Physical short‐term changes after a tussock tundra fire, Seward Peninsula, Alaska

Abstract

The Kougarok area, situated on the central Seward Peninsula, Alaska, experienced a severe fire in August 2002. This may be the only tundra fire where high‐quality prefire (1999–2002) and postfire (2003–2006) active layer and meteorology measurements have been collected in the same locations. After fire, near‐surface soil showed increased moisture at the burned tussock site, remaining close to saturation throughout the thawed season 2003–2006. Despite wetter soil after the fire, freezing occurred earlier at the burned tussock site than at the control, indicating the importance of a reduced organic layer. Severe combustion of lichen and moss left 15–25 cm high tussocks, resulting in a doubling of the surface roughness coefficient. Average September temperature at the tussock site increased 2.3 ± 0.7°C throughout the 1 m soil profile, doubling the active layer depth, although this is due partly to favorable meteorological conditions. The shrubby control station experienced a mean annual temperature increase of 1.1 ± 0.3°C in the upper 0.5 m. A similar annual change was found at the burned tussock site. Cooler weather conditions in 2006 stagnated the soil‐warming trend, which occurred after 2002. How the thermal and moisture regimes in tundra will be affected after fire is highly influenced by weather, fire severity, vegetation regrowth, prefire vegetation, and ground ice conditions.

The response of Arctic vegetation and soils following an unusually severe tundra fire

“…Over the next century, climate warming will likely interact with fire to accelerate permafrost thaw. Owing to changes in surface energy balance, the depth of the active layer is commonly increased in the first few years following fire in tundra ecosystems [10,13,40,47,56]. After fire, the depth of the active layer in burned sites may be deeper than in unburned sites for two or three decades [14,15,40], though in other cases it returns to unburned levels within about 10 years [13].…”

Vegetation mediated the impacts of postglacial climate change on fire regimes in the south‐central Brooks Range, Alaska

“…Thus, the future expansion of tundra shrubs (Tape et al 2006, Walker et al 2006) coupled with decreased effective moisture (ACIA 2004) could enhance circumarctic burning and initiate important feedbacks with the climate system. Recent studies of modern tundra fires suggest the possibility for both short-and long-term impacts of increased tundra burning ranging from increased summer soil temperatures and moisture levels (Liljedahl et al 2007) to the release ancient soil carbon from increased permafrost thawing and organic-layer consumption , Liljedahl et al 2007). Given the concern over the fate of terrestrial carbon in tundra and other high-latitude ecosystems (Zimov et al 1999, Mack et al 2004, Weintraub and Schimel 2005, the evidence of fires in early Holocene tundra should motivate research into the controls of tundra fire regimes and links between tundra burning and the climate system.…”

Interactions between soil thermal and hydrological dynamics in the response of Alaska ecosystems to fire disturbance

“…Data from seven sites in Alaska were used to evaluate the EnvM in this study (Table 1): a tussock ( Eriophorum vaginatum ) tundra site located at Kougarok (K2) on the Seward Peninsula; a poorly drained black spruce ( Picea mariana ) site (FBKS) located near Fairbanks, Alaska; and two black spruce fire chronosequences located in Donnelly Flats near Delta Junction, Alaska (DFTC, DFT87, and DFT99; DFCC and DFC99), which represent well drained (DFTC, DFT87, and DFT99 sites) and intermediately drained (DFCC and DFC99 sites) conditions. The K2 site, which is located in an area of transition between continuous and discontinuous permafrost, experienced a severe to moderate burn in 2002, which removed 7–9 cm of organic soil between the Eriophorum vaginatum tussocks [ Liljedahl et al , 2007]. The K2 site is unique in that it has soil temperature and moisture measurements obtained from the same location both before and after the fire [ Liljedahl et al , 2007].…”

“…The K2 site, which is located in an area of transition between continuous and discontinuous permafrost, experienced a severe to moderate burn in 2002, which removed 7–9 cm of organic soil between the Eriophorum vaginatum tussocks [ Liljedahl et al , 2007]. The K2 site is unique in that it has soil temperature and moisture measurements obtained from the same location both before and after the fire [ Liljedahl et al , 2007].…”