A plant ecological perspective on prescribed fire for wildlife management in oak/hickory woodlands: Consequences for leaf production, oak regeneration, and heterogeneity in light in the understory

Background/Question/Methods

Fire is used to manage for wildlife in many oak/hickory woodlands. Regeneration of oak woodlands in “degraded” (closed) forest/woodland is a management goal with the hope of increasing plant diversity. However, connecting how prescribed fire is affecting ecosystem processes and function is limited, and generally not related back to management by fire. Here I link the relationship between total light availability and heterogeneity in light availability to overstory leaf production, oak regeneration and plant diversity. I also address how overstory leaf production is related to ecosystem processes. Finally, I address how prescribed fire is “preserving” and “sustaining” the oak/hickory ecosystem. I monitored plant overstory production for twelve years in oak/hickory woodlands in various stages of management (unburned, burned since 1999, burned since 1980). In addition, measurements of light, ecosystem function (decomposition rates, soil respiration rates, herbivory, gas exchange), temperature and rainfall patterns, and plant diversity (over, mid- and understory) were obtained over various time and spatial scales. I used eighteen circular 0.1ha plots established across three “treatments/habitats” at the Drury-Mincy Conservation Area in Taney County, MO to collect data. In addition, belt transects and 100 m² areas were sampled.

Results/Conclusions

Prescribed fires clearly result in canopy opening and greater photosynthetically active radiation reaching the understory. In addition, canopy closure across all woodland burning histories (as measured by a densitometer) in this study was related to light transmittance to the understory by the following equation: y= 0.999 - 0.810Tau (r² = 76.5). Opening the canopy is obviously a driver in plant community structure. For example, principal component analysis indicates that most of the variability between habitats with different fire histories is due to understory species richness, canopy closure, and basal area of overstory trees. However, heterogeneity in light is not statistically related to patterns in diversity or ecosystem processes. Nonetheless, spatial analysis of light vertically and horizontally indicates that light availability becomes more heterogenous when burning is first initiated and then becomes similar to unburned sites as burning is prescribed over a 20 year period. In these oak/hickory woodlands, recently burned areas do not have significant oak regeneration, and plant community structure and function is still more typical of a closed forest than open woodland. The use of selective thinning, manual gap formation, and growing season burns is needed if the goal of management is to promote plant diversity, oak regeneration, and diverse habitat for wildlife.