UW Bulletin Details Post

A new University of Wyoming bulletin will aid researchers, land managers and others in understanding some of the underlying mechanisms of ponderosa pine ecosystem recovery following high-intensity wildfires.

The publication details a study examining ecological impacts of the 2012 Arapaho Fire, which burned nearly 100,000 acres in the north Laramie Mountains of southeast Wyoming, including the UW-owned Rogers Research Site (RRS).

Preliminary results indicate the addition of soil amendments to a burned site, including compost and its aerated teas, could improve short-term recovery rates of the microbial community and soil nutrients, among the key elements for plant growth.

The findings are presented in RRS Bulletin 8, “Soil amendment addition and microbial community recovery following high-severity fire, Rogers Research Site, north Laramie Mountains, Wyoming.”

“Fire can have significant impacts on forest ecosystems, most visible of which are the above-ground effects on vegetation, but below-ground effects may be even more important to study,” says co-author Linda van Diepen, an assistant professor of soil microbial ecology in the UW Department of Ecosystem Science and Management within the College of Agriculture and Natural Resources.

“More specifically, the soil microbial community plays an important role in nutrient provision to the vegetation and, thus, it is important to know how restoration efforts may help in the recovery of the microbial community,” she adds.

In spring 2012, UW graduate student Claire Wilkin and her faculty co-adviser, Professor Steve Williams, established eight monitoring plots at RRS to document soils, plant distribution, water sources, topographic features and below-ground biota.

Coincidentally, they had collected soil samples within the plots just weeks prior to the lightning-caused Arapaho Fire, which started during an extreme drought and killed the majority of ponderosa pine within the 98,000-acre burn area. With this baseline information in hand, Wilkin and Williams refocused their study on pre- and post-fire soil comparisons, which are detailed in RRS Bulletin 7, a companion publication released in December.

After observing noticeable changes in soil chemical and biotic changes, Williams and Wilkin became interested in exploring the subsequent effect these changes might have on the soil microbial communities, which are detailed in RRS Bulletin 8.

The focus was to investigate the effectiveness of soil amendments for re-establishing the soil microbial community and hastening recovery of the site to a healthy successional environment following the high-severity fire.

The amendments included nitrogen fertilizer in the form ammonium nitrate (NH4NO3), traditional compost and compost tea, a liquid produced by extracting plant growth compounds and beneficial microorganisms from compost steeped in water.

The other treatments included a water-only control and a blank control with no additions.

Four sample sets were collected: one day prior to the Nov. 13, 2012 treatments, and approximately one week, six months and nine months post-treatment.

Most of the amendments stimulated microbial populations to higher levels compared to the no-addition control, though it was often short-lived and not significant. The addition of organic amendments in the form of compost and its aerated teas may have stimulated ammonification and fungal activity, in addition to narrowing fungi:bacteria ratios over the short term.

“Soil amendments, as applied in this study, can have some short-term positive effects on the soil microbial community, which is often severely negatively impacted by fire,” van Diepen says. “Further studies, however, would be needed to understand the long-term effects of amendments on soil microbes and how this feeds back to vegetation establishment.”

Since Wilkin’s graduation and Williams’ retirement, a team of UW faculty and students led by van Diepen has continued soil biogeochemical measurements and related above-ground studies at RRS.

Ongoing and future research at RRS will provide additional information on the recovery of the soil microbial community, as well as nutrient conditions over the long term after the wildfire with additional restoration treatments, van Diepen says.

These additional treatments are focused on the long-term restoration of ponderosa pine at RRS and surrounding lands in the Laramie Mountains. Preliminary results of the ponderosa study are detailed in RRS Bulletin 5.

The first eight bulletins detailing research, extension, teaching and other activities at RRS are posted at http://bit.ly/RogersResearchSite.