Fire Regimes of the Central Appalachian Mountains

Principal Investigators:

Charles W. Lafon, Department of Geography, Texas A&M University, College Station, TX 77843-3147; Phone: (979) 862-3677; Fax: (979) 862-4487; E-mail: clafon@geog.tamu.edu

Henri D. Grissino-Mayer, Department of Geography, University of Tennessee, Knoxville, TN 37996; Phone: (865) 974-6029; Fax: (865) 974-6025; E-mail: grissino@utk.edu

Federal Cooperators:

Elaine K. Sutherland, Rocky Mountain Research Station, Forestry Sciences Laboratory, P.O. Box 8089, Missoula, MT 59807; Phone: (406) 542-4169; Fax: (406) 543-2663; E-mail: esutherland@fs.fed.us

Steven Q. Croy, George Washington & Jefferson National Forests, 5162 Valleypointe Parkway, Roanoke, VA 24019; Phone: (540) 265-5153; Fax: (540) 265-5145; E-mail: scroy@fs.fed.us

Douglas G. Raeburn, Shenandoah National Park; 3655 U.S. Highway 211 East, Luray, VA 22835; Phone: (540) 999-3393; Fax: (540) 999-3601; E-mail: doug_raeburn@nps.gov

Project Duration: June 1, 2003 - May 31, 2006

Annual Funding Requested from JFSP: Year 1: $109,627; Year 2: $107,603; Year 3: $63,420
Total Funding Requested from Joint Fire Science Program: $280,650

Total Value of In-Kind and Financial Contributions: $133,396

Abstract: We propose an investigation of fire history, age structure, and successional dynamics of yellow pine stands in the Central Appalachian Mountains, which encompass parts of the Blue Ridge, Ridge and Valley, and Appalachian Plateaus. We will conduct our work on the George Washington and Jefferson National Forests and the Shenandoah National Park. Appalachian yellow pine stands, which are dominated by Table Mountain pine (Pinus pungens Lamb.) and pitch pine (P. rigida Mill.), typically occupy xeric sites. Regeneration and maintenance of the pines appear to require repeated surface fire, and occasional stand-initiating fires of greater severity. Fire exclusion appears to be preventing the establishment and maintenance of pines. Table Mountain pine, an Appalachian endemic, may largely disappear over time in the continued absence of burning. Deterioration of Appalachian pine stands has stimulated interest in the use of prescribed burning, both to regenerate pines and to reduce hazardous fuel loads, but little research on Appalachian fire regimes is available to guide fire-restoration. We will use dendrochronological techniques to date fire scars and assess the frequency, seasonality, spatial extent, and climatic relations of past fires. Age structure analysis will reveal whether pulses of regeneration have occurred, whether the pulses were associated with fire, and whether pine stands are being maintained. We will use an individual-based forest gap model to evaluate hypotheses about disturbance regimes under which the pine stands developed and to predict likely consequences of reintroducing fire. We envision that the results of our study will help fill local knowledge gaps significant to fire management plan development and implementation (Task 3, JFSP RFP 2001-3). We anticipate this information being used by land managers in developing guidelines and policies consistent with restoration of fire as an ecosystem process.

Introduction
Project Justification

Fire exerts a strong influence on the development of Appalachian forest vegetation. The prevalence of southern yellow pine (Pinus) and oak (Quercus) forests over much of the region apparently resulted, in part, from frequent, widespread burning in the past (Abrams 1992; Van Lear and Watt 1993; Williams 1998; Harrod et al. 2000). Both yellow pines and oaks possess characteristics that make them resistant to or dependent upon fire. For example, Table Mountain pine (Pinus pungens Lamb.) has serotinous cones, and many pine and oak species have thick bark (Williams 1998; Harrod et al. 2000; Sutherland and Smith 2000). Optimal yellow pine germination and seedling establishment occurs where fire reduces the depth of litter and duff on the forest floor, permitting seedling roots to reach mineral soil (Williams 1998; Harrod et al. 2000; Welch et al. 2000). Yellow pines are intolerant of shade and appear to require fires of moderate to high intensity that kill substantial portions of the dominant overstory trees (Zobel 1969; Williams 1998; Welch et al. 2000). The dramatic reduction in burning since the advent of effective fire suppression has resulted in deep litter accumulation and has permitted invasion of pine stands by more shade-tolerant (and less fire-resistant) hardwood trees and shrubs (Williams 1998; Harrod et al. 2000; Welch et al. 2000).

