HR: 16:15h
AN: B14C-02 INVITED    [Abstracts]
TI: Landscape and climate controls on fire severity in Alaskan black spruce forests
AU: * Kasischke, E S
EM: ekasisch@umd.edu
AF: University of Maryland, Department of Geography, College Park, MD 20742, United States
AU: Turetsky, M R
EM: mrt@msu.edu
AF: Michigan State University, Departments of Biology and Fisheries and Wildlife, East Lansing, MI 48824, United States
AU: Kane, E S
EM: ftesik@uaf.edu
AF: Michigan State University, Departments of Biology and Fisheries and Wildlife, East Lansing, MI 48824, United States
AU: Treat, C
EM: treatc@msu.edu
AF: Michigan State University, Departments of Biology and Fisheries and Wildlife, East Lansing, MI 48824, United States
AU: Harden, J W
EM: jharden@usgs.gov
AF: U.S. Geological Survey, 345 Middlefield Road, Menlo Park, CA 94025, United States
AU: Manies, K
EM: kmanies@usgs.gov
AF: U.S. Geological Survey, 345 Middlefield Road, Menlo Park, CA 94025, United States
AU: Ottmar, R D
EM: rottmar@fs.fed.us
AF: U.S. Forest Service, Pacific Wildland Fire Sciences Laboratory, Seattle, WA 98103, United States
AU: McGuire, A D
EM: ffadm@uaf.edu
AF: University of Alaska, Department of Biology and Wildlife, Fairbanks, AK 99775,
AU: Yi, S
EM: ffsy@uaf.edu
AF: University of Alaska, Department of Biology and Wildlife, Fairbanks, AK 99775,
AB: Black spruce (Picea mariana) forests are the dominant forest cover found in the Interior (boreal) region of Alaska and throughout most of Canada, with most of the forests established through secondary succession following fires. These forests have deep surface organic layers (10 to > 40 cm thick) and are frequently underlain by permafrost. An important measure of fire severity in these forests is the depth of burning of the surface organic layer. Variations in this depth of burning controls many post-fire ecosystem characteristics and processes, including ground temperature and moisture, permafrost dynamics, seasonal rates of soil thawing, vegetative reproduction, and seedling establishment and growth. Over the past several years, several different research groups have focused on collecting data on the depth of the surface organic layers in burned and unburned black spruce forests in Interior Alaska. Combined, these data were collected in some 800 burned and unburned stands associated with 37 fire events that occurred between 1983 and 2006. The data set consists of over 18,000 individual organic layer depth measurements, nearly equally divided between burned and unburned stands. Our analyses of this data set show that variations in the depths of both unburned and burned organic layers is strongly controlled by the topographic position of the black spruce forests, with deeper organic layers being found on flat sites compared to sites on slopes, and deeper organic layers being found on north-facing slopes compared to south-facing slopes. In addition, we found that sites that burned later in the growing season (after July 20) had shallower organic layers compared to sites that burned early in the growing season (prior to 20 July). This difference is attributed to the effects that seasonal thawing of the ground layer (in sites with permafrost) has on site drainage. Finally, sites that burned during the ultra-large fire years of 2005 and 2006 (where greater than 3 percent of the total land surface burned during each year) had shallower organic layers than sites that burned during small fire years (where less than one percent of the land surface burned during a year). We attribute this difference to the overall drought conditions that occurred during the ultra-large fire years, which led to lower duff moisture and deeper burning fires. These results show that critical differences in fire severity in black spruce forests are linked to climate driven-variations in the fire regime, specifically the frequency of large fire years at a regional scale and the seasonality of burning.
DE: 0400 BIOGEOSCIENCES
DE: 0414 Biogeochemical cycles, processes, and modeling (0412, 0793, 1615, 4805, 4912)
DE: 0426 Biosphere/atmosphere interactions (0315)
DE: 0428 Carbon cycling (4806)
DE: 0434 Data sets
SC: Biogeosciences [B]
MN: 2007 Fall Meeting