Community Research and Development Information Service - CORDIS

Final Report Summary - HYDROPIT (Plasticity and adaptation of hydraulic traits to overcome climate change)

While forests continue to face pressure from expanding human populations that drive land use change and deforestation, the increase in CO2 concentration during the last two centuries and global-scale trends of rising temperature and increasing climatic variability will have progressive and cumulative effects over time on forested ecosystems. This is the case, for example, of recent episodes of drought-induced forest decline, reduced seedling recruitment and decreased primary productivity at large spatial scales in a variety of woodland and forest communities, contributing to the global reduction of the carbon sink efficiency of forests and shifts in vegetation composition. In HYDROPIT we study how trees acclimate to rapidly changing environments and the limits for adaptation. In particular, we are interested in the variability of the hydraulic structure of trees and the evolution of functional traits in response to present and novel environmental conditions: raised CO2 concentration, increase of temperature and drought.
We differentiated three different stages in HYDROPIT (attached figure): 1) the study of phenotypic variability in natural populations growing in contrasted climatic conditions; 2) the disentanglement between genetic and environmental effects in hydraulic traits using a common garden and 3) the assessment of acclimation in controlled or semi-controlled conditions, the first-ever full FACE (i.e. free-air CO2 enrichment), glasshouse experiment with a wide range of growing temperatures and a whole tree chamber experiment simulating a heat wave.
Our work has started with an extensive review of drought induced tree mortality. Xylem hydraulic failure by cavitation clearly appears now as a major factor causing or triggering tree mortality during extreme drought. Now there are tools available for exploring further tree cavitation resistance more globally, across species, biomes and also at the intraspecific level. In this sense, we have contributed to the extensive debate of methods to measure embolism formation in woody plants to provide reliable techniques with a sound methodological basis which allow the use of hydraulic traits in ecological and genetic studies broadening the scope of plant hydraulics.
Our results show that global patterns of variation of functional traits with water availability are not always shown at the intraspecific level, that is within populations of a single species. Whereas the vulnerability of the hydraulic system to drought induced cavitation is linked to the mean annual precipitation in the origin of the species, and species of drier areas can sustain more tension in the xylem, populations of the same species show little variation in this trait. However, these populations differ in other traits related to evaporation rate, water acquisition and water storage. To which extend the ongoing rapid changes in the environment such as the increased occurrence of extreme droughts and heatwaves with the concomitant reduction of water potential will risk some populations will depend if they are able to adjust the minimum water potential within a range preventing mortality. Finally, our studies in predicted future environmental conditions have shown that leaves are more responsive than the hydraulic system of stems.
We have assessed causal links between the species distribution ranges and the environmental characteristics. From this point we are trying to infer which will happen in the future with natural distribution and how net primary production will change. These aspects are relevant for society, biodiversity and also to decision-making in biodiversity conservation strategies and forestry companies in order to enhance integration of adaptive strategies in forest management planning.

Contact details: Rosana López. Universidad Politécnica de Madrid. Email: rosana.lopez@upm.es
More information about the project can be found in:
https://rosanalopezrodriguez.wordpress.com/

Related information

Documents and Publications

Reported by

INSTITUT NATIONAL DE LA RECHERCHE AGRONOMIQUE
France

Subjects

Life Sciences
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