Deterioration of xerophytic Appalachian pine and mixed pine-oak stands has prompted concern about their continued survival. Table Mountain pine, a major component of many of these forests, is endemic to the Central and Southern Appalachian Mountains. The species is relatively rare, narrowly distributed on xeric slopes and ridgetops, and has a relatively small geographic range (sensu Rabinowitz 1981). Table Mountain pine and the associated pitch pine (Pinus rigida Mill.) will largely disappear from Appalachian landscapes in the continued absence of burning, as succession proceeds to hardwood dominance (Williams and Johnson 1990; Williams 1998). The loss of these fire-dependent pine stands has other negative consequences, in addition to decline of an endemic species. These impacts include reduction in cover and richness of herbaceous species (Harrod et al. 2000), loss of pine warbler habitat, decrease in snags used by various woodpecker species and cavity nesters, and diminishment of landscape and habitat diversity.

The deterioration of yellow pine stands in the Appalachians has stimulated interest in the use of prescribed burning to regenerate pine and restore the processes under which these forests developed (Williams 1998; Welch et al. 2000). Recent prescribed burning experiments provide insights into the fire intensities needed for pine regeneration. In fact, in 1998 JFSP funded a project by Thomas Waldrop and others to examine pine regeneration in Southern Appalachian Table Mountain pine-pitch pine stands subjected to different levels of fire intensity during prescribed burns. Published reports of such studies, which focus on pine stands in the southern Blue Ridge Mountains near the southern range limits of Table Mountain and pitch pines, emphasize that optimum pine regeneration requires moderate- to high-intensity fires that cause substantial overstory mortality (Elliott et al. 1999; Waldrop and Brose 1999; Welch et al. 2000). However, little information exists on the fire regimes that maintained the stands prior to effective fire suppression, which started in the 1920s and 1930s. Analyses of historic fire regimes are crucial both to implement and to justify restoration of fire as an ecosystem process. The only study of fire history in Central Appalachian pine forests was a small pilot project that focused on two stands in southwestern Virginia (Sutherland et al. 1995). Despite the limited scope of the study, the USFS and other land managers use it to guide fire prescription, because it is the only such study available. We propose a dendroecological study of fire history and age structure in representative Table Mountain pine-pitch pine stands across the Central Appalachian Mountains of western Virginia and eastern West Virginia. Fire history information, combined with age structure data, will provide a detailed summary of the current structure of Table Mountain pine-pitch pine populations, their relationships with past fire, and their prognosis for survival under the current fire regime. We will also sample current species composition of these stands to provide a baseline for monitoring changes that result from succession or prescribed fire. We will employ an individual-based forest succession model to develop and test hypotheses about the disturbance regime under which these stands developed and to predict likely consequences of management actions, such as reintroducing fire into existing stands. Based on the findings of our study, we will propose prescriptions for restoring fire in pine stands across the Central Appalachians. The George Washington and Jefferson National Forests are willing to apply these prescriptions, and in fact we are planning additional long-term research to monitor successional changes in stands selected for these prescriptions.

