Thursday, August 9, 2018: 8:40 AM
348-349, New Orleans Ernest N. Morial Convention Center
Bradley Christoffersen1, Charlotte Grossiord2, Chonggang Xu3, Heidi Asbjornsen4, Chris Baraloto5, Z. Carter Berry6, Damien Bonal7, Jeffrey Chambers8, Danielle Christianson9, Matteo Detto10, Boris Faybishenko11, Rosie Fisher12, Clarissa Fontes13, Claire Fortunel14,15, Kolby Jardine16, Ryan Knox17, Charles D. Koven18, Lara M Kueppers18, Nathan McDowell19, Jose A Medina-Vega20, Georgianne W. Moore21, Robinson Negron-Juarez17, Clément Stahl22, Charuleka Varadharajan23, Jeffrey M. Warren24, Brett T. Wolfe25, S. Joseph Wright26, Tana E. Wood27 and Aura M. Alonso-Rodriguez28, (1)University of Texas Rio Grande Valley, (2)Earth and Environmental Sciences Division, Los Alamos National Laboratory, Los Alamos, NM, (3)Earth and Environmental Sciences, Los Alamos National Laboratory, Los Alamos, NM, (4)Department of Natural Resources and the Environment, University of New Hampshire, Durham, NH, (5)Inra, INRA-UMR, Kourou, French Guiana, (6)Natural Resources and the Environment, University of New Hampshire, Durham, NH, (7)UMR Silva, Université de Lorraine, AgroParisTech, INRA, Nancy, France, (8)Earth Sciences Division, Climate Sciences Department, Lawrence Berkeley National Laboratory, Berkeley, CA, (9)Lawrence Berkeley National Lab, (10)Ecology and Evolutionary Biology, Princeton University, Princeton, NJ, (11)Lawrence Berkeley National Laboratory, Berkeley, CA, (12)Climate & Global Dynamics, National Center for Atmospheric Research, Boulder, (13)Integrative Biology, UC Berkeley, Berkeley, CA, (14)Department of Integrative Biology, University of Texas at Austin, Austin, TX, (15)UMR AMAP, Institut de Recherche pour le Développement, Montpellier, France, (16)Earth Sciences Division Climate Sciences Department, US Department of Energy, Berkeley, CA, (17)Earth Sciences Division, Lawrence Berkeley National Lab, (18)Earth and Environmental Sciences Area, Lawrence Berkeley National Laboratory, Berkeley, CA, (19)Atmospheric Sciences & Global Change, Pacific Northwest National Laboratory, Richland, WA, (20)Forest Ecology and Forest Management Group, Wageningen University, Wageningen, Netherlands, (21)Department of Ecology and Conservation Biology, Texas A&M University, College Station, TX, (22)Joint Research Unit Ecology of Guiana Forests, CIRAD, Kourou, French Guiana, (23)Earth and Environmental Sciences Area, Lawrence Berkeley National Lab, Berkeley, CA, (24)Environmental Sciences Division and Climate Change Science Institute, Oak Ridge National Laboratory, Oak Ridge, TN, (25)School of Natural Resources and Management, Louisiana State University, Baton Rouge, LA, (26)Smithsonian Tropical Research Institute, Panama, (27)International Institute of Tropical Forestry, USDA Forest Service, Rio Piedras, PR, (28)Sabana Field Station, International Institute for Tropical Agriculture, Luquillo, PR
Background/Question/Methods Tropical forest responses to moisture remain poorly understood, in part because of the large diversity of plant hydraulic traits found therein. Changing moisture regimes, such as more frequent drought events, are expected to interact with these diverse hydraulic traits and other requirements of tropical trees in complex ways, making prediction of ecosystem-scale responses and community compositional trajectories difficult. A first step towards discerning such responses is in the analysis of how plant hydraulic and edaphic conditions control trajectories of individual trees’ water use over pre-drought, drought, and recovery periods. We took advantage of the 2015-2016 ENSO event, which induced drought over much of the tropics, to collect sap flow data on 47 canopy and numerous sub-canopy trees across nine sites in Latin America varying in annual precipitation from 1700 mm to > 3000 mm. This enabled us to determine a range of responses to changes in moisture, both atmospheric (VPD) and in soil. Where available, via measurements on conspecific individuals or species-mean values in trait databases, plant hydraulic traits were associated with individual sap flux trajectories, in addition to site-specific soil properties and climate.
Results/Conclusions
We found a large heterogeneity of sap flow responses during the ENSO within and among study regions. The diversity of strategies to deal with drought stress was partially explained by species functional traits, background climate and intensity of soil water depletion during the ENSO. Preliminary simulations of drought responses using the Community Land Model coupled to the hydraulically-enabled Functionally Assembled Terrestrial Ecosystem Simulator (CLM-FATES-Hydro) were used to demonstrate multiple mechanisms, both edaphic- and plant trait-related, responsible for the divergence in observed sap flow responses, as well as highlight critical field measurements needed to discern among these mechanisms.
