Region-Wide Soil Carbon Assessment Across "the Land of Pines"
Abstract:The US Southeast is dominated by forested ecosystems, of which nearly 85 million hectares are timberland. These forests account for more than 1/3 (~12 Pg C) of the conterminous US forest C stocks and sequester 76 Tg C annually, equivalent to 13% of the regions greenhouse gas emissions. Additionally, these forests store a substantial amount of soil organic carbon (SOC), commonly exceeding twice the carbon measured in above ground biomass. However, due to the spatial-variation of SOC, these estimates have a large degree of uncertainty.
Current projections for the region indicate a likely warmer and dryer future climate. As such, typical recurring questions are: “How vulnerable are these carbon stocks to altered climate conditions?” and “How will we measure this change without accurate baseline estimates?”
To answer these questions, PINEMAP (Pine Integrated Network: Education, Mitigation, and Adaptation Project) established a multi-tiered monitoring network to provide baseline measurements for carbon, water, and nutrient storage and fluxes in forested ecosystems across the Southeastern US. Here, we present preliminary findings from a region-wide modeling approach in an attempt to understand how various scenarios of climate change may affect carbon stocks in these ecosystems. To achieve this, the DayCent biogeochemical model was parameterized and calibrated with site-specific data from the PINEMAP Tier 3 network. Preliminary results indicate the model performed well, with an R2 = 0.86 for simulated vs observed SOC and R2 = 0.97 for simulated vs observed net primary productivity (NPP). The model is currently being scaled up to the Tier 2 network, which consists of 324 plots, to provide more representative estimates across the entire Southeastern US. The results of this transdisciplinary research project will be used to improve decisions regarding management and carbon sequestration strategies.