Ecosystem Dynamics and Succession after Tundra Fire, Yukon-Kuskokwim Delta

Gerald Verner Frost, Alaska Biological Research, Inc.--Environmental Research & Services, jfrost@abrinc.com (Presenter)
Lisa B Saperstein, U.S. Fish and Wildlife Service, lisa_saperstein@fws.gov
Rachel A Loehman, U.S. Geological Survey, rloehman@usgs.gov
Kristine Sowl, USFWS Yukon Delta National Wildlife Refuge, kristine_sowl@fws.gov
Matthew J Macander, Alaska Biological Research, Inc.--Environmental Research & Services, mmacander@abrinc.com
Peter R Nelson, University of Maine, peter.nelson@maine.edu
David Paradis, University of Maine, david.p.paradis@maine.edu

The Yukon-Kuskokwim Delta (YKD) encompasses the southernmost, warmest parts of the arctic tundra biome. Ice-rich permafrost currently is widespread and strongly influences terrestrial and aquatic environments. In 2015, the YKD experienced large wildfires across >1,200 km2 of permafrost-affected upland tundra. Although the 2015 fire season was exceptional, tundra fire is common in this region with episodes of historical fire circa 2005, 1985, and 1971, offering a natural laboratory for understanding the ecosystem impacts of tundra fire in a discontinuous permafrost region during a period of warming air and ground temperatures. In 2017, we collected field data on vegetation, soils, and burn severity within recent and historical burns and unburned tundra. Using these data we analyzed patterns of correspondence between vegetation species-composition and structure, soil properties, and fire history. We also tested for differences in biophysical properties among the tundra fire epochs and unburned tundra. Vegetation in unburned tundra was dominated by lichens, whereas burned areas support enhanced cover of shrubs and mosses; however, post-fire shrub cover was composed of the same low-statured species common to unburned tundra and we seldom observed sites colonized by taller, canopy-forming species. Geomorphology and soils were similar in burned and unburned tundra, likely because thick peat layers protected ice-rich permafrost and conferred ecosystem resilience after fire. While this historical perspective suggests that peaty soils will moderate the impact of the 2015 fires, we did observe secondary impacts related to permafrost degradation in circa 2005 fires that were not evident in older burns, such as thaw-settlement, increased surface wetness, complex microtopography, and progressive mortality of shrubs. These contrasts represent persistent, rather than successional shifts and suggest that upland ecosystems of the YKD may be less resilient to wildfire disturbance than they were in the past.

Presentation: ASTM4_Poster_Frost_2_41.pdf (3986k)

Associated Project(s): 

• Frost-01

Poster Location ID: 2

Session Assigned: Wildlife and Ecosystem Services