Periodic Reporting for period 2 - DISTRESS (Understanding the mechanisms behind tree responses to drought-induced stress with increasing tree size)
Período documentado: 2021-12-16 hasta 2022-12-15
DISTRESS aimed at (1) testing whether trees adjust different structural and functional traits to compensate for the predicted negative effect of height on G and Ψleaf, and (2) describing the mechanisms behind these adjustments and the potential interactions with other functional processes that may impair tree response to drought stress with increasing size. To achieve these goals, height-driven changes in multiple functional traits were assessed to test whether tall trees are more vulnerable to drought and evaluate how compensatory responses and trade-offs among traits may influence height-driven patterns in tree drought responses (WP1). In addition, the SAPFLUXNET database was used to perform a global-scale analysis of sap flow and G responses to VPD as a function of tree height (WP2). This analysis complements the approach in WP1, which used ‘static’ functional traits, by providing a more dynamic perspective on whole-tree responses to atmospheric drought. This integrated analysis has improved our understanding of the role that height plays in water-use regulation and tree vulnerability to drought. This knowledge may be used to improve mechanistic models of tree response to climatic variability. Such information is essential to better simulate the impact that climate change may have on forest ecosystems and thus adapt forest management strategies.
Work during the MSCA’s return phase at the Centre for Research on Ecology and Forestry Applications (CREAF; 12/2021 – 12/2022) involved working on sap flow data from the global dataset SAPFLUXNET (WP2). The effect tree height has on sap flow rates per tree and per sapwood (i.e. living section of the wood) area and G, as well as on their response to VPD, was assessed within and across species. Tree height has a significant effect on transpiration, although this effect is stronger at the tree level than on a per sapwood area basis. Taller species have greater water fluxes. At the intra-specific level, total sap flow per tree increases with tree height, while height-related changes in G and sap flow per sapwood area were highly species-specific. Transpiration increases with VPD were stronger in taller trees, while G decreased with VPD more steeply in shorter ones.
Results from this project were disseminated through four scientific manuscripts (three with the fellow as first author, two in preparation and one under review at the reporting time) as well as through oral presentations at international conferences (two), internal (three) and external (one) seminars and the 2022 European Researchers’ Night.