Fire History and Stand Structure of High Quality Black Oak ( Quercus velutina ) Sand Savannas (original) (raw)
Related papers
Prescribed Fire in Oak Savanna: Fire Frequency Effects on Stand Structure and Dynamics
Ecological Applications, 2001
Although it is well known that fire can exert strong control on stand structure, composition, and dynamics in savannas and woodlands, the relationship between fire frequency and stand structure has been characterized in few of the world's savanna and woodland ecosystems. To address this issue in temperate oak-dominated ecosystems, we studied the effects of fire frequency on stand structure and dynamics in oak savanna and woodland stands that had been burned 0-26 times in 32 yr, in the Anoka Sand Plain region of Minnesota (USA). Seedling densities declined with increasing fire frequency, but differentially, for northern pin oak (Quercus ellipsoidalis), black cherry (Prunus serotina), serviceberry (Amelanchier sp.), and red maple (Acer rubrum). Bur oak (Q. macrocarpa) seedling density was not sensitive to fire frequency. Frequent burning (at least three fires per decade) prevented development of a sapling layer and canopy ingrowth. Low-frequency burning (fewer than two fires per decade) produced stands with dense sapling thickets. Reductions in overstory density and basal area from 1984 to 1995 were observed for all stands burned two or more times during that period. Basal area declined by 4-7% per year, and density declined by 6-8% per year in stands burned four or more times. Mortality rates in burned stands were higher for northern pin oak (50%) than for bur oak (8%). Northern pin oak mortality was highest for small trees (Ͻ 20 cm dbh) and lowest for mature trees (30-40 cm dbh); mortality increased with fire frequency. Bur oak mortality declined with increasing fire frequency. Attempts to preserve and maintain savannas as a viable ecosystem type in this region will require a long-term commitment to restoration-based management, with prescribed fire as a central tool. Burn frequency treatments with four or more fires per decade produce similar reductions in stem density and stand basal area but may lead to unsustainable oak tree populations. Within this general range, fire frequencies at a decadal scale should be chosen to address other management objectives, including suppressing shrubs and promoting increased cover of grasses and other herbaceous species. Fire management with a long-term view may also require periodic respites to allow for new cohorts of mature oak trees.
Ecosphere, 2021
Due to decades of fire suppression, much of the Upper Midwest savanna habitat has converted to oak woodland. In efforts to restore oak savanna habitat, fire has been re‐introduced in many of these woodlands. A primary purpose of these burns is to kill the fire‐sensitive mesophytic tree species, which had established themselves during the decades of fire suppression, reduce the number of understory trees, and preserve the larger more widely spaced oaks. It is clear from ongoing efforts that restoring oak savannas will require frequent fires over decades, but frequent fires over the long term can also threaten the desirable oaks. Long‐term demographic studies at savanna restoration sites experiencing frequent fires are necessary to determine the extent to the frequent burns are supporting and/or confounding restoration goals. Results presented here are from a twenty‐five‐year demographic study of an Upper Midwest bur oak (Quercus macrocarpa) savanna/woodland experiencing frequent fire...
Tree Density and Fire Scarring in Minnesota Oak Savanna: Implications for Restoration
Due to fire suppression subsequent to European settlement, Midwestern oak savanna has become one of the rarest ecosystems in North America, with only 0.02% of the original range surviving today. Because of the necessity of fire in perpetuating this ecosystem, restoration and management is difficult, especially because little is known about original conditions and fire dynamics of oak savanna. To address these uncertainties, fire scarring was studied at one of the longest-managed remnants of oak savanna at the Cedar Creek Natural History Area in Central Minnesota, which has been burned periodically since 1964. Fire scars lead to a lower life expectancy, therefore high levels of scarring can indicate the beginnings of a shift towards prairie or oak scrub. Both contact and non-contact scarring are prevalent in oak savanna at Cedar Creek, with scarring on as much as 80% of trees over 10 cm DBH. Contact scarring is more prevalent in areas with higher tree densities prior to the start of ...
