Mastication Fuels Did Not Alter Fire Severity or Stand Structure in an Upland Oak Woodland

Abstract

In the eastern deciduous forest region, open oak woodlands once occupied significant areas that are now closed-canopy forests, negatively affecting wildlife habitat and biodiversity. We superimposed midstory mastication and prescribed fire treatments onto sites with ice storm damage, subsequently subjected to sanitation thinning for management restoration. Mastication reduced stem density and basal area, created a variable cover of masticated material, and increased cover of forbs, graminoids, and tree regeneration. Prescribed fire was implemented two years after mastication treatment. We examined fuel changes and whether masticated fuels altered fire severity. Masticated duff depth decreased significantly two years after treatment; no change occurred on nonmasticated treatments. Masticated 1-hour fuels decreased 80% compared to 35% in nonmasticated treatments and masticated 10 h fuels decreased 45% compared to 9.6% in treatments without mastication. Prescribed fire reduced 1, 10, and 100 h fuels on the burn only treatment, and 10 h fuels on the mastication/burn treatment. Burn severity, measured by composite burn index, did not differ between treatments, nor did we measure significant effects of mastication on fire temperature or char height. Fire had no significant effect on stand structure but should be reexamined in three to five years. Repeated burning at three to five y intervals may also be beneficial. Study implications: This study examined the effects of mastication and prescribed fire on upland oak restoration. Findings suggest a single prescribed fire after mastication may not create stand structure reflective of oak woodland restoration priorities. Nonetheless, it will be important to examine fire effects several years later. Additional applications of prescribed fire may be effective in maintaining the stand structure initially achieved through ice storm disturbance, harvest, and mastication. Continued research could gauge the intensity and frequency of prescribed fire treatments needed to retain desired woodland stand structure and develop complex and diverse herbaceous understories characteristic of oak woodlands.