How do you know whether forest fires or factories and diesel generators are responsible for Black Carbon or CO2 in the air or deposited in icefields? An experiment called CARVE (Carbon in Arctic Reservoirs Vulnerability Experiment) led by Chip Miller of the NASA Jet Propulsion Laboratory was conducted in Alaska’s airspace and some results just published explain how the source can be identified. The combustion of woody biomass (or more importantly in Alaska–layers of compacted dead moss and organic soil) liberates primarily carbon deposited since World War II into CO2. That modern post-bomb carbon contains traces of radioactive carbon (Δ14C) in contrast to fossil fuels, deposited in prehistoric times, which have none.
CARVE: Sherpa aircraft flew sensors over fires in Alaska in 2013 to measure atmospheric concentrations of gases.
During the CARVE experiment, Sherpa aircraft flew sensors to measure atmospheric concentrations of CH4, CO2, and CO and parameters that control gas emissions (i.e. soil moisture, freeze/thaw state, surface temperature). They directly flew over some fires (including fires near Fairbanks and Delta) to measure the “fingerprint” concentrations of isotopes released by typical boreal burning. Mouteva et al. (2015) published findings that showed most of the C in the summer skies over Alaska in 2013 was indeed attributable to forest fires and the age of the biomass converted to black carbon averaged about 20 years (range 11-47 yrs). The authors also explore using the carbon isotope “fingerprint” of fires to estimate the average depth of consumption–since Δ14C increases with depth from the surface moss to the mesic horizon. Pooled results of radioactive isotope fractions yielded an average depth of burn of about 8 inches for the 2013 Alaska fires–a result that may vary depending on fuel conditions. Burn severity, expressed as depth of consumption, is a hot topic among agencies and land managers because it drives ecological response to burning as well as vegetation changes which may come with the hypothesized climate-driven increased boreal burning.
Citation: Mouteva, G. O., et al. (2015), Black carbon aerosol dynamics and isotopic composition in Alaska linked with boreal fire emissions and depth of burn in organic soils, Global Biogeochem. Cycles: 29, doi:10.1002/2015GB005247.
Estimates of carbon released from combustion of vegetation and organic soil during wildfires have improved dramatically over the past decade. Biomass inventory, fire effects and fire severity studies have contributed more accurate data to improve these models. (See Ottmar 2007, Brendan Rogers webinar 2015) However, figuring out the net effect of all the various effects of fire, the recovery phase and warming climate on the carbon stored in Alaska’s forests and tundra is a lot more challenging! You’d have to consider changes in burn extent and/or severity, increases in plant productivity in recovering burns, changes in species composition and what that means for productivity, changes in permafrost distribution and soil C decomposition, methane emissions and carbon fluxes in lake systems and wetlands–etc.! A team lead by Dr. Dave McGuire at UAF has taken on this modeling challenge by applying their Integrated Ecosystem Model (IEM) which includes modules for fire, permafrost, and carbon cycling. Dave recently presented an overview of their findings at an IARPC-WCT/AFSC joint webinar (available HERE). In a nutshell, they found: 1) tundra holds 2x the carbon that boreal forest does in the same area 2) there has been a net C loss from boreal land area of about 8 Tg/yr over the last 60 years, primarily driven by large fires during the 2000’s 3) arctic tundra and SE Alaska still act as C sinks, compensating for these losses so that overall, Alaska sequesters about 3.7 Tg/yr, 4) increases in fire extent predicted with with warming climate will release even more C, but longer growing seasons and increased plant growth (as much as 8-19% increased productivity throughout the remainder of this century) with warmer climate and higher CO2 concentration in the atmosphere are estimated to offset these losses under most of the climate projection scenarios. Since this nutshell summary glosses over a lot, you should take a look at the presentation and the SNAP projects page with information on scenarios and the individual models used.
