Document


Title

Alaskan tundra fires during a time of rapid climate change - Final Report to the Joint Fire Science Program
Document Type: Journal Article
Author(s): Daniel H. Mann; Benjamin V. Gaglioti; Benjamin M. Jones; Eric Miller
Publication Year: 2021

Cataloging Information

Keyword(s):
  • arctic tundra
  • carbon release
  • climate change
  • fire management
  • greenhouse gas
  • post-fire vegetation
  • tundra fire
Region(s):
JFSP Project Number(s):
16-1-01-8
Record Maintained By:
Record Last Modified: December 16, 2021
FRAMES Record Number: 64977

Description

This project concerned tundra fires in Alaska and how climate-driven changes in fire regimes could impact Alaska’s Arctic ecosystems. We used remote sensing, dendrochronology, field vegetation surveys, and paleoclimate reconstructions to accomplish three goals: 1) to identify the extent and timing of past tundra fires occurring in Arctic Alaska, 2) to document the effects of these fires on vegetation and permafrost, and 3) to determine how these effects might change in a warming, more variable climate. The main study area for this work was the Noatak River in Northwest Alaska, which has been one of the most fire-rich regions of the Arctic in recent decades, and which provides a useful analog for a more flammable tundra biome in the future. We found that, in addition to the already-identified constraints imposed by summer climate, Arctic tundra fires are limited regionally by ignition sources, and more locally by the type and amount of fuels available on the landscape. Over the last 50 years, 97% of the area burned was in two fuel types: tussock tundra and erect shrub tundra. Based on remote sensing data and on-the-ground observations, tundra vegetation typically recovers to pre-fire greenness values within three years after a fire. Tundra fires resulted in two phases of increased primary productivity as manifested by increased landscape greening relative to pre-fire normals. Phase One occurred in most burned areas 3–10 years after a fire, while Phase Two occurred 16–44 years after fires at sites where burning triggered near-surface permafrost thaw that led to the proliferation of erect shrubs. Satellite-derived vegetation productivity indices suggest that on a multi-decadal time scale (from 10 years before fires to 44 years afterwards), tundra fires act to enhance the cumulative primary productivity by ∼7% and thus may act as a net greening agent. This fire-induced greening may act to partially offset a fire's climate-warming effects through greenhouse gas emissions and surface albedo changes following tundra fires, especially in cases where carbon-rich permafrost is not being thawed and ancient carbon is absent or evades combustion. A positive feedback in which fires lead to shrubification that leads to greening and more fires is currently operating in the Noatak valley, and this feedback could expand northward as air temperatures, fire frequencies, and permafrost degradation increase. However, this feedback will not occur at all locations. In the Noatak valley, the fire-shrub-greening feedback occurs infrequently in tussock tundra communities where low-severity fires and shallow active layers exclude shrub proliferation. Climate warming and enhanced fire occurrence will likely shift fire-poor landscapes into either the tussock tundra or erect-shrub-tundra ecological attractor states that now dominate the Noatak valley. In addition to these findings, we also developed new methodologies, including a ‘flammability index’ for tundra vegetation types, and a new method for analyzing the satellite-based Enhanced Vegetation Index that focuses on the effects of fire and removes any ongoing effects of warming observed in unburned areas.    

Online Link(s):
Link to this document (1.4 MB; pdf)
Citation:
Mann, Daniel H.; Gaglioti, Benjamin V.; Jones, Benjamin M.; Miller, Eric. 2021. Alaskan tundra fires during a time of rapid climate change - Final Report to the Joint Fire Science Program. JFSP Project No. 16-1-01-8. University of Alaska-Fairbanks. 33 p.

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