Francis Marion National Forest
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Forest carbon assessment for the Francis Marion National Forest Alexa Dugan ([email protected]) and Duncan McKinley ([email protected]) July 22, 2019 1.0 Introduction Carbon uptake and storage are some of the many ecosystem services provided by forests and grasslands. Through the process of photosynthesis, growing plants remove carbon dioxide (CO2) from the atmosphere and store it in forest biomass (plant stems, branches, foliage, roots) and much of this organic material is eventually stored in forest soils. This uptake and storage of carbon from the atmosphere helps modulate greenhouse gas (GHG) concentrations in the atmosphere. Estimates of net annual storage of carbon indicate that forests in the United States (U.S.) constitute an important carbon sink, removing more carbon from the atmosphere than they are emitting.1 Forests in the U.S. remove the equivalent of about 12-19 percent of annual U.S. fossil fuel emissions or about 206 teragrams of carbon after accounting for natural emissions, such as wildfire and decomposition.2, 3 The Intergovernmental Panel on Climate Change (IPCC) has summarized the contributions of global human activity sectors to climate change in its Fifth Assessment Report.4 From 2000 to 2009, forestry and other land uses contributed just 12 percent of human-caused global CO2 emissions.5 The forestry sector contribution to GHG emissions has declined over the last decade.4,6,7 Globally, the largest source of GHG emissions in the forestry sector is deforestation,1,4,8 defined as the removal of all trees to convert forested land to other land uses that either do not support trees or allow trees to regrow for an indefinite period.9 However, the United States is experiencing a net increase in forestland in recent decades because of the reversion of agricultural lands back to forest and regrowth of cut forests,10 a trend expected to 1 Pan, Y., R.A. Birdsey, J. Fang, R. Houghton, P.E. Kauppi, W.A. Kurz, O.L. Phillips, et al. 2011. A large and persistent carbon sink in the world’s forests. Science 333: 988–993. 2 US EPA. 2015. US inventory of greenhouse gas emissions and sinks: 1990 – 2013. Executive Summary. EPA 430-R15-004 United States Environmental Protection Agency. Washington, D.C. 27 pp. 3 Janowiak, M., W.J., Connelly, K. Dante-Wood, G.M. Domke, C. Giardina, Z. Kayler, K. Marcinkowski, T. Ontl, C. Rodriguez-Franco, C. Swanston, C.W. Woodall, and M. Buford. 2017. Considering Forest and Grassland Carbon in Land Management. Gen. Tech. Rep. WO-95. Washington, D.C.: United States Department of Agriculture, Forest Service. 68 p. 4 IPCC, 2014: Climate Change 2014: Synthesis Report. Contribution of Working Groups I, II and III to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change [Core Writing Team, R.K. Pachauri and L.A. Meyer (eds.)]. IPCC, Geneva, Switzerland, 151. 5 Fluxes from forestry and other land use (FOLU) activities are dominated by CO2 emissions. Non-CO2 greenhouse gas emissions from FOLU are small and mostly due to peat degradation releasing methane and were not included in this estimate. 6 FAOSTAT (2013). FAOSTAT database. Food and Agriculture Organization of the United Nations, available at http://faostat.fao.org/. 7 Smith P., M. Bustamante, H. Ahammad, H. Clark, H. Dong, E.A. Elsiddig, H. Haberl, et al. 2014. Agriculture, Forestry and Other Land Use (AFOLU). In: Climate Change 2014: Mitigation of Climate Change. Contribution of Working Group III to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change [Edenhofer, O., R. Pichs-Madruga, Y. Sokona, et al. (eds.)]. Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA. 121 pp. 8 Houghton, R.A., J.I. House, J. Pongratz, G.R. van der Werf, R.S. DeFries, M.C. Hansen, et al. M.C. 2012. Carbon emissions from land use and land-cover change. Biogeosciences 9: 5125–5142. 9 IPCC 2000. Intergovernmental Panel on Climate Change (IPCC), Special Report on Land Use, Land Use Change and Forestry, Summary for Policy Makers, 2000. IPCC, Geneva, Switzerland. 20 pp. 10 Birdsey R, K. Pregitzer, and A. Lucier. 2006. Forest carbon management in the United States:1600-2100. J. Environ. Qual. 35:1461-1469. 1 continue for at least another decade.11,12 Forests are dynamic systems that naturally undergo fluctuations in carbon storage and emissions as forests establish and grow, die with age or disturbances, and re-establish and regrow. Forests release CO2 into the atmosphere when trees and other vegetation die, either through natural aging and competition processes or disturbance events (e.g., combustion from fires). This process transfers carbon from living carbon pools to dead pools, which also release carbon dioxide through decomposition or combustion (fires). Management activities include timber harvests, thinning, and fuel reduction treatments that remove carbon from the forest and transfer a portion to wood products. Carbon can then be stored in Box 1. Description of the primary forest carbon models used to