Carbon sequestration efficiencies of six early-successional deciduous species in response to atmospheric CO2 and soil moisture treatments

Abstract

Early successional deciduous trees are an important component of many ecological restoration projects in Canada and are now often used in fire prone areas. As rising atmospheric CO2 concentrations drive changes in climate, the long-term success of these projects depends on our ability to select and propagate species that can successfully adapt. We examined ecophysiological responses of six early successional deciduous tree species from three genera in response to a 2 x 2 factorial of CO2 and soil moisture treatments. One year-old seedlings of gray birch (Betula populifolia), white birch (B. papryifera), pin cherry (Prunus pennsylvanica), choke cherry (P. virginiana), red oak (Quercus rubra) and bur oak (Q. macrocarpa) were planted in a low-nutrient medium, and subjected to ambient (400ppm) or elevated (800ppm) CO2 and irrigated (10-15% moisture content) or droughted (3-8% moisture content) soil moisture treatments for two years in a greenhouse environment. Various growth traits were examined along with biochemical efficiency and gas exchange traits including assimilation at 600 ppm CO2 (A600), stomatal conductance (Gwv600) intrinsic water use efficiency (iWUE600), and maximum carboxylation rate (Vcmax). A subset of seedlings was administered additional fertilizer treatments during the study’s 2nd year. After two years, elevated CO2 did not affect growth traits but resulted in a downregulation of Vcmax and A600 for most species. Drought resulted in lower heights, biomasses and Gwv600 values but increased Vcmax and iWUE600. Significant interactions with genus and or species were commonly observed. Additional fertilizer increased Vcmax, A600, and stomatal conductance, with growth responses differing by genus. Differing responses to elevated CO2 between years one and two indicate that trees become acclimatized overtime.