Effects of forest structure and prescribed fire on quantity and quality of deer forage

Caleb M. Mckinney, Arjun Adhikari, Ronald E. Masters, Omkar Joshi and Rodney Will, Natural Resource Ecology and Management, Oklahoma State University, Stillwater, OK

Background/Question/Methods
Prescribed fire and thinning can be used to produce and maintain woodlands and savannas which provide improved wildlife habitat and livestock grazing by increasing the productivity of understory vegetation. While the changes in understory composition and productivity with decreasing tree canopy cover are well understood, changes in forage quality are less studied. To understand how forage quantity and quality change among managed ecosystems ranging from closed-canopy shortleaf pine (Pinus echinata) – post oak (Quercus stellata) forest to savanna, we tested the crude protein concentration of 11 species of understory plants. We collected samples at three key times of the year for white-tailed deer (Odocoileus virginianus), early spring when forage quantity is the most limited, mid-summer when deer protein demand is highest, and mid-autumn when forage crude protein is lowest. In addition to protein sampling we measured the annual net primary productivity (ANPP) and tracked monthly changes in understory vegetation cover. This research was conducted at Pushmataha Wildlife Management Area in southeastern Oklahoma where a series of replicated experimental plots established and maintained since 1984 test the effects of four different intervals of prescribed fire and various tree harvesting and thinning regimes.
Results/Conclusions
Understory forage productivity was higher in savanna ecosystems than in forests. Understory vegetation communities shifted throughout the growing season with forbs peaking in coverage before grasses or woody plants. Crude protein concentration was higher in forested areas with longer fire return intervals. Protein concentration also followed predictable annual patterns with high concentrations in the spring and sharp declines in the summer and fall. However, protein concentration of woody plants in forested treatments often decreased at a slower rate than woody plants in savanna ecosystems. White-tailed deer nutritional carrying capacity is a function of both forage quantity and quality, and simply focusing on maximum biomass production may come at the cost of lower quality forage. Managing ecosystems for improving deer habitat should involve interspersed areas of open savannas with high productivity and forests with higher forage quality to meet nutritional constraints throughout the year.