Attributing carbon changes in conterminous U.S. forests to disturbance and non‐disturbance factors from 1901 to 2010

Abstract

[1] Recent climate variability (increasing temperature, droughts) and atmospheric composition changes (nitrogen deposition, rising CO 2 concentration) along with harvesting, wildfires, and insect infestations have had significant effects on U.S. forest carbon (C) uptake. In this study, we attribute C changes in the conterminous U.S. forests to disturbance and non-disturbance factors with the help of forest inventory data, a continental stand age map, and an updated Integrated Terrestrial Ecosystem Carbon Cycle model (InTEC). We grouped factors into disturbances (harvesting, fire, insect infestation) and non-disturbances (CO 2 concentration, N deposition, and climate variability) and estimated their subsequent impacts on forest regrowth patterns. Results showed that on average, the C sink in the conterminous U.S. forests from 1950 to 2010 was 206 Tg C yr À1 with 87% (180 Tg C yr À1 ) of the sink in living biomass. Compared with the simulation of all factors combined, the estimated C sink would be reduced by 95 Tg C yr À1 if disturbance factors were omitted, and reduced by 50 Tg C yr À1 if non-disturbance factors were omitted. Our study also showed diverse regional patterns of C sinks related to the importance of driving factors. During 1980-2010, disturbance effects dominated the C changes in the South and Rocky Mountain regions, were almost equal to non-disturbance effects in the North region, and had minor effects compared with non-disturbance effects in the West Coast region.

Quantitative simulation of C budgets in a forest in Heilongjiang province, China

“…Disturbances periodically released large amounts of C to the atmosphere and further changed stand age structures. Our study showed that NEP in Heilongjiang forests was greatly influenced by disturbance factors, which is consistent with previous studies (Zhang et al 2012). Reducing the occurrence of disturbances, particularly fire, will maintain a high level of NEP in Heilongjiang.…”

“…The parameters of the InTEC model were first calibrated in that study, and then the parameters were calibrated further for China . Recently, the InTEC model was used to estimate the C balance in forest ecosystems of the United States (Zhang et al 2012. Most of the parameters used in this study were obtained from previous studies, including the maximum carboxylation rate (Vcmax), specific leaf area (SLA), sensitivity of the N fixation rate to temperature (QNfix), sensitivity of electron transport to temperature (ajm), sensitivity of Rubisco activity to temperature (avm), and actual leaf nitrogen content (Nl).…”

“…The Integrated Terrestrial Ecosystem Carbon (InTEC) model is a process-based biogeochemical model produced by Chen et al (2000a) that integrates the effects of both disturbance and nondisturbance factors in long-term C budget simulations (Chen et al 2000a, 2000b, 2000c, Zhang et al 2012.…”

Past and prospective carbon stocks in forests of northern Wisconsin: a report from the Chequamegon-Nicolet National Forest Climate Change Response Framework

“…The InTEC model is process-based, closely calibrated to FIA and other observational data, and validated at the regional scale (Box 3) (Zhang et al 2012). For northern Wisconsin we used a simple downscaling approach by extracting results based on the geographic boundary of Ecoregion 212 (Fig.…”

“…We used the Integrated Terrestrial Ecosystem Carbon Cycle Model (InTEC) to quantify the historical effects of disturbance factors (harvesting, fire, insect infestation) and nondisturbance factors (CO 2 concentration, N deposition, climate variability) on productivity and carbon stocks of the continental United States, including northern Wisconsin (Chen et al 2000a(Chen et al , 2000bZhang et al 2012). The InTEC model is process-based, closely calibrated to FIA and other observational data, and validated at the regional scale (Box 3) (Zhang et al 2012).…”