Prescribed Fire and its Effects on Forested Ecosystems
Since 1990, Coweeta scientists and collaborators have investigated the impacts of prescribed burning with long-term (ongoing), interdisciplinary, ecosystem approaches. Studies have been conducted on the effects of prescribed fire on ecosystem processes such as net primary production, nutrient and carbon cycling, and vegetation dynamics (regeneration, compositional changes, mortality, diversity) in a number of forest types.
Coweeta’s research approach uses watershed-scale (water quality and quantity) and within watershed scale (plot level changes in nutrient and carbon cycling, vegetation dynamics) assessment of ecosystem responses to restoration burning. The watershed approach facilitates extrapolation of small-scale disturbances to larger landscape units. One unique aspect that is being addressed is the long- and short-term impacts of prescribed fire on ecosystem sustainability, using rates and pool sizes of carbon, nutrients, and water as key indicators of sustainability.
Prescribed burning in southern Appalachian ecosystems has many potential benefits: (1) reduction of fuel loads to minimize the risk and impacts of wildfire; (2) reduction of the evergreen understory to promote regeneration of desirable species such as oaks; (3) increased diversity of plants, small mammals, birds, amphibians, and insects; (4) stimulation of fast-growing new shoots to increase productivity; and (5) stimulation of nutrient cycling rates to increase site productivity. After nearly a century of exclusion, re-introduction of fire into the current forests of the southern Appalachians will have varying affects on ecosystem properties and vegetation structure and composition depending on fire type (intensity, severity, frequency, timing, and scale) and forest type (current species composition and structure, slope, soils, microclimate, and fuel load). Therefore, there is a need for more thorough investigation on the effects of prescribed fire on ecosystem processes in multiple forest types before widespread application. In addition, more knowledge is needed on the interactions between historical fire regimes, current ecosystem structure and function, and ecosystem responses to re-introduction of prescribed fire. Coweeta scientists are continuing their research efforts to understand the role of fire in forests of the Southern Appalachian Mountains.
Four large-scale prescribed burning projects in cooperation with the Nantahala National Forest of North Carolina, Chattahoochee National Forest of Georgia, and Cherokee National Forest of Tennessee are ongoing. Specific research questions to be addressed by prescribed and restoration burning are: 1) How does burning affect carbon and nutrient cycling and what are the short- and long-term effects on productivity and sustainability? 2) What are the effects of burning on regeneration patterns, biodiversity, and understory productivity? 3) How does burning affect wildlife habitat? and 4) How does burning affect stream water quality?
Wine Spring Creek restoration burn
The study area is located in the Nantahala National Forest of the southern Appalachian Mountains, western North Carolina (35°N latitude, 83°W longitude) and is part of the Wine Spring Creek Ecosystem Management Project. Wine Spring Creek watershed is within the Blue Ridge Mountain District of the Blue Ridge physiographic province. Three tributaries (Wine Spring Creek, Bearpen Creek, and Indian Camp Branch) converge into Wine Spring Creek that drains into Nantahala Lake at the western edge of the watershed boundary. The Wayah Ranger District, Nantahala National Forest, North Carolina prescribe burned the approximately 300 ha study area in April 1995. The fire was ignited by helicopter at the bottom of the south facing slope near the stream and created a mosaic of fire intensities, ranging from lightly burned (<80°C) at the low slope to heavily burned (>800°C) along upper slopes and ridges (Vose et al. 1999). On the ridge, the stand-replacing fire consumed understory vegetation and ignited the crowns in areas of highest fire intensity. Research demonstrated that prescribed stand restoration burning in mixed pine/hardwood ecosystems has positive benefits to pine regeneration, understory production and diversity, and habitat diversity (Elliott et al. 1999). Stream and soil chemistry showed no negative effects following burning (Vose et al. 1999). Small mammals and herpetofauna were unaffected (Ford et al. 1999) and groups of forest floor microarthropods responded differently to the burn treatment (Crossley et al. 1999).