On the surface Alaska fire management and boreal ecosystem carbon studies have little in common. But a deeper look reveals the connections between them. Carbon scientists in the last decade have become increasingly interested in fire effects on the legacy carbon locked up in permafrost and the deep, slow-to-decompose organic layer of boreal forest floor (Kasischke et al. 2013, Genet et al. 2013). Projections indicating more extensive, frequent and/or severe fires in northern latitudes with a rapidly warming climate, longer fire seasons, and more lightning (Romps, et al. 2014) lend a certain urgency to attempts to quantify the potential impacts of fire-released carbon on greenhouse warming. Fire management agencies are less interested in long-term impacts of fire-released gasses but they are more and more driven to assess impacts of smoke on communities. Work at the boundary between the two sets of interests has started to yield some interesting results. For example, Michigan Tech Research Institute has joined their consumption field data from NASA studies to the USFS Consume Model and FCCS fuels maps and LANDFIRE fire perimeters in a web-based tool that provides users a simple interface for computing wildland fire emissions (1-km spatial resolution). The Wildland Fire Emissions Information System (WFEIS) can calculate tons of CO2 or other gases from large fires across the US and Canada from 1984-2010. Although this tool is for post-facto emissions analysis it is a good example of how large spatial data sets and complex equations can be united in a simple graphical interface allowing one to–say–query the forest fire emissions from the 231,000 acres burned in Alaska in 2010 (10.9 million tons CO2, 95,000 tons PM 2.5). The hope is that weather modeling and research linkages with the common fire danger and risk rating system used in northern latitudes (CFFDRS) will soon bring this kind of application into the real-time and forecast prediction realm.
Is Alaska’s Boreal Forest Now Crossing a Major Ecological Threshold?: Read up on what Alaskan forest and climate research has found out about the influence of warming climate on boreal forests in the Interior! Here’s a new 2-page Research Brief that digests one of the more significant papers on forest and climate change. The authors– Dan Mann, Scott Rupp, Mark Olson and Paul Duffy– are well-known to Alaska fire managers. This is a good basis to our upcoming focus on multi-faceted influences of dynamic climate on fire regime, forests, and fire management in Alaska in 2014!
Climate, Fire, Frost and the Carbon Bank: This 2-page research brief summarizes several years of field studies–citing recently published articles–by USGS soil scientists Jennifer Harden and Kristen Manies. Their studies shed new light on the impact of fires on permafrost in Alaska boreal forest, and interactions of fire effects and freezing effects on the forest floor. The insulating moss/duff layer plays a critical role in protecting permafrost and conditions suitable for the rapid regrowth of permafrost are keys to determining whether boreal forest will retain its ability to store large amounts of biomass carbon. Read More >> | Download PDF (1.5 Mb)
Forest thinning, such as this work done in the Umpqua National Forest in Oregon, may be of value for some purposes but will also increase carbon emissions to atmosphere, researchers say. (Photo courtesy of Oregon State University)
John L Campbell, Mark E Harmon, Stephen R Mitchell. Can fuel-reduction treatments really increase forest carbon storage in the western US by reducing future fire emissions?Frontiers in Ecology and the Environment, 2011; : 111215051503003 DOI: 10.1890/110057
Methane Hot Spots, South Central Alaska, January 2010 (Photo by Marie-Laure Geai)
Local scientist Katey M. Walter Anthony (Aquatic Ecosystem Ecologist at UAF) has been studying the amount of methane gas being released into the atmosphere from thawing permafrost. As long frozen plants and other organic materials begin to thaw, they also begin to decay, producing methane gas. Katey has been collecting gas samples from frozen “bubbling” lakes near Fairbanks, Alaska to see just what we’re up against.
Can’t seem to stay up to date? Let us do some of the work.
We’ve put together a bibliography of November’s (plus or minus a few weeks) new fire science publications related to Alaska and the boreal forest. Download a simple bibliography or an annotated version, both in a pdf format including URLs for each reference. Just want the highlights? We showcased a few of our “Top Picks” below.
Werth, Paul A.; Potter, Brian E.; Clements, Craig B.; Finney, Mark A.; Goodrick, Scott L.; Alexander, Martin E.; Cruz, Miguel G.; Forthofer, Jason A.; McAllister, Sara S. 2011. Synthesis of knowledge of extreme fire behavior: volume I for fire managers. Gen. Tech. Rep. PNW-GTR-854. Portland, OR: U.S. Department of Agriculture, Forest Service, Pacific Northwest Research Station. 144 p.
This new article from Science Daily summarizes findings from the first project “to investigate the effect of drainage on carbon accumulation in northern peatlands and the vulnerability of that carbon to burning.”
Four summers ago, Syndonia Bret-Harte stood outside at Toolik Lake, watching a wall of smoke creep toward the research station on Alaska’s North Slope. Soon after, smoke oozed over the cluster of buildings.
The great Anaktuvuk River tundra fire of 2007. Photo by Michelle Mack. (From Alaska Science Forum)