Our study will be an excellent complement to the work of Waldrop et al. that JFSP funded in 1998. Both approaches are needed to provide the information necessary for forest managers to plan prescribed burning treatments in the Appalachian region, where relatively little fire-related research has been conducted. Both yield insights into the intensity of fire required for pine regeneration. However, our work will not duplicate previous efforts, as we will focus on historic fire regimes (including frequency of surface fires, frequency of stand-initiating fires, fire seasonality, fire-climate relationships, and spatial variations in past fire regimes) as well as on long-term successional dynamics (past, present, and future). Such information can be gained only from the types of dendroecological and modeling approaches that we propose, and is precisely the kind of data needed to develop and justify long-term strategies for fuels treatments and for the restoration of fire-maintained ecosystems (Welch 1999).

Our proposal is also related to a dendroecological study funded by JFSP in 2001 and currently being conducted by Henri Grissino-Mayer, Michael Armbrister, and Michael Jenkins. The Grissino-Mayer et al. project is a relatively small, single-year study of age structure in five Table Mountain pine stands in Great Smoky Mountains National Park (GSMNP), which is located in the Southern Blue Ridge Mountains. The GSMNP research is an initial exploration of relationships of pine stand structure to past fire and other disturbances, especially periodic insect outbreaks. Grissino-Mayer et al. have sampled approximately fifteen fire-scarred trees to look for relationships between pine recruitment and fire in the stands of interest, but GSMNP restrictions against chain saw use preclude collection of more samples. The study is not intended to provide management guidelines for the larger Southern and Central Appalachian region. It would be inappropriate to extrapolate GSMNP fire regimes to the Central Appalachians, where geology, topography, vegetation, and climate differ in ways that probably influence fire frequency and behavior. For example, GSMNP has some of the wettest climatic conditions in the eastern U.S. (mean annual precipitation 57-80 inches, or 1450-2030 mm), and the Central Appalachians have some of the driest (mean annual precipitation 33-45 inches, or 850-1140 mm) (Terwilliger 1991; NCDC 2001). Studies of fire regimes in other regions reveal that such regional climatic gradients influence fire frequency and seasonality (e.g., Heyerdahl et al. 2001).

We will conduct our study on the George Washington and Jefferson National Forests and on Shenandoah National Park, where we will be permitted to use chain saws. We will be able to sample fire-scarred trees from numerous study sites distributed over a broad area. Our study will provide both local- and regional-level results from which we will develop management recommendations appropriate for specific federal, state, and private land management units (e.g., individual ranger districts).

Our research addresses Task 3 of JFSP RFP 2001-3 and will yield new insights about effects of fire on endemic flora, site-specific fire history information, and seasonality of fire and fire effects. The work will help fill local knowledge gaps significant to fire management plan development and implementation in the George Washington and Jefferson National Forests, Shenandoah National Park, and other federal, state, and private resource management agencies. We expect that our results will be useful to Cherokee National Forest, Pisgah National Forest, Monongahela National Forest, Blue Ridge Parkway, Cumberland Gap National Historical Park, New River Gorge National River, The Nature Conservancy, and state wildlife management areas, natural areas, parks, and forests. We have secured the endorsement and support of the George Washington and Jefferson National Forests, Shenandoah National Park, and other major land management agencies in the region (see enclosed letters).

Project Objectives

We have three primary objectives:

(1) To identify and characterize fire regimes (including fire frequency, seasonality, severity, spatial extent, and climatic relationships) in selected yellow pine stands. We seek to build the longest possible record of fire in order to determine the fire regime under which the stands have developed. We are interested in temporal changes as well as spatial variations in fire regimes.

(2) To evaluate the current age structure of the stands in order to assess the possible historic role of fires that we date in initiating establishment of pine cohorts.

(3) To combine this information, along with current species composition data and individual-based forest modeling, to understand current successional status of the stands and possible outcomes of future management scenarios.

Addressing these objectives will provide ecological information crucial for successful management of these forests, including the use of prescribed fire.