Conasauga River Watershed restoration burn
Six sites were established in the Cherokee National Forest, TN (35° N latitude, 84° W longitude) and Chattahochee National Forest, GA (34° N latitude, 84° W longitude). Sites were selected on the basis of similarity in overstory (Pinus virginiana, Pinus echinata, Quercus prinus, Q. coccinea, and Q. alba) and understory (Pinus strobus) composition, elevation, soils, topography, aspect, and presence of a perennial stream. The Ocoee Ranger District, Cherokee National Forest and the Cohutta Ranger District, Chattahoochee National Forest prescribed burned the four sites in March 2001. Fires were ignited with a drip torch using primarily backing-fire, lighting solid strips only along the ridge tops and allowing the fire to back down to the streams.
Before and after the prescribed fire, Coweeta scientists measured soil CO2 evolution; litterfall; large down wood; forest floor (small wood, litter, and fermentation+humus) mass, carbon and nitrogen pools; soil, soil solution, and stream chemistry; and vegetation (herbaceous, shrubs, and trees). Indices of soil nitrogen (N) availability showed no significant response to burning on any of the sites (Hubbard et al. 2004). Similarly, soil water NO3 - and NH4 +, and stream N did not increase after burning on any of the sites (Elliott and Vose 2005a). In the overstory, only a few small sized (5.0 cm< dbh<15.0 cm) trees were killed by the fire. However, significant mortality and subsequent regeneration in the understory was found in the first growing season after the burn. Virginia pine and white pine decreased in the understory; while, yellow poplar (Liriodendron tulipifera), red maple (Acer rubrum), scarlet oak (Quercus coccinea), and blueberries (Vaccinium spp.) increased in abundance (Elliott and Vose 2005b).
Joint Fire Science Program (JFSP)
In 2002, the JFSP provided funding for a combination of re-measurement of established studies and initiation of additional studies in mesic, mixed-hardwood forests in North Georgia (Chattahooche National Forest) and western North Carolina (Nantahala National Forest). This forest type is the most extensive component in the southern Appalachians, yet there have been no systematic studies of ecosystem response to prescribed fire. In total, funding provided by the JFSP allowed detailed (following the same protocol) and long-term assessments of ecosystem responses to prescribed burning in major forest types in the southern Appalachian region.
The objectives of the research are twofold: (1) to document and synthesize information on the historical and contemporary fire regimes, and (2) to evaluate the effects of prescribed fire on ecosystem structure and function along a moisture/productivity gradient from xeric, pine-hardwood to mesic, mixed-hardwood ecosystems in the southern Appalachian region. The linkage between the two project objectives is based on the premise that significant improvements in the application of prescribed fire and in the understanding of fire effects are possible with an increased knowledge of historical fire regimes.
Objective 1: Document and synthesize information concerning pre- and post-settlement fire regimes in mixed-hardwood forests in the southern Appalachian region by using pollen/charcoal records, Cherokee Indian tribal records and archeological sites, and USFS and State Forest Service fire records.
Paleoecological data derived from charcoal and pollen in lakes and bog sediments provide reconstruction of environmental/fire history and a comparison with other documented accounts of vegetation patterns related to fire history (Clark, unpublished data). The synthesis of current information from the literature and other historical documents (Cherokee Indian Tribal records) established the historic locations of the Indian populations, the kinds of sites which were usually chosen for villages and agricultural fields (Gragson, in review), and how fire was used by Native Americans to modify their landscapes (Cooley 2004). A detailed analysis of USFS and State Forest Service fire records established the historical and contemporary fire regimes, both wildfire and prescribed fire, on state and federal lands in the southern Appalachians (Jurgelski and Gragson 2004, unpublished report).
Objective 2. Evaluate the effects of prescribed fire in mixed deciduous forests on fuel load reduction and ecosystem structure and function.
