This RAPID project takes advantage of a wildfire from the summer of 2012 to study the impacts of multiple disturbances on the functioning of pine forests in the Rocky Mountain region. The High Park Fire was the largest and most damaging in Colorado history, although fires of its magnitude are expected to become more common throughout the region in a warmer future. In this case, the range of disturbance histories within the perimeter of the fire area provides a rare opportunity to study the impact of pre-fire disturbance history on forest carbon and nutrient cycling. The investigators will make measurements of the amounts and distribution of remaining living and dead organic matter and chemicals in vegetation, on the ground and in the soil in burned and unburned forest patches, while also noting whether or not the patches had been previously infested by mountain pine beetles. This will enable tests of the additive impacts of insect outbreaks and wildfire and enable more informed predictions about potential forest conditions in the future in this region. Instruments will be installed by university scientists in plots burned in the fire that were also either infested or not by beetles during the most recent outbreak and compared with unburned plots. The U.S. Forest Service will measure trees, ground cover and soil conditions on the ground in the plots that can be resampled and compared to measurements made in the future. New analytical techniques will be applied to characterize soil organic matter composition and age. Finally, a newly available aircraft from the National Ecological Observatory Network equipped with hyperspectral and LIDAR sensors will be flown to provide blanket coverage of immediate post-fire surface conditions in the entire fire area so that results can be extrapolated from plot measurements.
This project involves a novel collaboration of multiple universities in Colorado and Arizona, NEON, and the U.S. Forest Service that will provide valuable information to forest managers as they contemplate a future with more fire, as well as unique scientific insights into how history affects the responses of forest ecosystems to multiple stressors.
In the last decade we have seen fires and insects devastate the forests in the Western USA. Millions of hectares of trees from New Mexico to Canada have been burned, chewed up by insect outbreaks or have experienced both threats. The combination of these disturbances alter the soil in forests; they change the way that forests regenerate and change the way that forests hold onto nutrients needed for healthy forest growth and the provision of sustained forest services like recreation, habitat for game, lumber and storing carbon from the atmosphere. In this study we examined how soils changed after they were burned in the 2012 High Park Fire. Some of the forest we studied had been previously killed by Mountain Pine Beetle. We found that soils became less acidic after they were burned. This in turn changed how soil microbes were able to regenerate nutrients in the soil. When mountain pine beetles kill trees, needles accumulate on the ground and trap more moisture in the soil. However when the forest burns the needle layer is destroyed and if the fire is severe enough, it is as if the beetles had never been a part of the story. This research has broader implications also. Nutrients in soils are very dependent on the microbes that live there. This research has found that soil microbes are sensitive to the intensity of forest fire and that this sensitivity might improve our ability to predict how forests will work after forest fires and beetle outbreaks.
