Potential future dynamics of carbon fluxes and pools in New England forests and their climatic sensitivities: A model-based study

Projections of terrestrial carbon (C) dynamics must account for interannual variation in ecosystem C exchange associated with climate change, increasing atmospheric CO2 concentration, and species dynamics. We used a dynamic ecosystem model to (i) project the potential dynamics of C in New England forests under nine climate change scenarios (CCSs) for the 21st century and (ii) examine the sensitivity of potential C dynamics to changes in climate and atmospheric CO2 concentration. Our results indicated that forest net primary productivity (NPP) and soil heterotrophic respiration (RH) averaged 428 and 279gC/m(2)/yr and New England forests sequestered CO2 by 149gC/m(2)/yr in the baseline period (1971-2000). Under the nine future CCSs, NPP and RH were modeled to increase by an average rate of 0.85 and 0.56gC/m(2)/yr(2) during 1971-2099. The asymmetric increase in NPP and RH resulted in New England forests sequestering atmospheric CO2 at a net rate of 0.29gC/m(2)/yr(2) with increases in vegetation and soil C. Simulations also indicated that climate warming alone decreases NPP, resulting in a net efflux of C from forests. In contrast, increasing precipitation by itself stimulates CO2 sequestration by forests. At the individual cell level, however, changes in temperature or precipitation can either positively or negatively affect consequent C dynamics. Elevation of CO2 levels was found to be the biggest driver for modeled future enhancement of C sequestration. Without the elevation of CO2 levels, climate warming has the potential to change New England forests from C sinks to sources in the late 21st century. Key Points <list list-type="bulleted" id="gbc20135-list-0001"> <list-item id="gbc20135-li-0001">Carbon sequestration in New England forests <list-item id="gbc20135-li-0002">Complexity of climatic sensitivities of carbon dynamics <list-item id="gbc20135-li-0003">Future potential carbon dynamics