The Effects of Prescribed Burning on Oak Woods and Prairies in the Indiana Dunes.
From: Cole, K. L., P. Benjamin, and K. Klick. 1990. The effects of prescribed burning on oak
woods and prairies in the Indiana Dunes. Restoration and Management Notes 8:37-38.
A study was initiated by Indiana Dunes National Lakeshore to investigate the vegetation
changes resulting from prescribed burning at Howes Prairie: A complex of oak savanna and
prairie communities within the Indiana Dunes. The area was stratified into four major
community types; wet prairie, mesic prairie, oak woods, and mesic woods, and random study
plots were used to measure tree density, tree basal area, sprout density, shrub cover,
shrub density, herbaceous frequency, and fire intensity. Three treatment areas; control
(no burn), high frequency burn, and low frequency burn, were established in 1983 and first
burned in the spring of 1986. A fall burn treatment was established and burned in 1989.
Measures of fire intensity during burns using temperature sensitive paints on aluminum tags and mica sheets demonstrated that each community type produced a characteristic profile of temperature above and below ground level. However, significant between-plot variability in fire intensity also occurred within each community type. In general, wet and mesic prairie produced high above-ground temperatures and low below-ground temperatures. Conversely, oak woods and mesic woods produced relatively low above-ground temperatures and relatively high below-ground temperatures.
Tree basal area was reduced on the burn areas as a result of top-killing of trees. The percent of trees killed was correlated to fire intensity and tree DBH. Mesophytic tree species such as red maple, cherry, and dogwood were greatly reduced by the burn treatments. However, sprout production by top-killed black oaks, sassafras, and aspen was enhanced, greatly increasing shrub cover of these species and potential future tree basal area in the absence of future periodic burning. On the first burn, 45% and 53% of the trees were top-killed on the two burn treatments. However, total mortality of trees (both shoots and roots killed) was low compared to top-killing of trees. Areas with two and three burns during a four year period averaged 3.71% and 3.65% total mortality of black oaks per year. These numbers can be compared to 2.1% mortality per year over the unburned control area during the same period.
Shrub and herbaceous species cover was low on all treatments during 1988 as a result of a drought-induced low water table, but some longer term trends were also evident. Coverage of willow increased markedly on the burn treatments while remaining even on the control. Shrub coverage of aspen sprouts and raspberry increased on all treatments, with aspen showing the steepest rise in response to burning and raspberry increasing most on the control.
The average number of herbaceous species within 1/2 m2 quadrats increased on the burn areas, especially in the wooded communities on the high frequency burn treatment. However, the high between-plot variability in these measurements taken from 600 quadrats, requires that sampling continue in the future in order to validate the statistical significance of these trends. Like species number, frequency of herbaceous species generally increased on the burn treatments but was influenced by the community type and fire intensity.
This data set, including three years of pre-burn sampling and a control treatment, allows the discrimination of many vegetational trends both correlated to, and independent of, the fire treatments. While most changes noted during the sampling period were correlated with fire, other changes appear to be more related to yearly moisture levels and/or successional trends.