The impacts of multi-decadal drought on tropical forest function

Patrick Meir and Sarah Ingrid Coughlin, Research School of Biology, Australian National University, Canberra, Australia, Patrick Meir, School of Geosciences, University of Edinburgh, Edinburgh, United Kingdom, Antonio CL da Costa, Ecology and Earth Sciences Division, Emílio Goeldi Museum, Belém, Brazil, Lucy Rowland, University of Exeter, Maurizio Mencuccini, Ecological and Forestry Applications Research Centre (CREAF), Autonomous University of Barcelona, Spain, Oliver Binks, School of GeoSciences, University of Edinburgh, Edinburgh, United Kingdom, Paulo R. Bittencourt, Geography, University of Exeter, Exeter, United Kingdom, David Bartholomew, Department of Geography, Unviersity of Exeter, Exeter, United Kingdom, Rafael Oliveira, University of Campinas, Brazil, Mathias Disney, Dept of Geography, UCL, London, United Kingdom, Andrew Burt, Department of Geography, University College London, London, United Kingdom, Leandro Ferreira, Museu Paraense Emilio Goeldi, Belém, Brazil

Background/Question/Methods
Drought can act over seasons to decades and beyond, with notable examples in tropical forests evident in the recent past, as well as in a range of possible futures this century. However, studying drought responses by trees and forests over ecologically meaningful timescales is challenging. This is especially true at stand scale, where both inter- and intra-specific variations in growth, drought-induced tree mortality rates and acclimation among different plant physiological traits can all influence long-term biogeochemical and ecological trajectories, with large potential global impact. As part of our attempts to address this challenge, we synthesise recent findings from the world’s only multi-decadal (20 yrs) and stand-scale (1 ha treatment) throughfall exclusion experiment in tropical forest, situated in eastern Amazonia.
Results/Conclusions
We quantify and analyse: (i) how different physiological traits (metabolic, hydraulic) exert control upon growth and how this changes during drought; (ii) how traits differ in their capacity to acclimate under long-term drought stress, and how taxonomic identity and tree size influence these processes; (iii) how new high-resolution laser-based structural analysis is transforming our quantification of metabolic, structural and growth responses to drought; and (iv) how drought alters overall water use and water stress at individual tree and stand-scale, over different timescales. The results connect a series of new findings that inform short- and long-term influences of future drought on tropical forest structure, function and composition. They also highlight the importance of accounting for diversity across physiological trait responses and species identity.