Most studies in the southern Appalachians have focused on pine/hardwood mixtures on xeric sites. Since these forest types occupy only a small portion of the landscape (about 5%), we know very little about the role of fire or its effects in most of the forested areas of the southern Appalachians. Strong topographic and edaphic variation creates gradients that determine vegetation composition, net primary productivity, and susceptibility and response to disturbance. To fully understand potential uses and effects of fire in the southern Appalachians, studies need to be conducted across vegetation and climatic gradients. To address this objective, Coweeta scientists are using a combination of ongoing and new research sites to assess short and long-term responses along these gradients. The ecosystems studied and compared are xeric, low productivity pitch pine (P. rigida)/hardwood forests; dry, moderate productivity shortleaf (P. echinata)/Virginia pine (P. virginiana)/oak forests; and mesic, high productivity, mixed/hardwood (L. tulipifera/Q. rubra) forests.
Ocoee Restoration Burn
In 2005, the JFSP provided funding to conduct watershed scale studies on the effects of fuel reduction and restoration treatments on pine/hardwood forests (Ocoee Ranger District, Cherokee National Forest) that have been severely impacted by the recent (1999-2003) southern pine beetle (Dendroctonus frontalis Zimmerman) outbreak. Federal, state, and private land managers are now challenged with large-scale implementation of management activities that: (1) reduce the increased fire risk to widespread dead, fallen and dying trees, particularly in the wildland-urban interface, (2) restore forests destroyed by the SPB, and (3) reduce the potential for development of stand conditions that promote SPB outbreaks and other stand conditions and subsequent future wildfire risk.
This research approach uses within watershed scale (stand level changes in nutrient and carbon cycling, vegetation dynamics) assessment of ecosystem responses to restoration treatments. The objectives of the proposed research are: (1) to compare and quantify fuel load reduction methods (cutting dead pine and undesirable hardwoods, material left on site followed by prescribed fire; prescribed fire only; and no treatment) in pine/hardwood forests heavily impacted by southern pine beetle induced tree mortality, and (2) to evaluate the effects of further restoration treatments including planting shortleaf pine (Pinus echinata) and seeding native bluestem grasses on ecosystem structure and function in these pine-hardwood ecosystems in the southern Appalachian region. We hypothesize that fuel reduction treatments (cutting and burning) followed by planting native pine and seeding native grasses will restore these ecosystems to a sustainable pine/hardwood ecosystem (i.e., more open savannas that are less susceptible to future SPB outbreaks and have lower wildfire risk).
Modeling the effects of prescribed fire on nutrient loads in the southeastern US
Fire can play a significant role in altering runoff, sediment, and nutrient transport in aquatic and terrestrial ecosystems. The typical impact of fire is an immediate change in the physical properties of the soil and forest floor surface, alterations in nutrient uptake and processing, and changes in the amount and distribution of nutrient pools within the ecosystem. While there is potential for wildfire and prescribed burns to pose risks to water quality in the southeastern US, there has been little effort to specifically model the effects of prescribed burning on water quality at large spatial scales. This research addresses the needs of land managers to estimate the post-fire risks of flooding, erosion, and contamination of drinking water from sediment and nutrients.
Our approach is to use a combination of field studies and modeling to assess the impacts of varying fire regimes on water quality. For the modeling, we are applying and testing nutrient, sediment, and hydrologic cycling models across the mountains, piedmont and coastal plain physiographic regions in the southeastern US. Field study sites were located in the Nantahala National Forest in the southern Appalachians, the Uwharrie National Forest in the piedmont region and the Croatan National Forest in the coastal plain region. Portable automated samplers were installed to measure water quality and quantity, soil solution lysimeters and overland flow collectors were installed to determine surface vs. subsurface contributions of nutrients and sediment (Vose et al. 2005). We are focusing on nitrogen (NO-3, NH+4), phosphorous (PO-4) and sediment because they are key indicators of ecosystem response to disturbance and are important water quality parameters.
