Use of comparison areas rather than controls in a study of fuels in invaded forests of the northeast and mid-Atlantic states

Abstract

In paired studies where the comparison is between a treated and untreated forest area, the unrnanipulated stand is often called a control. The two areas might not be consistent in forest cover type, understory plant communities, disturbance history, soils, slope, and aspect. To enhance rigor in forest research, the reference stand should receive more scrutiny and, unless it matches the treated area well, can be regarded as a comparison area rather than a control. For example, in a new study of interactions between fire and invasive plants, we sought paired areas - one that was heavily invaded by exotic plants, and a nearby or contiguous uninvaded area. Among our 13 pairs at 12 sites, we found a few stands that were completely fiee of exotic plants, but most of our comparison areas were compromised by one or more small, patchy populations of invasive species. This might not matter, as we found significant differences between invaded and uninvaded conditions, especially in fine fuels. Invasive plants alter the fuel bed in pitch pine stands where invasion by black locust leads to substantial reduction in fine fuels. Fire return interval and fire intensity are expected to decrease in such situations. Where invasive grasses such as Japanese stiltgrass or wood blue-grass are present, grass fuels are much more abundant in invaded forests. This could lead to rapid spread of wildfire in a dry year. Though we lacked ideal controls, the mostly uninvaded comparison areas provided an opportunity to understand how fuel loads differ when invasive plants are present.

Citation

Dibble, Alison C. 2004. Use of comparison areas rather than controls in a study of fuels in invaded forests of the northeast and mid-Atlantic states. In: Proceedings, Society of American Foresters 2003 national convention; 2003 October 25-29; Buffalo, NY. Bethesda, MD: Society of American Foresters: 319-324.