Wrangell-St. Elias Studies Fires & Permafrost

  Fire In Copper Valley (Journal archive photo, DNR Tazlina)  Repeat fires tip the scale on near-surface permafrost in Wrangell-St. Elias Na...

 

Fire In Copper Valley (Journal archive photo, DNR Tazlina) 

Repeat fires tip the scale on near-surface permafrost in Wrangell-St. Elias National Park and Preserve

From: Wrangell - St Elias National Park & Preserve

October 31st, 2024 


The NPS Alaska Region is exploring opportunities to utilize prescribed fire across specific landscapes to: 1) reduce risk of loss of values (communities, infrastructure, etc.) and 2) maintain ecological processes where the exclusion of naturally occurring wildfire is necessary due to the proximity of values to be protected in the area. However, very little is known regarding the effects of prescribed fire in the Alaska ecosystems as prescribed fire in Alaska is relatively rare and very little intensive monitoring has occurred, particularly in the forested system. To gather the necessary knowledge to effectively and efficiently apply prescribed fire across landscapes fire ecology crews must rely on monitoring the effects of wildfire.

In July of 2024, BIL funds enabled fire ecologists to re-visit a study area an in Wrangell-St. Elias National Park & Preserve that burned twice in rapid series. The 2009 Chakina Fire burned ~ 56,000 acres in the Chitina River Valley. A mere seven years later, a third of the Chakina fire area reburned in the 2016 Steamboat Fire. This frequency of fire return is not typical for Interior Alaska. In fact, the study area has a longer fire-return interval (150 to 200 years) than is typical for most of Interior Alaska (60-150 years). This area also harbors some of the southern-most permafrost, which is typically within a few degrees of thawing and expected to substantially decline in coming decades.


Research Process

The fire ecology crew focused on sampling soil characteristics in:

1) plots that had been unburned for over 100 years; 2) burned once in 2009, and 3) burned in 2009 and 2016.

The crew collected soil for fungal community analysis, measured soil organic mats, thaw depth, and ground surface temperatures. The soil fungal community is essential for nutrient cycling and forming critical symbiotic relationships with vascular plants, which often determine plant growth and survival. While the fungal analysis is ongoing, fire ecologists can share what they observed of the other soil metrics.

They observed that ground surface temperatures increased progressively from the unburned to the once-burned plots, and then increased again to the twice-burned plots. This pattern is closely linked to the thickness of the insulating organic layers.
Specifically, the organic mat depth was, on average, 24 cm thick at the unburned plots, 10 cm at the once-burned, and just 4 cm at the twice-burned plots. In winter, these insulating mats can have the opposite effect, where thicker mats help keep soil warmer. However, this winter effect depends on snow depth, which acts as another insulator.

When probing for active layer depth, the crew hit frozen ground within 1 m of the ground surface in all eight control plots. However, they only detected frozen ground in 54% of the thirteen plots that had burned once, and in just 8% of the twenty-six plots that had burned twice. Near-surface permafrost in this region is expected to significantly decline in the coming decades based on permafrost models and current models of global climate warming (The Fate of Permafrost (U.S. National Park Service) (nps.gov)). These field observations support the models and demonstrate how fires, especially repeated fires, can accelerate the loss of near-surface permafrost in these vulnerable areas.

Next year, fire ecology crews will concentrate on measuring vegetation regeneration in the three treatment areas. They will evaluate forest successional trajectories, as well as the diversity and trait characteristics of returning plant species (did the fire filter out species without fire adapted traits?).

Additionally, they will investigate how postfire root-associated fungi relate to the establishment and growth of boreal tree seedlings. They will compare these findings to other areas of Interior Alaska where fire frequency is higher.

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