Background

Relatively little work has been conducted on fire regimes or the role of fire in Appalachian forests. Lightning-set fires presently occur in the Appalachians, but they recur too infrequently to have major influences over most of the landscape. In the George Washington National Forest, lightning caused 14% of fires that have occurred since 1915 (S. Croy, unpublished data). Lightning-set fires were probably uncommon in presettlement times as well (Abrams 1992; Delcourt and Delcourt 1998; Welch 1999). However, historical accounts and analyses of fossil pollen and charcoal suggest that presettlement human-set fires burned frequently and had important consequences for vegetation in the Appalachians. Annual burning by Native Americans maintained a vast prairie in the Shenandoah Valley of Virginia, and such openings were probably common along many of the major river valleys (Van Lear and Waldrop 1989; Delcourt and Delcourt 1998). Fires also spread into the surrounding mountains, maintaining open forests of oak, chestnut (Castanea dentata), and pine (Van Lear and Waldrop 1989; Delcourt and Delcourt 1998). In more remote mountainous sections, escaped campfires probably spread into the forest as Native Americans traveled through these areas (Van Lear and Waldrop 1989), and lightning-set fires may also have promoted pine dominance in some locations (Williams 1998). European colonists adopted fire practices similar to those of Native Americans (Pyne et al. 1996). Ayres and Ashe (1905) surveyed forests of the southern Blue Ridge in 1900 and 1901 and found that light surface fires were frequent over 80% of the region. More severe burning followed large-scale industrial logging in the late 1800s and early 1900s, leading to expansion of fire-adapted vegetation, such as Table Mountain pine-pitch pine forests (Williams 1998).

Work of Zobel (1969) and Welch (1999) in xeric, pine-dominated sites throughout the Appalachians illustrate the ubiquity of fire in these stands. Zobel (1969) sampled forest vegetation in Table Mountain pine stands and found that signs of fire, including soil charcoal, charred bark and logs, and fire-scarred trees, were almost universally present throughout the range of the species. Welch (1999) collected soil cores from yellow pine stands on National Forest lands throughout the southern Appalachians. Her work revealed the presence of macroscopic soil charcoal in every soil core, including cores from two sites in which no recorded fires have occurred since federal land acquisition.

Although these studies demonstrate the past occurrence of fire in Appalachian pine stands, they do not reveal the frequency, seasonality, size, or intensity of those fires. A dendroecological approach is needed for a detailed investigation of historic fire regimes under which the stands developed (Welch 1999). Harmon (1982) used dendroecological techniques to date the occurrence of fires that had scarred pines in the western portion of Great Smoky Mountains National Park. His work revealed a Mean Fire Interval (MFI) of 12.7 years between 1856 and 1940. MFI appeared to vary topographically, with highest frequency on south-facing upper slopes and lowest frequency on north-facing lower slopes.

During the Fourth Annual Dendroecological Fieldweek held in June 1993, Sutherland et al. (1995) conducted a pilot project on the fire history and age structure of Table Mountain pine stands on Brush Mountain, Virginia, in the Jefferson National Forest. This preliminary study serves as the basis for the work we propose. This study, combined with the work of Harmon (1982), described above, demonstrated that dendrochronological analyses of fire-scarred pines can be used to establish local records of fire in the eastern U.S., where such studies are virtually non-existent. Results of the Brush Mountain project suggested that prior to the mid-1900s, fires occurred approximately once per decade, usually during drought years. The work also suggested a bimodal age distribution for the stands, which is similar to results of another dendroecological study of age structure in Table Mountain pine stands on Brush Mountain (Williams and Johnson 1990). The two major recruitment events appear to be linked to two major fires at the site. The fire regime characteristic of Table Mountain pine stands on Brush Mountain is apparently one of frequent surface fires that kill understory hardwoods and expose mineral soil, punctuated occasionally by more severe burns that kill a substantial portion of the canopy trees and thereby permit major pine recruitment. Additional studies on the ecology of Appalachian yellow pine stands (e.g., Welch et al. 2000) also suggest their maintenance requires frequent surface fires and occasional stand-initiating fires.