Changes in Hoosier Prairie Oak Savanna During 27 Years of Prescribed Fire Management
The Michigan Botanist, 2007
Hoosier Prairie Nature Preserve, located in northwestern Indiana, protects a rare and unusually high quality example of a Midwestern (USA) oak savanna. Although many savannas in the region have been lost to agriculture, urbanization, and fire suppression, parts of the 178 hectare preserve never lost its historic community structure. A program of prescribed burning was initiated in 1978 and monitoring of two 10 × 10 m sample areas (Blocks) began in 1979. Throughout the 27 year observation period each Block retained a distinct understory composition even though subjected to similar fire regimes. At the same time, each underwent notable and individualistic changes from their original species composition (SSI = 64-69%) but continued to support a remarkably high diversity of xeric and mesic forbs. Native species richness ranged from 34-58 species per Block and as high as 16.8 species per 0.67 m 2 quadrat. Additionally, according to the Floristic Assessment metrics, the species quality of contemporary Hoosier Prairie is comparable (mean C = 4.9) to that expected in regional pre-settlement oak savanna communities.
Forest Ecology and Management, 2012
The survival and growth of oak advance regeneration is often limited by shade-tolerant species that are abundant in the understory of oak stands. Evidence of historic burning has prompted the use of prescribed fire as a tool to improve the competitive status of oak regeneration in mature stands. A primary shortfall of fire effects research in oak forests has been a lack of long-term studies on the effects of multiple fires. Here we describe the effects of repeated fires on stand structure and tree regeneration over a 13year period in mature mixed-oak forests located in southern Ohio, USA. Three stands were burned 3-5 times from 1996 to 2005 with low-intensity dormant-season fires, and two stands remained unburned. Woody vegetation was sampled periodically on nine 0.125 ha plots per stand. Plots were located across the upland landscape and were characterized by an Integrated Moisture Index. Fire altered stand structure by reducing the density of large saplings (3.0-9.9 cm DBH) and midstory trees (10-25 cm DBH) by 76% and 34%, respectively. Fire had little impact on trees >25 cm DBH. Small saplings (1.4 m tall to 2.9 cm DBH) were dynamic over time on dry plots that were burned. After being repeatedly topkilled from year 1-8, the small sapling layer had redeveloped on dry burned plots by year 13 and species composition had shifted from dominance by shade-tolerant species to a more equal distribution of shade-tolerants, oaks + hickories, and sassafras. The density of oak + hickory and sassafras advance regeneration (stems 30 cm tall to 2.9 cm DBH) was significantly greater on burned plots than on unburned plots in year 13, though variability among plots was high. Advance regeneration of shade-tolerant species was equally abundant on burned and unburned plots. Density of oak + hickory advance regeneration in year 13 was positively related to its weighted frequency (a surrogate for size and abundance) in year 0 (r 2 = 0.67, p < 0.0001) and inversely related to stand density (r 2 = 0.33, p < 0.0001) and canopy cover (r 2 = 0.31, p < 0.0001), both of which were reduced by fire. Although oak + hickory advance regeneration was more abundant on burned plots, we conclude that other methods (e.g., herbicide, partial cutting) are necessary to further reduce stand density and promote the development of larger oak + hickory regeneration, particularly on mesic sites.
Vegetation changes underway in oak woodland and savanna communities in the eastern and midwestern United States, primarily a result of reduced fire frequency or fire absence, include increased tree density and shading and loss of species diversity in the ground layer. However, some habitats, particularly on dry-mesic to xeric sites, retain considerable restoration potential, and insights are needed for directing management efforts, such as with prescribed fire, where they can be most effective. This paper examines overstory and ground layer interactions in flatwoods, barrens, and dry-mesic woodland habitats, together with fire effects, and highlights structural characteristics relevant to ecological condition and restoration potential.
Atti del Secondo Congresso Internazionale di Selvicoltura = Proceedings of the Second International Congress of Silviculture, 2015
Variability in historic fire regimes in eastern North America resulted in an array of oak savannahs, woodlands and forests that were dominant vegetation types throughout the region. In the past century, once abundant savannahs and woodlands have become scarce due to conversion to agriculture, or development of forest structure in the absence of fire. In addition, the future dominance of oak forests is uncertain due to chronic low regeneration potential of oak across the region and insufficient overstory recruitment. Restoration of oak savannahs and woodlands, and sustaining oak forests are primary goals for land management agencies and conservation organizations. Insights learned from fire history research can be used to guide silviculture prescriptions to achieve these goals. Restoration of oak savannahs and woodlands requires a long-term regimen of prescribed burning, but it takes a combination of prescribed fire, timber harvesting and forest thinning to efficiently produce desired structure and composition. Sustaining oak savannahs and woodlands requires an occasional longer fire-free period to allow for replacement of the overstory by recruitment of trees from the reserve of oak sprouts that have accumulated in the understory. Prescribed fire is useful for sustaining oak forests, but it must be used judiciously to minimize timber damage and decreases in value. Integrating fire in a silvicultural prescription that uses the shelterwood regeneration method to promote competitive oak reproduction has been successfully applied in the eastern US to sustain oak forests. Restoration of oak ecosystems is possible but requires innovative combinations of traditional practices, including prescribed burning.
