Understory vegetation response in longleaf pine forests to fire and fire surrogate treatments for wildfire hazard reduction and ecological restoration
Abstract
The principal objective is to quantify the responses of the understory plant community to fire and fire surrogate treatments, specifically plant species composition, foliar cover, species richness, diversity, and evenness changes resulting from (1) fire exclusion in the untreated control, (2) prescribed fire, (3) thinning, (4) thinning plus prescribed fire, and (5) herbicide plus prescribed fire. The study should identify the individual species and groups of plants that are most affected (both positively and negatively) by the experimental treatments. The most effective treatments for mitigating the wildfire hazard and restoring the natural structure and function of longleaf pine forests appear to be the thinning+fire treatments. Both are very effective in rapidly establishing the appropriate stand architecture that then facilitates the safe application of periodic surface fires to achieve and maintain overall forest health. Application of these two treatments also enhances habitat quality by promoting the re-establishment and expansion of native grasses and forbs in the understory plant community. The only noteworthy disadvantage of the herbicide+fire treatment is the decline in understory plants during the period immediately following herbicide application. Fortunately, these resilient ecosystems rapidly recover from this transitory impact. Although the fire treatment is also of some value, it produces results that appear to be less consistently beneficial across the full range of plant groups. While thinning was thought to perhaps serve as a surrogate for prescribed fire, it is now recognized that its effects and benefits are ephemeral and easily lost once woody vegetation regrows to occupy an even greater proportion of the site. Thus, thinning that is not rapidly followed up (in perhaps no more than one year) with prescribed fire is of little value in mitigating wildfire danger or contributing to the aims of ecological restoration.