commodities (e.g., paper, conduct this carbon assessment lumber) for a variable duration ranging from Carbon Calculation Tool (CCT) days to years, or, in the case of some structural Estimates annual carbon stocks and stock change from 1990 to timber, from many 2013 by summarizing data from two or more Forest Inventory decades to centuries. In and Analysis (FIA) survey years. CCT relies on allometric the absence of models to convert tree measurements to biomass and carbon. commercial thinnings, Forest Carbon Management Framework (ForCaMF) harvests, and fuel reduction treatments, Integrates FIA data, Landsat-derived maps of disturbance type forests will thin naturally and severity, and an empirical forest dynamics model, the from mortality-inducing Forest Vegetation Simulator, to assess the relative impacts of disturbances or aging, disturbances (harvests, insects, fire, abiotic, disease). resulting in dead trees ForCaMF estimates how much more carbon (non-soil) would decaying and emitting be on each national forest if disturbances from 1990 to 2011 carbon to the atmosphere. had not occurred. Following natural Integrated Terrestrial Ecosystem Carbon (InTEC) model disturbances or harvests, A process-based model that integrates FIA data, Landsat- forests re-establish and derived disturbance maps, as well as measurements of climate regrow, resulting in the variables, nitrogen deposition, and atmospheric CO2. InTEC uptake and storage of estimates the relative effects of aging, disturbance, regrowth, carbon from the and other factors including climate, CO2 fertilization, and atmosphere. Over the long nitrogen deposition on carbon accumulation from 1950 to term, through one or more 2011. Carbon stock and stock change estimates reported by cycles of disturbance and InTEC are likely to differ from those reported by CCT regrowth (if the forest because of the different data inputs and modeling processes. regenerates after the disturbance), net carbon flux (the balance from 11 USDA Forest Service. 2016. Future of America's forests and rangelands: update to the 2010 Resources Planning Act Assessment. General Technical Report WO-GTR-94. Washington, DC. 250 p. 12 Wear, D.N., R. Huggett, R. Li, B. Perryman, and S. Liu. 2013. Forecasts of forest conditions in regions of the United States under future scenarios: A technical document supporting the Forest Service 2010 RPA Assessment. US Department of Agriculture Forest Service, General Technical Report SRS-170. 2 accumulation and loss) is often zero. This happens when regrowth of trees accumulates the same amount of carbon as was emitted as a result of disturbance or mortality.13 Although disturbances, forest aging, and management are often the primary drivers of forest carbon dynamics in some ecosystems, environmental factors such as atmospheric CO2 concentrations, climatic variability, and the availability of limiting forest nutrients, such as nitrogen, can also influence forest growth and carbon dynamics.14, 15 In this section, we provide an assessment of the amount of carbon stored on the Francis Marion National Forest (baseline carbon stocks) and how disturbances, management, and environmental factors have influenced carbon storage overtime. This assessment primarily used two recent U.S. Forest Service reports: the Baseline Report16 and Disturbance Report.17 Both reports relied on Forest Inventory and Analysis (FIA) and several validated, data-driven modeling tools to provide nationally consistent evaluations of forest carbon trends across the National Forest System. The Baseline Report applies the Carbon Calculation Tool (CCT),18 which summarizes available FIA data across multiple survey years to estimate forest carbon stocks and changes in stocks at the scale of the national forest from 1990 to 2013. The Baseline Report also provides information on carbon storage in harvested wood products (HWP) for each Forest Service region. The Disturbance Report provides a national forest-scale evaluation of the influences of disturbances and management activities, using the Forest Carbon Management Framework (ForCaMF).19,20,21 This report also contains estimates of the long-term relative effects of disturbance and non-disturbance factors on carbon stock change and accumulation, using the Integrated Terrestrial Ecosystem Carbon (InTEC) model.22, 23 The key findings from these reports are summarized here. See Box 1 for descriptions of the carbon models used for these analyses. To infer future forest carbon dynamics, information from additional reports, including the most recent Resource Planning Act (RPA) assessment11 and a 13 McKinley, D.C., M.G. Ryan, R.A. Birdsey, C.P. Giardina, M.E. Harmon, L.S. Heath, et al. 2011. A synthesis of current knowledge on forests and carbon storage in the United States. Ecological Applications 21: 1902-1924. 14 Caspersen J.P., S.W. Pacala, J.C. Jenkins, G.C. Hurtt, P.R. Moorcroft, and R.A. Birdsey. 2000. Contributions of Land-Use History to Carbon Accumulation in U.S. Forests. Science 290: 1148-1151. 15 Pan Y, R.