A paper just published by the indefatigable Adam Young, a PhD candidate at the University of Idaho, and colleagues pulls together a lot of information about climate, forest, tundra and fire to offer a glimpse of potential future fire regimes in different parts of Alaska. By looking at fire occurrence at a multi-decadal time scale, the researchers drill down into how fire rotations are likely to respond to climate projections at a regional scale.
Exerpt from Fig. 6, Young et al. 2016. Figures in the paper not only show the observed fire rotation for 19 subregions of Alaska (Figure A2 in supplement) with 60 years of fire occurrence data, but also project future rotations under various climate scenarios (in this case a mean of of 5 global climate models).
The use of advanced statistical models to build fire-landscape response models for boreal forest and tundra reaffirms prior findings of the sensitivity of fire regime to summer temperatures and moisture deficit. However, the effect is not uniform among regions: they identify a threshold at about 56⁰ F (30-yr mean temperature of the warmest month) and another threshold for annual precipitation where fire occurrence really seems to jump. This latter finding accounts for results which project large increases in 30-year probability of burning for areas where these thresholds will be crossed in the next several decades. For example, models project the Brooks Range foothills of the North Slope, Noatak tundra and the Y-K Delta may see increases in fire 4-20x greater than historical levels. Some tundra areas are likely to experience fire frequency increase to levels not observed in the paleo record, spanning the past 6,000-35,000 years. Across most of the boreal forest, fire rotation periods are projected to be less than 100 years by end of the 21st century. This is useful information for natural resources management as well as fire protection agencies—a concise, well-researched, well-illustrated paper—put it on your summer reading list.
Young, A. M., Higuera, P. E., Duffy, P. A. and Hu, F. S. (2016), Climatic thresholds shape northern high-latitude fire regimes and imply vulnerability to future climate change. Ecography 39: 1-12. http://dx.doi.org/10.1111/ecog.02205
It has long been assumed that bark beetle outbreaks on the Kenai lead to increased fire danger, even though beetle disturbance has been shown to have mixed effects on crown fire potential, fuel profiles and burn severity in the Rocky Mountains. Winslow Hansen, doctoral candidate at the University of Wisconsin, recently published an analysis of beetle outbreaks and fire on the Kenai Peninsula between 2001-2014 (Hansen et al. 2016). He looked at effects in pure white spruce stands–where duration of beetle attacks is longer and mortality greater–and in mixed white and black spruce stands common on the northern peninsula, where attacks are less severe. His analysis indicates mixed effects: severely damaged white spruce stands did not demonstrate increased fire occurrence (instead, % canopy cover appeared to drive likelihood of burning) while the mixed white/black spruce stands didshow a positive correlation with beetle outbreaks and fire. Winslow explores the reasons for this in his relatively short article: worth reading. You may remember Winslow from his previous work on beetles/fire effects and property values on the Kenai (recorded MS Thesis defense) and climate effects on fire regime (recorded 2015 presentation).
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.
Fig. 1. Yearly and monthly number of lightning flashes in Alaska from 1986-2010 (Farukh and Hayasaka, 2012)
A recent article in Science magazine (Romps, et al. 2014) postulated a 12% increase in lightning strikes over the continental US for each degree C of warming. If this model holds true for Alaska, we should have already seen an increase in lightning strikes of roughly 20% in interior Alaska over the last 25 years since summer temperature has warmed by about 2.5 F–up to 3.7 F north of the Brooks Range (data from UAF Geophysical Institute). So, has anyone looked at the trends in Alaska’s Automatic Lightning Detection Data to see what has been observed? AFS has been collecting this data (publicly available at http://fire.ak.blm.gov) since 1986. It turns out the answer is yes! Drs.Farukh and Hayasaka (2012) published an article on how large lightning storms characterized some of our largest recent fire seasons including this figure. I’d like to challenge other investigators to look at the regional significance of this phenomenon in the state, which could be an important fire regime driver in boreal forest/tundra, with the data which is now complete (ALDS went offline in 2013, replaced by a time-of-arrival system)!
This presentation and MANY MORE available on fuel moisture sampling, remote sensing validation of FWI, new remote sensing tools for fire detection and growth modeling, using dataloggers on soil moisture probes to track fuel moisture changes, and the seasonality of CFFDRS, to name a few.
Fire Severity Filters Regeneration Traits to Shape Community Assembly in Alaska’s Boreal Forest: A recent paper by Hollingsworth et al. (2013) proposes that fire severity and a plant’s intrinsic regeneration strategy are key determinants in post-fire community recovery. The authors identify species that may fare better or worse with predicted changes in Alaska’s fire regime. Hollingsworth–who is based at the University of Alaska-Fairbanks–bases her findings on a large (n = 87) and geographically diverse set of post-fire plots in interior Alaska boreal forest.
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!
Global wildland fire season severity in the 21st century: A 1-page research brief summarizes a recently published article by Canadian fire scientist Mike Flannigan of the University of Alberta. Dr. Flannigan is well-known in Alaska fire management circles due to his contributions to boreal forest wildfire studies and the Canadian large fire database. This 2013 article describes the use of component indices of the Canadian Fuels Danger Rating System to forecast future changes in fire season severity world-wide.
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)