PS 68-55 - Quantifying forest carbon dynamics as a function of tree species composition under projected climate  

Friday, August 11, 2017
Exhibit Hall, Oregon Convention Center
Rachel Swanteson-Franz, Biology, University of New Mexico, Daniel J. Krofcheck, Department of Biology, University of New Mexico, Albuquerque, NM and Matthew D. Hurteau, Biology, University of New Mexico, Albuquerque, NM

Global climate is rapidly changing and increasing temperatures and precipitation variability pose a challenge for many forest ecosystems. Determining the adaptive capacity of forests is paramount for understanding how climate change will impact ecosystem function, including carbon (C) uptake and storage. Further, understanding climate-induced changes in forest carbon dynamics can help inform management strategies to potentially maintain or build adaptive capacity. We sought to quantify how projected climate under business-as-usual emissions would influence individual species and alter forest C dynamics. Given this information, we also sought to quantify the potential for management activities to alter forest C dynamics. Given their drought tolerance and higher growth rates, we hypothesized that conifer species would have higher C storage and reducing competition with slower growing species could enhance this. We used the LANDIS-II model to run individual species and landscape simulations of the southern pine and mixed pine-hardwood forests in Fort Benning, Georgia. Landscape simulations include several management scenarios informed by the single species simulations. We evaluated Total Ecosystem Carbon (TEC) as our response variable.


Consistent with our hypothesis, conifer species stored an average 6000 g C m-2 more than hardwoods in single species simulations. The three conifer species had consistent biomass levels, until late-century when Pinus taeda sequestered 393 g C m-2 more than P. echinata and 292 g C m-2 more than P. palustris. Based on the single species results and management objectives, such as providing Red-cockaded woodpecker habitat at the installation, we simulated no-management, prescribed burning, and a thinning scenario that removed small conifers and all hardwood species. Late-century TEC in the no-management scenario (13059 gC m-2, sd 11 gC m-2) did not differ from the prescribed fire scenario (13098 gC m-2, sd 8.3 gC m-2). The thinning scenario resulted in a late-century decline in TEC (12890 gC m-2, sd 6.3 gC m-2). However, planting conifer species followed thinning treatments, late-century TEC surpassed the other scenarios by approximately 6%. Our preliminary results suggest limited competition between conifers and slower growing broadleaved species under projected climate. Furthermore, management activities, such as planting conifer seedlings, can minimize the carbon reductions associated with management for other resource objectives.