Summary
Prescribed fires in the southern Appalachians can be successful in reducing undesirable midstory species such as evergreen shrubs and invasive white pine (Pinus strobus), with little to no effect on sediment and nutrient transport to streams (Clinton et al. 2003, Elliott and Vose 2005a). Maintaining an intact forest floor and promoting rapid vegetation recovery is critical to minimizing the magnitude and duration of sediment transport (surface erosion), sediment delivery (suspended solids) and subsequent water quality responses (Elliott and Vose 2006, Clinton and Vose 2007). Fire managers can influence the effects of prescribed fire on water quality and other ecosystem properties (e.g., soil nutrient loss, vegetation recovery) by limiting fire severity and fire size. Understanding the effects of fire on southern Appalachian ecosystems is complex, because of the long period of fire exclusion and variation in and among ecosystems in terms of community composition and structure, fuel quality and quantity, climate, soil properties, and topography. Scientists are continuing their work on restoration of degraded ecosystems, evaluating a combination of treatments such as thinning overstory trees and midstory shrubs followed by fire and planting desirable species, using the watershed scale approach to evaluate the impacts on ecosystem resources.
Coweeta Scientific Publications related to fire
Clinton, B.D.; Vose, J.M. & Swank, W.T. 1993. Site preparation burning to improve southern Appalachian pine-hardwood stands: vegetation composition and diversity of 13-year-old stands. Canadian Journal of Forest Research 23:2271-2277.
Clinton, B.D.; Vose, J.M. & Swank, W.T. 1996. Shifts in aboveground and forest floor carbon and nitrogen pools after felling and burning in the southern Appalachians. Forest Science 42:431-441.
Clinton, B.D.; Vose, J.M.; Swank W.T.; Berg, E.C. & Loftis, D.L. 1998. Fuel consumption and fire characteristics during understory burning in a mixed white pine-hardwood stand in the southern Appalachians. USDA Forest Service, Southern Research Station, Research Paper SRS-12, Asheville, NC: 8 p.
Clinton, B.D. & Vose, J.M. 2000. Plant succession and community restoration following felling and burning in the southern Appalachians. In W.K. Moser and C.F. Moser (eds.). Fire and forest ecology: innovative silviculture and vegetation management. Tall Timbers Fire Ecology Conference Proceedings, No. 21, Tall Timbers Research Station, Tallahassee, FL: pp 22-29.
Clinton, B.D.; Vose, J.M.; Knoepp, J.D. & Elliott, K.J. 2003. Stream nitrate response to different burning treatments in southern Appalachian forests. In K.E.M. Galley, R.C. Klinger, and N.G. Sugihara (eds.). Proceedings of the Fire Conference 200: The First National Congress on Fire Ecology, Prevention, and Management, San Diego, CA Nov 27-30, 2000. Tall Timbers Research Station, Tallahassee, FL: pp. 174-181.
Clinton, B.D. & Vose, J.M. 2007. Forest floor and woody fuels consumption and nitrogen loss following prescribed fire: A comparison of prescription types in the Southern Appalachians. In Proceedings, 15th Central Hardwood Forest Conference, Knoxville, TN, 27 Feb -1 Mar 2006. USDA Forest Service General Techical Report SRS-* .
Cooley, N.E. 2004. Understanding Traditional Knowledge for Ecological Restoration: A qualitative study with the Eastern Band of Cherokee. M.S. Thesis, Northern Arizona University, Flagstaff, AZ: 65 p.
Crossley, D.A., Jr. & Lamoncha, K.L. 1999. Response of forest soil microarthropods to a forest regeneration burn at Wine Springs (southern Appalachians). In Proceedings of First biennial North American forest ecology workshop; 1997 June 24-26; Raleigh, NC: pp. 1-15.
Douglass, J.E. & Van Lear, D.H. 1983. Prescribed burning and water quality at ephemeral streams in the Piedmont of South Carolina. Forest Science 29:181-189.
Elliott, K.J. & Vose, J.M. 1993. Site preparation burning to improve southern Appalachian pine-hardwood stands: photosynthesis, water relations, and growth of planted Pinus strobus during establishment. Canadian Journal of Forest Research 23:2278-2285.
