Poster Session II
Project Type
Poster
Project Funding and Affiliations
Montana Space Grant Consortium, USDA Fire Science Laboratory, UM Department of Conservation and Ecosystem Science, UM Division of Biological Sciences
Faculty Mentor’s Full Name
Justin Gay
Faculty Mentor’s Department
Department of Ecosystem and Conservation Sciences
Abstract / Artist's Statement
Wildfires in western United States conifer forests have increased in both frequency and severity due to human-caused climate change, with important but poorly constrained implications for carbon (C) cycling in these ecosystems. The largest pool of ecosystem C in forests is belowground, though much of it is insulated against direct combustion from fire. Therefore, understanding how changing wildfire regimes influence ecosystem C requires not only quantifying soil C pools to capture direct effects but also evaluate the indirect and legacy effects of fire on C cycling, including changes in microbial C processing.
To evaluate the direct and indirect fire effects, we collected mineral soil samples and intact soil cores from both burned and unburned plots across a gradient of fire return intervals (FRI) 14, 23, and >100 years between fires, and time since last fire (TSF) of three and 15 years in western Montana subalpine lodgepole forests. In a coupled lab experiment, we examined soil microbial respiration after wetting. All soils displayed similarly low background carbon dioxide (CO₂) flux prior to rewetting; however, rewetting revealed a strong TSF response, with microbial respiration 2.6 times lower three years after fire compared to 15. In contrast, mineral soil C were unaffected by TSF, but declined under shortened FRI. Unburned plots had 68% more C in the top 10 cm of mineral soil than the short FRI. Together, these results indicate that fire recency suppress short term microbial processing of C, whereas repeated burning reduces soil C storage over longer timescales.
Category
Life Sciences
Recency vs. Frequency: Contrasting Controls on Soil Carbon Cycling After Wildfire in Subalpine Lodgepole Pine Forests
UC South Ballroom
Wildfires in western United States conifer forests have increased in both frequency and severity due to human-caused climate change, with important but poorly constrained implications for carbon (C) cycling in these ecosystems. The largest pool of ecosystem C in forests is belowground, though much of it is insulated against direct combustion from fire. Therefore, understanding how changing wildfire regimes influence ecosystem C requires not only quantifying soil C pools to capture direct effects but also evaluate the indirect and legacy effects of fire on C cycling, including changes in microbial C processing.
To evaluate the direct and indirect fire effects, we collected mineral soil samples and intact soil cores from both burned and unburned plots across a gradient of fire return intervals (FRI) 14, 23, and >100 years between fires, and time since last fire (TSF) of three and 15 years in western Montana subalpine lodgepole forests. In a coupled lab experiment, we examined soil microbial respiration after wetting. All soils displayed similarly low background carbon dioxide (CO₂) flux prior to rewetting; however, rewetting revealed a strong TSF response, with microbial respiration 2.6 times lower three years after fire compared to 15. In contrast, mineral soil C were unaffected by TSF, but declined under shortened FRI. Unburned plots had 68% more C in the top 10 cm of mineral soil than the short FRI. Together, these results indicate that fire recency suppress short term microbial processing of C, whereas repeated burning reduces soil C storage over longer timescales.