B087-05
Photosynthetic acclimation to whole ecosystem warming and elevated CO2 in two peatland shrub species: implications for ecosystem modeling

Monday, 14 December 2020: 16:16
Virtual
Eric J Ward1, Mirindi Eric Dusenge2, Jeff Warren3, Anthony W King3, Daniel M Ricciuto3, Danielle Way2, David McLennan4, Bridget K. Murphy2, Artur Stefanski5, Marisol Cruz Aguilar6, Raimundo Bermudez Villanueva5, Rebecca Montgomery7, Peter B. Reich8, Stan Wullschleger9 and Paul J Hanson10, (1)U.S. Geological Survey, Wetland and Aquatic Research Center, Lafayette, LA, United States, (2)University of Western Ontario, London, ON, Canada, (3)Oak Ridge National Laboratory, Environmental Sciences Division and Climate Change Science Institute, Oak Ridge, TN, United States, (4)Oak Ridge National Laboratory, Oak Ridge, TN, United States, (5)University of Minnesota Twin Cities, Minneapolis, MN, United States, (6)Universidad de los Andes, Bogota, Colombia, (7)University of Minnesota Twin Cities, Dept. of Forest Resources, Saint Paul, MN, United States, (8)University of Minnesota Twin Cities, Department of Forest Resources, St. Paul, MN, United States, (9)Oak Ridge National Laboratory, Climate Change Science Institute, Environmental Science Division, Oak Ridge, TN, United States, (10)Oak Ridge National Laboratory, Climate Change Science Institute and Environmental Sciences Division, Oak Ridge, TN, United States
Recorded Presentation
Abstract:
Predictions of vegetation responses to global change depend on the functional form of those responses in terrestrial biosphere models and the specific parameterization of those responses. However, direct evidence of the degree of acclimation to global change factors over multiple years in vegetation grown under field conditions is rare. Here we examine the photosynthetic acclimation of two widely distributed boreal peatland shrub species to whole ecosystem warming (WEW) and elevated atmospheric [CO2] (eCO2) in the Spruce and Peatland Responses Under Changing Environments (SPRUCE) project. SPRUCE is a large-scale, long-term experiment that uses 10 open-top enclosures (12.8-m diameter) to increase air and soil temperatures to a range of targets (+0 °C, +2.25 °C, +4.5 °C, +6.75 °C, +9 °C) under both ambient and elevated (+500 ppm) CO2 concentrations. After two years of WEW and one year of eCO2, in June and August of 2017, we estimated maximum rates of Rubisco carboxylation (VCmax) and electron transport (Jmax) at five different temperatures in Chamaedaphne calyculata [(L.) Moench] and Rhododendron groenlandicum [(Oeder) Kron & Judd] in each plot, using over 580 individual response curves. We found divergent responses in the two species to WEW and eCO2 treatments. C. calyculata exhibited thermal acclimation of both VCmax and Jmax in the mid-growing season (August), but not in June, with the thermal optimum of both parameters increasing with WEW temperature. No interaction of this response with eCO2 and no change in basal rates of either parameter (i.e. measured at 25oC) were observed in this species. R. groenlandicum exhibited no acclimation to WEW, but did exhibit a decrease in VCmax at 25oC in both months in acclimation to eCO2. We conclude with a discussion of how these results will be incorporated into a specific terrestrial biosphere model (ELM-SPRUCE) and the likely impacts on predictions of ecosystem response to global change.
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