Elliott, K.J. & Vose, J.M. 1994. Photosynthesis, water relations, and growth of planted Pinus strobus L. on burned sites in the southern Appalachians. Tree Physiolology 14:439-454.
Elliott, K.J. & Vose, J.M. 1995. Evaluation of the competitive environment for white pine (Pinus strobus L.) seedlings planted on prescribed burn sites in the southern Appalachians. Forest Science 41:513-530.
Elliott, K.J.; Hendrick, R.L.; Major, A.E.; Vose, J.M. & Swank, W.T. 1999. Vegetation dynamics following stand-replacement fire in the southern Appalachians. Forest Ecology and Management 114:119-213.
Elliott, K.J.; Vose, J.M. & Swank, W.T. 2000. Fire as a silvicultural tool to improve southern Appalachian Pine-hardwood stands. In W.K. Moser and C.F. Moser (eds.). Fire and forest ecology: innovative silviculture and vegetation management. Tall Timbers Fire Ecology Conference Proceedings, No. 21, Tall Timbers Research Station, Tallahassee, FL: p. 198.
Elliott, K.J.; Vose, J.M. & B.D. Clinton. 2002. Growth of eastern white pine (Pinus strobus L.) related to forest floor consumption by prescribed fire in the southern Appalachians. Southern Journal of Applied Forestry 26:18-25.
Elliott, K.J.; Vose, J.M.; Clinton, B.D. & Knoepp, J.D. 2004. Effects of understory burning in a mesic, mixed-oak forest in the southern Appalachians. In R.T. Engstrom, K.E.M. Galley, and W.J. de Groot (eds.). Proceedings of the 22nd Tall Timbers Fire Ecology Conference: Fire in Temperate, Boreal, and Montane Ecosystems. Tall Timbers Research Station, Tallahassee, FL: pp 272-283.
Elliott, K.J. & Vose, J.M. 2005b. Effects of prescribed burning on shortleaf pine (Pinus echinata Mull.)/mixed-hardwood forests. Journal of the Torrey Botanical Society 132:236-251.
Elliott, K.J. & Vose, J.M. 2006. Effects of prescribed fire on southern Appalachian ecosystems. In Proceedings of the 3rd International Fire Ecology & Management Congress, special symposium titled: “Changing spatiotemporal dynamics of fire regimes in the Appalachian Mountains”, San Diego, CA, November 13-17, 2006. Washington State University, Extension. 6 pp.
Elliott, K.J. & Vose, J.M. 2006. Fire effects on water quality: A synthesis of response regulating factors among contrasting ecosystems. In D.L. Fowler (compiler), Proceedings of the 2nd Interagency Conference on Research in the Watersheds, USDA Forest Service, Southern Research Station, Coweeta Hydrologic Laboratory, Otto, NC, May 16-18, 2006: pp. 77-87.
Ford, W.M.; McGill D.W.; Laerm, J.; Meszel, M.A. & McCay T.S. 1999. Effects of a community restoration fire on small mammals and herpetofauna in the southern Appalachians. Forest Ecology and Management 114:233-243.
Hubbard, R.T.; Clinton, B.D.; Vose, J.M.; Knoepp, J.D. & Elliott, K.J. 2004. Nutrient and carbon pools and fluxes following stand restoration burning in oak/pine forest types in the Conasauga River Watershed. Forest Ecology and Management 190:311-321.
Jurgelski, W. unpublished report (2003). Appalachian Fire History – Overview, potential sources, and possible directions. Report submitted to Coweeta Hydrologic Laboratory ( Dec. 12, 2003), Otto, NC: 22 p. in Coweeta Files.
Knoepp, J.D. & Swank, W.T. 1993. Site preparation burning to improve southern Appalachian pine hardwood stands: nitrogen responses in soil, soil water, and streams. Canadian Journal of Forest Research 23:2263-2270.
