Ecosystem carbon stocks and sequestration potential of federal lands across the conterminous United States

Abstract

Federal lands across the conterminous United States (CONUS) account for 23.5% of the CONUS terrestrial area but have received no systematic studies on their ecosystem carbon (C) dynamics and contribution to the national C budgets. The methodology for US Congress-mandated national biological C sequestration potential assessment was used to evaluate ecosystem C dynamics in CONUS federal lands at present and in the future under three Intergovernmental Panel on Climate Change Special Report on Emission Scenarios (IPCC SRES) A1B, A2, and B1. The total ecosystem C stock was estimated as 11,613 Tg C in 2005 and projected to be 13,965 Tg C in 2050, an average increase of 19.4% from the baseline. The projected annual C sequestration rate (in kilograms of carbon per hectare per year) from 2006 to 2050 would be sinks of 620 and 228 for forests and grasslands, respectively, and C sources of 13 for shrublands. The federal lands' contribution to the national ecosystem C budget could decrease from 23.3% in 2005 to 20.8% in 2050. The C sequestration potential in the future depends not only on the footprint of individual ecosystems but also on each federal agency's land use and management. The results presented here update our current knowledge about the baseline ecosystem C stock and sequestration potential of federal lands, which would be useful for federal agencies to decide management practices to achieve the national greenhouse gas (GHG) mitigation goal.biogeochemical modeling | ecosystem carbon dynamics | land use and land cover | federal lands | nonfederal lands F ederal lands were established to help sustain biodiversity, manage mineral and energy development, provide recreational opportunities, oversee timber harvesting, and protect these resources from human impacts (1). The US government has direct ownership of 2.63 × 10 6 km 2 -nearly 30% of the whole national territory area. Clawson (2) stated, "Extensive federal land ownership has been an integral part of US society and economy throughout our national history." Natural resource use and deployment always involves the federal government to a greater extent on federal lands than on nonfederal lands.The federal lands across the conterminous US (CONUS) account for about 23.5% of the CONUS terrestrial area. Their areal portion varies dramatically from state to state, ranging from 84.5% in Nevada to <2% in some eastern states, but more than 90% are concentrated in the western United States.Numerous inventory-and modeling-based studies, using atmospheric (top-down) and ground-based (bottom-up) methods, have been conducted to quantify ecosystem carbon (C) stocks and changes in the United States. These studies agree on the presence of C sinks in the CONUS ecosystems (3). Changes in climate and land use exert profound effects on the ability of ecosystems to sequester atmospheric C and maintain a stable ecosystem C stock (3, 4). However, almost all studies focused on nonfederal lands or on a mixture of both private and federal lands; thus, no information about ecosystem C stoc...

Carbon stocks and stock change on federal forest lands of the United States

“…For example, Tan et al. () produced estimates that were primarily based on the FIADB; forest area and non‐soil carbon estimates were consistent with carbon from the tree and condition tables of the database. Ongoing changes through adaptation of alternate approaches, improvements, or other revisions of existing methods can add to the array of potential reported values.…”

“…Tan et al. () evaluated the potential for future carbon storage in terrestrial ecosystems on federal lands of conterminous United States. They projected continued sequestration but a slightly decreasing role of federal lands in the overall U.S. carbon budget.…”

“…The inclusions of the FIADB tables as a source are because they are publicly available and readily used to develop estimates (Tan et al. ). The mean distribution of plot‐level carbon densities is shown in Fig.…”

“…Examples where researchers obtained carbon estimates directly from the FIADB include analyses by Tan et al. (), Zhou et al. (), and Fahey et al.…”

“…Lands under federal ownership represent a large area of forest ostensibly under a single ownership but managed by separate agencies or departments. The carbon in those forests is often targeted as the basis for a variety of management, policy, or reporting purposes (Smith and Heath 2004, Smith 2012, Tan et al 2015, USDA 2016. A principal data source for many U.S. forest carbon assessments is the Forest Inventory and Analysis Data Base (FIADB; USDA Forest Service 2017), which is compiled, maintained, and made publicly available by the Forest Inventory and Analysis Program (FIA) of the United States Department of Agriculture Forest Service (Forest Service hereafter, USDA Forest Service 2018).…”