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ABSTRACT: 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 13-year 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 (r2 = 0.67, p < 0.0001) and inversely related to stand density (r2 = 0.33, p < 0.0001) and canopy cover (r2 = 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.
Forest Ecology and Management 01/2012; 286:87-100. · 2.49 Impact Factor
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ABSTRACT: Oak dominance is declining in the central hardwoods region, as canopy oaks are being replaced by shade-tolerant trees that are abundant in the understory of mature stands. Although prescribed fire can reduce understory density, oak seedlings often fail to show increased vigor after fire, as the canopy remains intact. In this study, we examine the response of tree regeneration to a sequence of repeated prescribed fires followed by canopy gap formation. We sampled advance regeneration (stems >30 cm tall) in 52 gaps formed by synchronous mortality of white oak (Quercus alba L.); 28 gaps were in three burned stands and 24 gaps were in three unburned stands. Five years after gap formation, unburned gaps were being filled by shade-tolerant saplings and poles and were heavily shaded (7% of full sun). By contrast, tolerant saplings had been virtually eliminated in the burned gaps, which averaged 19% of full sun. Larger oak and hickory regeneration was much more abundant in burned gaps, as was sassafras, while shade-tolerant stems were equally abundant in burned and unburned gaps. Our results suggest that the regeneration of oak, particularly that of white oak, may be improved with multiple prescribed fires followed by the creation of moderate-sized canopy gaps (200-400 m2).
Canadian Journal of Forest Research 01/2012; 42:303-314. · 1.68 Impact Factor
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ABSTRACT: Question: What was the role of fire during the establishment of the current overstory (ca. 1870-1940) in mixed-oak forests of eastern North America? Location: Nine sites representing a 240-km latitudinal gradient on the Allegheny and Cumberland Plateaus of eastern North America. Methods: Basal cross-sections were collected from 225 trees. Samples were surfaced, and fire scars were dated. Fire history diagrams were constructed and fire return intervals were calculated for each site. Geographic patterns of fire occurrence, and fire-climate relationships were assessed. Results: Fire was a frequent and widespread occurrence during the formation of mixed-oak forests, which initiated after large-scale land clearing in the region ca. 1870. Fire return ranged from 1.7 to 11.1 years during a period of frequent burning from 1875 to 1936. Fires were widespread during this period, sometimes occurring across the study region in the same year. Fires occurred in a variety of climate conditions, including both drought and non-drought years. Fires were rare from 1936 to the present. Conclusions: A variety of fire regime characteristics were discerned. First, a period of frequent fire lasted approximately 60 years during the establishment of the current oak overstory. Second, fire occurred during a variety of climate conditions, including wet climates and extreme drought. Finally, there was within-site temporal variability in fire occurrence. These reference conditions could be mimicked in ongoing oak restoration activities, improving the likelihood of restoration success. Nomenclature: Gleason & Cronquist (1991).
Journal of Vegetation Science 01/2009; · 2.77 Impact Factor
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ABSTRACT: We used dendrochronology to examine the influence of past fires on oak and maple establishment. Six study units were located in southern Ohio, where organized fire control began in 1923. After stand thinning in 2000, we collected basal cross sections from cut stumps of oak (n = 137) and maple (n = 204). The fire history of each unit was developed from the oaks, and both oak and maple establishment were examined in relation to fire history. Twenty-six fires were documented from 1870 to1933; thereafter, only two fires were identified. Weibull median fire-return intervals ranged from 9.1 to 11.3years for the period ending 1935; mean fire occurrence probabilities (years/fires) for the same period ranged from 11.6 to 30.7years. Among units, stand initiation began ca. 1845 to 1900, and virtually no oak recruitment was recorded after 1925. Most maples established after the cessation of fires. In several units, the last significant fire was followed immediately by a large pulse of maple establishment and the cessation of oak recruitment, indicating a direct relationship between fire cessation and a shift from oak to maple establishment.Nous avons eu recours à la dendrochronologie pour étudier l'influence du feu dans le passé sur l'établissement du chêne et de l'érable. Six unités expérimentales ont été localisées dans le sud de l'Ohio où la lutte organisée contre les feux a débuté en 1923. Après que des peuplements eurent été éclaircis en 2000, nous avons collecté des sections radiales sur des souches de chêne (n = 137) et d'érable (n = 204). Dans chaque unité, l'historique des feux a été établi à partir des chênes et l'établissement du chêne et de l'érable a été étudié en lien avec l'historique des feux. Vingt-six feux ont été documentés de 1870 à 1933; par la suite, seulement deux feux ont été identifiés. L'intervalle médian de Weibull entre les feux variait de 9,1 à 11,3 ans pour la période se terminant en 1935; la probabilité moyenne d'occurrence de feux (années/feux) pendant la même période variait de 11,6 à 30,7 ans. Parmi les unités, l'origine des peuplements remonte aux environs de 1845 à 1900 et pratiquement aucun chêne n'a été recruté après 1925. La plupart des érables se sont établis après que les feux eurent cessé. Dans plusieurs unités, le dernier feu important a immédiatement été suivi d'une importante vague d'établissement de l'érable et de l'arrêt du recrutement du chêne, indiquant qu'il y a une relation directe entre la cessation des feux et le changement marqué par l'établissement de l'érable au lieu du chêne.
Canadian Journal of Forest Research 04/2008; 38(5):1184-1198. · 1.68 Impact Factor
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Some assembly required: preserving nature in a fragmented landscape Natural Areas Association 34th Annual Conference: NAA 2007 Conference Abstracts, Cleveland, OH; 01/2007
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The Ecological Society of America 91st annual meeting: icons and upstarts in ecology, Washington, DC; 01/2006
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14th Central Hardwood Forest Conference, Wooster, OH; 01/2004
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The Ecological Society of America 89th annual meeting. Lessons of Lewis and Clark: ecological exploration of inhabited landscapes, Portland, OR; 01/2004
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International Journal of Wildland Fire. 01/2004; 13(3):1-12.
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Ecological Society of America 88th annual meeting; 01/2003
