Life of Scots pine at the xeric edge: balancing the risk of hydraulic failure and carbon starvation

Yann Salmon

University of Helsinki, Finland

University of Edinburgh, UK

yann.salmon@helsinki.fi

Mortality of trees as a result of drought has become a major research focus, and two main underlying physiological mechanisms have been proposed: carbon starvation and hydraulic failure. However, their relative importance and interaction remains poorly understood. To improve our understanding of drought-induced mortality, physiological response of co-occurring healthy and unhealthy Scots pines to summer drought were studied at the xeric edge of the species distribution. Particular attention was given to the physiological response of leaves to drought since they are the site of both photosynthesis and transpiration, and hence play key roles in balancing the risks of carbon starvation and hydraulic failure. While healthy trees showed a typical response to drought for an isohydric species, atypical physiology associated with high water losses in unhealthy trees appears to be driven by the need to maintain carbohydrate availability in needles and twigs. However this was insufficient to maintain whole tree C-balance, since unhealthy trees had lower carbohydrate reserve and higher respiration at the trunk level. These responses help to explain the interaction between carbon-starvation and risks of hydraulic failure in dying trees and were used to parameterize a process-based model of tree mortality

Recent publications:

Mencuccini M, Minunno F, Salmon Y, Martínez-Vilalta J, Hölttä T. (2015) Coordination of physiological traits involved in drought-induced mortality of woody plants. New Phytologist. DOI:10.1111/nph.13461.

Salmon Y, Barnard RL, Buchmann N. (2014) Physiological controls of the isotopic time lag between leaf assimilation and soil CO2 efflux. Functional Plant Biology. 41:850-9.

Salmon Y, Torres-Ruiz JM, Poyatos R, Martinez-Vilalta J, Meir P, Cochard H, Mencuccini M (2015) Balancing the risks of hydraulic failure and carbon starvation: a twig scale analysis in declining Scots pine. Plant, Cell & Environment. DOI:10.1111/pce.12572.