What is the role of forests in the US carbon balance?
Carbon Cycles In Western Forests Saf 5 1 2009
Carbon Cycles in Western Forests Michael G. Ryan Michael A. Battaglia USDA Forest Service Rocky Mountain Research Station Fort Collins, CO 80526 [email_address] firstname.lastname@example.org http://lamar.colostate.edu/~mryan SAF - Mesa CO May 1, 2009
From SOCCR Report: http://www.climatescience.gov Why does the carbon cycle matter? CO 2 : Warms earth Increases ocean acidity Was lower than 280 ppm for > 400,000 years Rising CO 2 shows sources > sinks CCSP, 2007. The First State of the Carbon Cycle Report (SOCCR): The North American Carbon Budget and Implications for the Global Carbon Cycle .
Global C Cycle <ul><li>Fluxes to and from plants and soil are large </li></ul>Fluxes – how much enters and how much leaves a pool per unit time Pools – how much C is in a given location Petagram = 10 15 g
Forest carbon after disturbance: loss and recovery Photo by Mike Ryan Photo by Dan Kashian Photo by National Park Service Photo by Mike Ryan
How Does Fire Change Forest Carbon? Fire kills trees, it doesn’t consume them; Fire losses of foliage and forest floor are only ~10-20% of the site carbon Photo by Dan Kashian Photo by AZ Dept Emergency Mgmt
Methods <ul><li>Chronosequences replicated across age and tree density (77 independent stands) </li></ul><ul><li>Carbon in: Live and dead wood (above and belowground), soil C (0-30 cm, litter, understory, seedlings and saplings) </li></ul>
Wood Biomass <ul><li>Wood growth is rapid early in life cycle </li></ul><ul><li>Later, growth slows and trees die </li></ul>Wood Biomass Older forests have much higher carbon stores Younger forests have a greater carbon uptake Live Biomass
Dead Wood <ul><li>It is high after a disturbance kills trees </li></ul><ul><li>Lowest when the dead wood from the disturbance has decayed and before large trees start dying </li></ul>Dead Wood Biomass Dead Biomass Time
Forest Floor <ul><li>After a fire, carbon in forest floor (‘duff’ or ‘litter’) increases over 50-60 years then stabilizes. </li></ul>Forest Floor Biomass Usually consumed in fire not consumed in logging or beetle outbreak Forest Floor Time
Mineral Soil <ul><li>Carbon in mineral soil is generally stable, unless large erosion or land-use or vegetation change </li></ul>Soil C Large uncertain pool Measuring change is difficult Soil Carbon Time
The rate of ecosystem carbon storage declines rapidly with time since disturbance Annual Ecosystem Carbon Storage
The carbon lost in the 1988 fire and in the decomposition of the trees killed in the fire will be recovered quickly Total Ecosystem Carbon
What happens with no regeneration? Example: Hayman Fire, Colorado, 2002 Photo by Merrill Kaufmann, USFS
After a fire, if a forest replaces itself, there is little change in C unless Disturbance Interval >> C Recovery Time If fire turns forest into meadow or shrublands, carbon is lost to the atmosphere (for example, Hayman fire, Colorado) Photo by National Park Service
What about MPB Outbreak? Example: Colorado, 1998-? Photo by Merrill Kaufmann, USFS
Large temporary carbon source over a large area
But, the ecosystem C recovers as the trees regrow
The larger the landscape, the more stable the carbon seems
Forest Ecology – Bottom Line <ul><li>Disturbance does not cause C loss, unless forest does not regenerate </li></ul><ul><li>Carbon is best evaluated over large scales of space and time </li></ul><ul><li>The timing isn’t important </li></ul>Photo by Mike Ryan
From SOCCR Report: http://www.climatescience.gov In US, forests and long-lived wood products offset about 12-20% of fossil-fuel emissions North America Mt = (10 12 g) CCSP, 2007. The First State of the Carbon Cycle Report (SOCCR): The North American Carbon Budget and Implications for the Global Carbon Cycle .
US Forest Carbon Balance 1800-1950: Forest Disturbance on a Massive Scale-the Industrial Revolution Birdsey, R., K. Pregitzer, and A. Lucier. 2006. Forest carbon management in the United States: 1600-2100. Journal of Environmental Quality 35:1461-1469. In 1915, emissions from forests were 760 million tons C per year Photo courtesy of University of Washington Libraries, Special Collections, KIN084. ?
In 2000, sequestration by forests was ~200 million tons C per year US Forest Carbon Balance 1950 to 2008: Forest Regrowth on a Massive Scale Birdsey, R., K. Pregitzer, and A. Lucier. 2006. Forest carbon management in the United States: 1600-2100. Journal of Environmental Quality 35:1461-1469. Photo by Mike Ryan
Bottom Line <ul><li>Forests play a large role in offsetting emissions </li></ul><ul><li>Sink may not last </li></ul>Photo by Mike Ryan
The Gorilla in the Room: Tropical Deforestation <ul><li>1-2 Petagrams (10 15 g)/year – about the same as US fossil fuel emissions </li></ul>
Can Forest Management Help? <ul><li>Keeping forests as forests, particularly in the tropics </li></ul><ul><li>Afforestation of previously forested lands – tree planting in the Hayman. </li></ul><ul><li>Forest fuel offsets fossil fuel combustion. </li></ul><ul><li>Forest management – decreasing outputs with longer rotations or less intensive harvest </li></ul>
Take Home <ul><li>We understand forest C cycle at stand level </li></ul><ul><li>If a forest replaces itself after disturbance there is no long-term loss of carbon. </li></ul><ul><li>Time and landscape perspective important </li></ul>NRS Global Change
<ul><li>Ryan, Michael G. 2008. Forests and Carbon Storage. (June 04, 2008). U.S. Department of Agriculture, Forest Service, Climate Change Resource Center. http://www.fs.fed.us/ccrc/topics/carbon.shtml </li></ul><ul><li>Effects of climate change on agriculture, land resources, water resources and biodiversity http://www.climatescience.gov/Library/sap/sap4-3/final-report/default.htm </li></ul><ul><li>State of the Carbon Cycle Report http://cdiac.ornl.gov/SOCCR/ </li></ul><ul><li>Carbon and Yellowstone Fires: http://lamar.colostate.edu/~mryan/Publications/Kashian_Romme_Tinker_Turner_Ryan_2006_Bioscience_56_598-606.pdf and http://lamar.colostate.edu/~mryan/Publications/Final_Report_JFSP_03-1-1-06.pdf </li></ul><ul><li>US Greenhouse Gas Inventory: http://www.epa.gov/climatechange/emissions/usinventoryreport.html </li></ul>Further Reading