The relevance of temporal and spatial distribution of water supply in tropical forest trees

Oliver Binks, Australian National University, Maurizio Mencuccini, Ecological and Forestry Applications Research Centre (CREAF), Autonomous University of Barcelona, Spain, Lucy Rowland, University of Exeter, Antonio CL da Costa, Ecology and Earth Sciences Division, Emílio Goeldi Museum, Belém, Brazil, Paulo R. Bittencourt, Geography, University of Exeter, Exeter, United Kingdom, Steel Silva Vasconcelos, Embrapa Eastern Amazon, Belem, Brazil, Rafael Oliveira, University of Campinas, Brazil, Ingrid Coughlin and John Finnigan, Biology, Australian National University, Canberra, ACT, Australia, Mathias Disney, Dept of Geography, UCL, London, United Kingdom, Kim Calders, University of Ghent, Ghent, Belgium, Patrick Meir, School of Geosciences, University of Edinburgh, Edinburgh, Scotland

Background/Question/Methods
Dew is a minute fraction of the annual water input to rainforests but may contribute disproportionately to transpired water by virtue of being in the right place at the right time. Therefore, while the rates of water taken up via foliar water uptake (FWU) tend to be low, regular inputs of dew may result in a vital ‘trickle charge’ of water to the forest canopy during the driest part of the year. Here I bring together detailed research on the uptake of atmospheric water by leaves with profiles of canopy wetness to quantitatively evaluate the interacting roles of FWU and dew formation in the water budget of an Amazonian rainforest canopy.
Results/Conclusions
Our results show that dew increases the duration of dry season canopy wetness by over 50 % in a seasonally dry Eastern Amazon field site, and that water taken up via FWU could account for 8 % of total annual transpiration. We therefore suggest that the frequent occurrence of dew events in the dry season, coupled with the capacity for canopy-level foliar water uptake, may account for a significant, regular, and potentially vital, source of water.