Knoepp, J.D. & Swank, W.T. 1995. Comparison of available soil nitrogen assays in control and burned forested sites. Soil Science Society of America Journal 59:1750-1754.
Knoepp, J.D.; Vose, J.M. & Swank, W.T. 2004. Long-term soil responses to site preparation burning in the southern Appalachians. Forest Science 50:540-550.
Knoepp, J.D.; DeBano, L.F. & Neary, D.G. 2005. Chapter 3: Soil chemistry. In D.G. Neary, K.C. Ryan, and L.F. DeBano (eds.). Fire effects on soil and water. USDA Forest Service, Rocky Mountain Research Station, General Technical Report RMRS-GTR-42, Vol. 4, Fort Collins, CO: pp. 53-71.
Love, J.P.; Vose, J.M. & Elliott, K.J. 2007. Effects of restoration burns on macroinvertebrates and salamanders in southern Appalachian pine-oak forests. Journal of the North Carolina Academy of Science 123:22-34.
Neary, D.G. & Currier, J.B. 1982. Impact of wildfire and watershed restoration on water quality in South Carolina’s Blue Ridge Mountains. Southern Journal of Applied Forestry 6:81-90.
Swift, L.W.; Elliott, K.J.; Ottmar, R.D. & Vihnanek, R.E. 1993. Site preparation burning to improve southern Appalachian pine-hardwood stands: fire characteristics and soil erosion, moisture, and temperature. Canadian Journal of Forest Research 23:2242-2254.
Vose, J.M. & Swank, W.T. 1993. Site preparation burning to improve southern Appalachian pine-hardwood stands: aboveground biomass, forest floor mass, and nitrogen and carbon pools. Canadian Journal of Forest Research 23:2255-2262.
Vose, J.M.; Swank, W.T. & Clinton, B.D. 1994. Fire, drought, and forest management influences on pine/hardwood ecosystems in the southern Appalachians. In Proceedings of the 12th Conference on Fire and Forest Meteorology, October 26-28, 1993, Jekyll Island, GA: pp. 232-238.
Vose, J.M.; Swank, W.T.; Clinton, B.D.; Hendrick, R. & Major, A.E. 1997. Using fire to restore pine/hardwood ecosystems in the Southern Appalachians of North Carolina. In Fire effects on threatened and endangered species and habitats: Symposium proceedings; 1995 November 13-16; Couer de Alene, ID; International Association of Wildland Fire, Spokane, WA: pp. 1-6.
Vose, J.M.; Swank, W.T.; Clinton, B.D.; Knoepp, J.D. & Swift L.W., Jr. 1999. Using stand replacement fires to restore southern Appalachian pine-hardwood ecosystems: effects on mass, carbon, and nutrient pools. Forest Ecology and Management 114:215-226.
Vose, J.M. 2000. Ecosystem perspectives on using prescribed fire to achieve desired future conditions. In W.K. Moser and C.F. Moser (eds.). Fire and forest ecology: innovative silviculture and vegetation management. Tall Timbers Fire Ecology Conference Proceedings, No. 21, Tall Timbers Research Station, Tallahassee, FL: pp 12-17.
Vose, J.M.; Laseter, S.H.; Sun, G.; & McNulty, S.G. 2005. Stream nitrogen response to fire in the southeastern U.S. In 3rd International Nitrogen Conference, 12-16 Oct. 2004, Nanjing China. Edited by S. Zhu, K. Minami, and G. Xing. Science Press USA, Inc. pp. 577-584.
Waldrop, T.A.; Welch, N.T.; Brose, P.H.; Elliott, K.J.; Mohr, H.H.; Gray, E.A; Tainter, F.H. & Ellis, L.E. 2000. Current research on restoring ridgetop pine communities with stand replacement fire. In D.A. Yaussey (ed.). Proceedings: Workshop on fire, people, and the central hardwood landscape, 2000 March 12-14; Richmond, KY. General Techinical Report NRS-274, USDA Forest Service, Northeastern Research Station, Newton Square, PA: pp 103-109.
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