Water Fluxes from Leaf to Ecosystem Scales in a Seasonal Mexican Cloud Forest: Implications for Climate Change Impacts and Future Research Priorities

Tuesday, 16 December 2014
Heidi Asbjornsen1, Sybil G. Gotsch2, Greg R Goldsmith3, Maria Susana Alvarado-Barrientos4, Friso Holwerda4, Leendert A. Bruijnzeel5 and Todd E Dawson6, (1)University of New Hampshire Main Campus, Durham, NH, United States, (2)Franklin and Marshall College, Lancaster, PA, United States, (3)Oxford University, Environmental Change Institute, Oxford, United Kingdom, (4)Universidad Nacional Autonoma de Mexico, Centro de Ciencias de la Atmósfera, Mexico City, Mexico, (5)VU University, Earth and Life Sciences, Amsterdem, Netherlands, (6)University of California Berkeley, Center for Stable Isotope Biogeochemistry, Berkeley, CA, United States
The ecohydrological functioning of cloud forests is intricately linked to unique plant ecophysiological traits and processes that influence water fluxes at the plot to ecosystem scales. However, despite substantial gains in our understanding of cloud forest plant ecophysiology over the past decade, integration of water flux information from the leaf to the watershed scale is still lacking. We present a synthesis of research aimed at revealing the linkages between plant ecophysiology and forest ecohydrological functioning, conducted in a seasonal cloud forest in Veracruz, Mexico. A variety of species-specific leaf-level water flux behaviors were found to influence various aspects of plant water relations, which in turn, scaled up to impact stand water balance. For example, foliar fog absorption compensated for approximately 9.3 ± 1.2% of transpiration, and nocturnal transpiration for dominant tree species during the dry-season accounted for 22% to 30% of daytime transpiration. Further, the presence of dense fog, light fog, and cloud cover was shown to reduce transpiration such that annual transpiration may increase up to 17% in the case that all fog occurrence is replaced by clear sky conditions. We discuss how these processes affect whole-plant and stand water balances, as well as the potential feedbacks of vegetation controls on hydrologic fluxes under future climate change. After placing our findings within a global context we present a conceptual model of the links between plant ecophysiological and ecosystem hydrological functioning in cloud forest settings. Finally, critical areas for future research are highlighted to further improve our understanding of the linkages between leaf- and ecosystem-level processes and fluxes.