trees incorporating xylem-phloem interactions.