Effects of Prescribed Fire on Sand Shinnery Oak Communities
Journal of Range Management, 2001
Sand shinnery oak (Quercus havardii Rydb.) communities are shrublands extending from northern Texas and western Oklahoma southward into the Chihuahuan Desert. They are dominated by sand shinnery oak, a member of the white oak group. Structure and composition of sand shinnery oak communities in relation to natural disturbances, such as fire, have not been adequately investigated. The objectives of this study were to determine the influence of fire on shrub composition and vegetation structure of sand shinnery oak communities, and to determine the persistence of structural and compositional changes. Data were collected on Black Kettle National Grassland (BKNG) in western Oklahoma during the growing seasons of 1998 and 1999. Vegetation measurements included line transects, visual obstructions, heights, cone of vulnerabilities, shrub patch sizes, and shrub patch densities were used to estimate functional group canopy cover, shrub composition, and structure of sand shinnery oak communities. One growing season after fire, burned sand shinnery oak communities had significantly less shrub cover (P < 0.01) than unburned communities (38 vs. 51%). Height of vegetation was lower 1 and 2 growing seasons after fire (26 and 35 cm, respectively) (P < 0.05) than unburned communities (44 cm). Visual obstruction was lower the first (30%) and second (40%) year after fire (P < 0.01) compared to unburned communities (59%). Cone of vulnerability indicated significantly more open structure one growing season after fire. After 4 growing seasons, all measures of structure in burned communities were similar to those in unburned communities. We found no differences in composition of shrub species between burned and unburned sites (P = 0.55). Two fire events, 2 growing seasons apart, had less influence on vegetation structure than the initial fire. Sand shinnery oak communities appear to be highly resilient to periodic disturbance by fire. Prescribed fire is an effective tool for short-term alteration (< 3 growing seasons) of sand shinnery oak structure; however, rapid recovery following fire does not indicate any long-term changes in vegetation structure and composition.
2008
We document an increase in oak and hickory advance regeneration, depending on landscape position, in the sixth year following mechanical thinning and repeated prescribed fires in southern Ohio, USA. Oak-dominated communities provide a multitude of human and natural resource values throughout the eastern United States, but their long-term sustainability is threatened throughout the region by poor regeneration. This study was established to assess regeneration following midstory thinning (late 2000) and prescribed fire application (2001 and 2005) at two sites in southern Ohio. Each of the four 20+ ha treatment units (two thin and burn, two untreated controls) were modeled for long-term moisture regime using the integrated moisture index (IMI), and a 50 m grid of sampling points was established throughout the units. Vegetation and canopy openness were sampled at each gridpoint before and after treatments, in 2000, 2001, 2004, and 2006. The thin and burn treatment generally resulted in more advance regeneration (>50 cm height) of oak and hickory. The second fires in 2005 created additional landscape heterogeneity by causing variable tree mortality, and thus canopy openness, across the IMI gradient. The drier landscape positions generally had more intense fires, more canopy openness, and more oak and hickory advance regeneration; several other tree species also exhibited marked landscape variation in regeneration after treatments. Though advance regeneration of several competing species became abundant after the initial treatments, the second fires reduced the high densities of the two major competitors, Acer rubrum and Liriodendron tulipifera. Two simple models were developed: (1) a model of oak ''competitiveness'' based on the plot data related to advance regeneration of oaks and competitors and (2) a model estimating the probability of a plot becoming 'competitive for oak' based on canopy openness, IMI class, and number of oak and hickory seedlings present. For dry or intermediate sites with at least 5000 oak and hickory seedlings/ha, opening the canopy to 8.5-19% followed by at least two fires should promote oak and hickory to be 'competitive' over about 50% of the area. However, no appreciable oak and hickory regeneration developed on mesic sites. Overall, these results suggest promise for partial harvesting and repeated fires as a management strategy to reverse the accelerating loss of oak dominance in the central hardwoods region. Published by Elsevier B.V.