Effects of Prescribed Fire on Woody Vegetation in a Gallery Forest Understory in Northeastern Kansas

Woody vegetation in the understory of a gallery forest dominated by large bur oak (Quercus macrocarpa) trees in eastern Kansas was surveyed before (1983) and after two years of annual prescribed burning in April (1984 and 1985). Elm (Ulmus spp.) was the dominant reproduction on the area before burning and increased after burning because of prolific basal sprouting. Five rarer species, including bur oak and chinquapin oak (Q. muehlenbergii), were recorded in 1983 or 1984, but were absent in 1985. Sapling density averaged 1200 per ha prior to burning in 1983 and 0.0 after burning in 1984 and 1985. Total shrub cover significantly decreased from 59.9 percent in 1983 to 9.5 percent in 1985, as a result of decreases in buckbrush (Symphoricarpos orbiculatus) and rough-leaf dogwood (Cornus drummondii). Fire is an important factor influencing the extent of woodlands in the Central Plains of North America. Fire may have been more frequent and intensive during Indian habitation because of their cultural practices (Pyne, 1983) and less intensive grazing of the prairie by bison and elk compared to cattle grazing during European settlement (Bragg and Hulbert, 1976). These factors contributed to the near-complete domination of the Central Plains by grasslands (Gleason, 1913; Sauer, 1950). With decreased fire following European settlement, many grasslands and savannas in the Midwest succeeded to hardwood forests (Kucera, 1960; Penfound, 1962; Abrams, 1986). Despite forest expansion throughout the Midwest, fires recurred in some of these forests (Henderson and Long, 1984; Abrams, 1985a), yet the effects of fire on these communities have rarely been studied (White, 1983; Anderson and Brown, 1983). Many woodland species are destroyed when periodically burned in prairie (Kucera et al., 1963; Anderson and Van Valkenburg, 1977; Adams et al., 1982). Oak (Quercus spp.)-dominated gallery forests on Konza Prairie in eastern Kansas have significantly expanded since European settlement in the midThis content downloaded from 157.55.39.27 on Wed, 07 Sep 2016 05:55:06 UTC All use subject to http://about.jstor.org/terms 64 TRANSACTIONS OF THE KANSAS ACADEMY OF SCIENCE 1800's, despite burning at intervals of approximately 11-20 years or less (Abrams 1985a, 1986). In 1984, annual prescribed burning was initiated in a gallery forest on Konza Prairie in which the woody vegetation had been characterized in 1983 (Abrams, 1986). The purpose of this study is to document fire-induced changes in the composition and dominance ofunderstory woody vegetation in this gallery forest. STUDY AREA AND METHODS This study was conducted on Konza Prairie, a tallgrass (Andropogon, Sorghastrum, Panicum) prairie reserve in northeastern Kansas. Gallery forests in this area are relatively thin bands of woodlands (ranging from about 10 to 300 m wide) that are more or less continuous along stream channels and ravines in the prairie interior. The particular gallery forest studied was approximately 0.8 km in length, 9 ha in area, relatively level (0-4% slope) and dominated by Quercus macrocarpa Michx. (bur oak). It was surveyed in 1983 in an unburned condition and then again in 1984 and 1985 following annual burning in April. Burning occurred just before the leafing-out of most woody species in both years and was included as part of the prairie burning program conducted each spring on Konza Prairie. Prior to 1984, the area had not been burned for at least ten years, but was probably grazed by cattle until 1977. The climate of the study area is continental, characterized by hot summers, cold winters, moderately strong surface winds, relatively low humidities, and frequent summer droughts (Brown and Bark, 1971). The average length of the frost-free season is 180 days and mean annual temperature is 12.80C (monthly range = -2.7 to 26.60C) and mean annual precipitation is 83.5 cm (monthly range = 2.1 to 13.4 cm). Woody vegetation in the gallery forest was surveyed during the middle growing season of 1983-1985. Trees (> 10 cm diameter breast height (1.2 m), dbh) were surveyed once in 1983 using the point-quarter method, in which the closest tree in each of four quadrants was measured (Cottam and Curtis, 1956). Twenty sample points located at 20 m intervals along transects were used in this survey. The transects were oriented through the approximate middle portion of the forest (e.g., the midpoint between the forest edge and stream that bisected the forest). Two arbitrary trees at each point were bored at 1.2 m for age determination. Tree reproduction, including saplings ( 90 percent of the gallery forest area and did not burn the tree crowns. RESULTS AND DISCUSSION The gallery forest overstory was dominated by relatively large diameter, widely spaced bur oak, with chinquapin oak (Q. muehlenbergii Engelm.) as a subdominant (Table 1). The average ages for bur oak and chinquapin oak were 83 and 78 years, respectively. There was a scarcity of small diameter oak trees, which is typical of bur oak-dominated stands on Konza Prairie and in other regions of the Midwest (Cottam, 1949; Abrams, 1985b, 1986). Elm was the dominant reproduction in the gallery forest before and after burning (Table 2). Five rarer species, Kentucky coffee tree (Gymnocladus dioica (L.) K. Koch), bur oak, chinquapin oak, black walnut (Juglans nigra L.) and juniper, Juniperus virginiana L.), were recorded in 1983 and/or 1984 but were absent in 1985. Exact plot locations in 1983 differed from those in 1984 and 1985. Bur oak and chinquapin oak were present in 1984 and absent in 1985 on the permanent plots. The increase in elm (50%) and persistence of hackberry (Celtis occidentalis L.) seedlings following fire resulted from basal sprouting, often producing many stems from a single root stock. Saplings, predominantly elm, averaged 1200 per ha in 1983 and 0.0 in 1984 and 1985. There was no apparent fire-caused mortality to the overstory trees. Dramatic changes in shrub canopy cover occurred following the fires in 1984 and 1985 (Table 3). Total shrub cover significantly decreased (P 10 cm dbh) in a gallery forest on Konza Prairie in eastern Kansas in 1983. Diameter size-class values equal the number of individuals measured in the stand (80 total). Age data Diameter (cm) size-class frequency Species Density (ha-') n R + s.e. 10.0-19.9 20.0-29.9 30.0-39.9 40.0-49.9 50.0-59.9 60.0-69.9 >70.0 Quercus macrocarpa 124 27 83.1 ? 2.9 2 5 10 20 8 17 Quercus muehlenbergii 15 10 78.0 ? 3.9 1 3 6 3 2 Fraxinus pennsylvanica 5 2 19.0 ? 1.4 2 Gleditsia triacanthos 2 1 63.0 1 c0]