Other major disturbance events common in the Appalachian uplands (insect outbreaks, ice storms, windstorms, and landslides) do not promote pine regeneration, except when fire is also a component of the disturbance regime. In the Appalachians, the primary canopy disturbances affecting pine stands are southern pine beetle ("SPB," Dendroctonus frontalis) outbreaks and ice storms (Williams 1998). Although such events create large canopy openings that increase light availability in the understory, they do not remove the hardwood/shrub understory that competes with pine seedlings, nor do they reduce the thick litter layer that has accumulated in the absence of fire. Further, they cause more damage to pines than to the competing hardwoods and typically accelerate succession to hardwood dominance (Williams 1998; Lafon et al. 1999). Fire suppression actually may increase the severity of SPB outbreaks by permitting development of dense, senescent stands subject to SPB outbreak. Prior to fire suppression, frequent burning maintained open stands in which SPB attack was probably restricted primarily to scattered trees that were stressed (Schowalter et al. 1981; Harrod et al. 2000). Currently, a major SPB outbreak is affecting the entire Southern and Central Appalachian region, where drought conditions since 1998 have caused increased moisture stress among the crowded, senescent pines. In addition to accelerating the conversion of thousands of acres of yellow pine to hardwood dominance, this SPB outbreak increases the potential for uncharacteristically severe wildfire that may be difficult to control.

Materials and Methods
Study Areas

Our study area includes parts of three physiographic provinces: (1) the Blue Ridge mountains along the eastern edge of the Appalachians, (2) the parallel mountains and valleys of the Ridge and Valley province in the core of the Appalachian Mountain region, and (3) the eastern edge of the dissected Appalachian Plateaus province. We will conduct most of the work on the George Washington and Jefferson National Forests, which comprise approximately 1.8 million acres (728,000 ha) of land. About 90% of this acreage is in western Virginia, and nearly all the remainder is in eastern West Virginia. A small portion is in eastern Kentucky. We will also sample stands in Shenandoah National Park, which encompasses about 200,000 acres (81,000 ha) of land in the Blue Ridge province. The climate of western Virginia and eastern West Virginia is humid, but severe droughts occur, typically at intervals of one or two decades (NCDC 2001). Strong precipitation gradients exist between the relatively dry interior valleys (annual precipitation 33 - 37 inches, or 850 - 950 mm) and the Blue Ridge and the Plateaus (over 50 inches, or 1270 mm) (Terwilliger 1991; NCDC 2000) due to orographic effects on precipitation. In addition, topographic moisture gradients resulting from effects of hillslope hydrology and aspect create pronounced vegetation patterns. Oak forests are the predominant vegetation type in the region (SAMAB 1996), and the yellow pine forests that are the focus of the proposed study are mostly restricted to xeric sites, such as ridgetops and south- to southwest-facing slopes (Whittaker 1956; Zobel 1969; Stephenson and Mills 1999). Some of the pine stands form large patches over the dry slopes of a mountain. However, most are smaller stands within a hardwood matrix. The geographic range of Table Mountain pine is centered on western Virginia, and the species is more abundant in Virginia than any other state (Della-Bianca 1990). Virginia and West Virginia are located in the southern half of the range of pitch pine (Little and Garrett 1990). These pine species occur over a wide range of elevations in the region (Della-Bianca 1990; Little and Garrett 1990) and are especially common in middle elevations.

