Minimum levels of carbon reserves in temperate trees at severe carbon limitation and drought stress

Funded by the Swiss National Foundation

Duration: 01.02.2015 - 31.01.2018

Responsible Scientists: Raphael Weber (PhD student), Sandra Schmid, PD Dr. Günter Hoch (PI), Dr. Arthur Gessler (co-PI, WSL)


A detailed understanding of the carbon (C) relations of trees is key to understand their physiological reaction to climatic change at the local and global scale. An increasing number of studies are using C reserve concentrations of plant tissues as proxies for a plant's net C balance. However, recent research has questioned the indicative value of C reserve concentrations for a plant's C relation, emphasizing the active nature of reserve formation, which can also occur against prevailing C-sink demands, and thus might be in direct competition with growth.

In this project we are aiming to (1) monitor the effects of severe shading on growth and C storage of tree saplings over the course of 2.5 years, in order to identify the reaction of non-structural C reserves to long-term C limitation. In an additional experiment, we will (2) investigate the absolute minimum concentrations of different C reserve compounds (NSC and lipids, but also cell-wall hemicelluloses as potential reserves) by exposing saplings of four different species (two deciduous broad-leaved, two evergreen conifers) to either continuous darkness or repeated defoliation until the death of the saplings due to C starvation. Finally, (3) after one growing season, a subset of shaded and un-shaded trees from the long-term shading experiment will be treated with continuous drought, in order to test the significance of the initial C reserve tissue concentrations for the survival of tree saplings under hydraulic stress.

The project will significantly contribute to close a major gap in our understanding of the C relations and C reserve dynamics in trees. Because the comparative analyses of C reserve tissue concentrations has become a widely used tool to asses the C relations of plants, the gained knowledge on the physiological minimum values of C reserve concentrations, possible growth-storage trade-offs under C limitation, and the significance of C reserves for drought survival, will be of prime importance for all researches working on the C dynamics of plants, especially with respect to climate change effects. Within this research project we will thus address fundamental, but so far largely unexplored questions regarding the dynamic of C storage in trees to better assess the potential of C reserve tissue concentrations as indicators of a plant's C balance.