2009

On September 4th and 5th, 2009, fire management staff at Wind Cave National Park completed the 631-acre Headquarters West prescribed fire adjacent to the park’s visitor center. The area burned in a high severity wildfire in 1991, resulting in significant amounts of dead and down fuel as well as prolific ponderosa pine regeneration. Mitigating these two major issues became the focus of prescribed fire managers at Wind Cave as well as the Northern Great Plains (NGP) Fire Management Office, who oversees the fire management programs at Wind Cave, as well as nine other NPS units in South Dakota, North Dakota, Wyoming, Nebraska, and Montana.

Previous fall prescribed fires in NGP parks had also sought to reduce surface fuel loading and pine regeneration, but often ran into difficulty due to constraints on the seasonality of prescribed fire. In the past, prescribed fires had occurred later in the year (late September to early November), rather than during the historic wildfire season in the area (late June-early September). This is due to a number of issues, most notably the increased risk of an escape when burning during the hotter, drier months. This creates a dilemma for managers, who want to meet objectives but also want to manage fire in a responsible manner. That’s where the NGP fire ecology and fire effects program came in. After installing several plots per burn unit for well over ten years, the fire effects crew had the information that park staff needed. The NGP fire effects crew works closely with the managers responsible for writing burn plans at their parks, and the fire ecologist is regularly consulted on developing burn objectives. Usually the summer before a prescribed fire occurs, the fire effects crew installs burn unit-specific plots and then reads them immediately post-burn, as well as for several years thereafter, to determine fire’s effects on the landscape. They also record on-site weather, smoke, and fire behavior data during the burn, so that post-burn assessments can be made regarding weather’s effects on fire intensity and severity.

The NGP fire ecology program presented managers at Wind Cave with data collected on the Hilltop prescribed fire, which occurred at Jewel Cave National Monument (approx. 20 miles northwest of Wind Cave) in the fall of 2008. The Hilltop prescribed fire occurred on October 30th, 2008, and was comprised of much of the same terrain, fuel types, and fuel loading as the Headquarters West unit (Table 1).

Table 1 – Comparison, Hilltop and Headquarters West prescribed fires

It is noteworthy that after achieving only 35% reduction in 1000-hr fuels at Hilltop, managers revised their objectives for Headquarters West, attempting to achieve only a 20% reduction in 1000-hr fuels. In addition to surface fuel objectives, managers also sought to reduce the almost 3,500 ponderosa pine seedlings per acre. After further analysis of both high pre-burn fuel moisture and cooler, humid weather on the day of Hilltop Rx, it was clear that in order to achieve the objectives for Headquarters West, burning would have to occur under drier conditions. After the fire ecology staff provided the fire managers with this information, a burn window at the beginning of September was targeted for Headquarters West. Eventually the unit was ignited on September 3rd, a full seven weeks earlier in the season than Hilltop Rx was burned!

Immediate post-burn data collection and subsequent analysis have shown the objectives to have been successfully met (Figure 1).

Figure 1 – Pre- and post-burn surface fuel loading in Headquarters West prescribed burn unit

The Headquarters West project succeeded in reducing surface fuels by 66% overall, double the reduction seen at Jewel Cave’s Hilltop Rx, and reduced the threat of another high severity wildfire near the park headquarters. Possible explanations for the increased fuel reduction and seedling mortality at Headquarters West include higher temperatures (15-20 degrees higher than Hilltop) and drier fuels (Figure 2), both of which are more likely to occur earlier in the fall prescribed fire season.

Figure 2 – Comparison of fuel moistures, Hilltop and Headquarters West prescribed fires

The Headquarters West prescribed fire was an excellent opportunity for the NGP fire ecology program to directly apply their data to the decision making process. Fire managers were open to input from the fire ecology staff as to how the project as a whole could be more effective and how they might better meet objectives. Fire managers have long known that prescribed fires need to occur during the historic fire “season”, but concerns related to potential escaped prescribed fires can make that difficult. Hopefully this information can provide guidance for managers seeking to rationalize mid-summer to early fall prescribed burning. The NGP fire ecology program learned a lot from this experience and now views their role in prescribed fire planning not just as an opportunity but as an essential part of their job.

Contact: Dan Swanson, Fire Ecologist, NGP Fire Management
Phone: (605) 745-1172

Contact: Andy Thorstenson, Lead Fire Effects Monitor, NGP Fire Management
Phone: (605) 745-1173

Contact: Jon Freeman, Assistant Lead Fire Effects Monitor, NGP Fire Management
Phone: (605) 745-1173

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