Effective fire suppression in Virginia began with establishment of the Virginia Department of Forestry and an expansion of National Forests in the 1930s. Fire suppression continues to be a major component of forest management in Virginia and on federal lands in the region (Pyne 1982; Sarvis 1993a, 1993b; Williams 1998; USFS 2001). In recent years, however, forest managers have become interested in the use of prescribed burning to benefit oak and pine species and to reduce hazardous fuel accumulations (Sarvis 1993b; USFS 2001). US Forest Service personnel typically treat 5,000 to 12,000 acres (2025 to 4860 ha) of the George Washington and Jefferson National Forests annually with prescribed fire. Target acreage for prescribed burning on these national forests is 20,000 to 25,000 acres (8100 to 10,125 ha) per year. The study by Sutherland et al. (1995) at Brush Mountain is currently the only dendrochronological study of fire history available to guide fire management in the Central Appalachians. An ongoing study of sediment charcoal in ponds and bogs throughout western Virginia and eastern West Virginia (James Clark and Jason Lynch, Duke University) will provide a broad view of temporal trends in charcoal production over the last millennium. However, more dendroecological work is needed for precise information on past fire regimes, changes in fire regimes, spatial variations in fire frequency, and the resultant age structure of forest stands.

Our specific study sites will be clustered in several groups covering the major drainage basins of the study area. Clustering of sites will permit us to assess the extent of individual fires in an area and to provide results relevant to local fire management plan development within individual ranger districts. Distributing these clusters throughout western Virginia and eastern West Virginia will provide insights about region-level spatial patterns in fire regimes and will permit the development of broader generalizations about fire occurrence in relation to land use history and climate. The expertise of federal cooperators Steve Croy and Doug Raeburn will be employed for locating old stands that record a long history of fire. We will attempt to construct a fire chronology that extends to presettlement times.

Methods

To evaluate the pattern of fire on the landscape, we will employ a systematic sampling approach (sensu Heyerdahl et al. 2001). Plots will be laid out on a grid on each drainage, and on those grids we will collect complete cross-sections from dead pines with multiple fire scars, using a chain saw, and will cut partial cross-sections from fire-scarred living trees (Arno and Sneck 1977; Dieterich 1983; Baisan and Swetnam 1990; Sutherland et al. 1995; Heyerdahl et al. 2001). To the extent possible, we will focus our sampling on downed or standing dead trees. Oak trees also reveal fire-caused injury (Smith and Sutherland 1999). Hence, we propose to sample 1 - 2 oak trees per plot of sufficient age to have overlapped with the pine fire chronology to search for fire scars, and compare the fire-scar record of the pines and oaks. Comparing pine and oak fire chronologies will inform development of future research on fire regimes in oak forests, many of which probably need periodic fire for continued maintenance.

To determine age structure and tree species composition in each drainage, we will core trees of all species on each plot, in diameter classes representing the range of tree diameters on site. Using an increment borer, we will extract two cores from selected individuals at the base of the stem and parallel to slope contour. Age of seedlings and saplings will be determined by counting terminal bud scars and branch nodes, when possible. This method has been used effectively to determine the age of Table Mountain pines too small to core (Williams and Johnson 1990). Relevant data will be recorded for each tree from which a cross-section or core is obtained. We will collect Global Positioning System (GPS) points for mapping study sites and analyzing spatial patterns of fire.

Cross-sections will be reassembled and, if necessary, glued to plyboard. Increment cores will be glued to wooden core mounts. We will sand all surfaces using progressively finer sandpaper (40 grit through 400 grit) to create a surface on which cellular structure of the wood is readily visible under 20-30X magnification. Tree-ring patterns from all cross-sections and increment cores will be crossdated by creating skeleton plots for each sample, thereby assigning each tree ring its exact year of formation (Stokes and Smiley 1968). We will create a composite skeleton plot, or master chronology, for each stand cluster (Stokes and Smiley 1968). The master chronology will be used to crossdate each sample. If we cannot conclusively crossdate samples graphically, we will measure ring widths and enter the measured series into program COFECHA to match the sample to the master chronology statistically (Holmes 1986).

Fire dates will be recorded and archived using FHX2 software (Grissino-Mayer 1995, 2001). In addition, the seasonality of each fire will be determined and recorded by noting the approximate position of the fire scar within the annual ring (Baisan and Swetnam 1990): (1) scars in the early earlywood portion of the annual ring, (2) scars in the middle earlywood portion, (3) scars in the late earlywood, (4) scars in the latewood, (5) scars in the dormant position (between the latewood of one ring and the earlywood of the next), and (6) scars whose position cannot be determined accurately. FHX2 software will be used to develop master fire charts (Dieterich 1980) depicting the temporal and spatial patterns of past fire at each site. We will use statistical analyses to develop estimates of the Weibull Median Fire Interval, Weibull Modal Fire Interval, Upper and Lower Exceedance Intervals, and Maximum Hazard Interval (Grissino-Mayer 1999). We will also use the software to conduct Superposed Epoch Analysis (SEA) (Swetnam 1993; Veblen et al. 1999; Grissino-Mayer 2001) to assess the occurrence of fires in relation to drought. Drought data (Palmer Drought Severity Index) for the period 1895 - present will be obtained from the National Climatic Data Center website at http://www.ncdc.noaa.gov/. For conducting SEA prior to 1895, we plan to use long regional tree-ring-based drought reconstructions developed by David Stahle and collaborators for the southeastern U.S., including Virginia (Stahle and Cleaveland 1996; Stahle et al. 1998). All statistical descriptors will help model the fire regime under which the pine stands developed.

To determine the age structure of the yellow pine stands, ages of trees will be used to create frequency histograms that depict the age classes (Williams and Johnson 1990; Sutherland et al. 1995). Analysis of age structure, combined with fire history data, will yield insights about the possible role of severe fires in initiating pulses of pine regeneration. Along with stand composition data, age structure data will permit inferences about the successional trajectory of pine stands on current Appalachian landscapes.

Individual-based simulation modeling of forest succession will also provide insights about the role of fire and other disturbances in maintaining xeric pine stands in the Appalachians. Individual-based forest models, or gap models, simulate forest dynamics in greater detail than landscape fire simulation models or fire behavior models, and they also integrate climatic influences on forest processes (Miller and Urban 1999). Both detailed stand dynamics and integration of climate and fire are necessary to predict effects of burning on vegetation. Applications in the Sierra Nevada and the Rocky Mountains demonstrate the utility of gap models in fire science (Keane et al. 1996; Miller and Urban 1999, 2000). We have modified a version of the LINKAGES gap model (Pastor and Post 1985) to include more detailed canopy structure and mortality dynamics needed to simulate natural disturbances such as ice storms, wind storms, and fires, as well as harvests (Huston 1994; Lafon 2000). We have also incorporated light-water tradeoffs in tree growth and canopy structure (Huston 1994) into the model to improve simulation of temporal and spatial dynamics of forest processes. The model can produce realistic simulations both of successional changes and of spatial patterns in forest parameters (e.g., patterns of species composition and diversity along topographic moisture gradients) (Huston 1994; Lafon 2000).

Results of the proposed study will permit incorporation of an appropriate fire regime (e.g., frequency, severity) into the model and will help us modify the model to simulate fire effects in more detail. These modifications will allow us to test hypotheses about the influence of past burning on pine maintenance and the effects of fire suppression on stand structure (Williams 1998). We will compare the species composition and stand structure predicted by the model to the observed composition and structure in the stands we sample. We will also compare predicted effects of fire on tree and shrub mortality to studies that have quantified forest response to prescribed burns and wildfires in southern Appalachian pine stands (e.g., Elliott et al. 1999; Waldrop and Brose 1999; Harrod et al. 2000; Welch et al. 2000). If the model is validated by these tests, we will use alternative future management scenarios, including prescribed burning, to develop predictions of potential changes in the dynamics of existing forests. These predictions will inform our recommendations for fire prescriptions in the Central Appalachians. The model will also be applicable to simulating fire effects in other geographic areas, with minimal model modification.

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Project Duration

The project will require three years for completion. If fieldwork commences in summer 2003, analyses should be completed by 31 May 2006.

Budget