Historical Fire Regimes and Stand Dynamics of Xerophytic Pine–Oak Stands in the Southern Appalachian Mountains, Virginia, USA

Abstract

Fire-dependent yellow pine (Pinus) forests are included within the temperate deciduous forest of eastern North America. These forests, which occupy dry slopes and typically contain xerophytic oaks (Quercus), have receded under fire suppression. Understanding historical fire regimes is essential for interpreting and managing these stands. To characterize fire history and vegetation dynamics, we conducted a dendroecological study of fire-scarred trees and age structure in pine stands at four sites in the Appalachian Mountains. Fire interval estimates suggest that before fire suppression began in the early to middle 1900s, fires occurred at approximately three- to eleven-year intervals. Short intervals were probably maintained in part by large-extent fires that spread from sparse ignition points. Fire frequency showed no long-term temporal trend (e.g., no wave of fire) from the middle 1700s through early 1900s despite land–use intensification, including industrial logging and associated wildfires during the late nineteenth and early twentieth centuries. Fire occurrence was associated with drought at two sites. Age–structure analyses evoke pyrogenic pine–oak communities that predated industrial disturbances and persisted under a regime of frequent, mixed-severity fires that was likely maintained through a positive feedback with the flammable vegetation. Competing species were established under more recent fire suppression, however, and are poised to replace the pines.

北美东部的温带落叶林包括火生黄松林（松树）。这些通常包括旱生橡树（栎树）、位于干燥山坡的森林, 由于灭火措施已经消退。了解历史火灾情况, 对于解释和管理这些森林至关重要。为了描述火灾历史和植被变化, 我们对阿巴拉契亚山脉四个松树林地的火灾痕迹和年龄构成进行了树木生态学研究。对火灾间隔的估算表明, 在20世纪初至中期开始的灭火行动之前, 大约每隔3到11年发生一次火灾。从稀疏燃点蔓延开来的大火, 可能部分导致了火灾的时间短间隔。尽管19世纪末到20世纪初土地利用加剧（包括工业伐木及其相关野火）, 但从18世纪中期到20世纪初, 火灾频率没有长期的时间趋势（例如, 没有火波）。两个林地的火灾与干旱有关。对年龄构成的分析, 唤起了工业扰动之前的火生松树和橡树群落。该群落一直存在于频繁、多种程度的火灾中、并可能由可燃植被的正反馈所维持。然而, 最近的灭火行动, 带来了持续取代松树的竞争物种。

Los bosques del pino amarillo (Pinus) que dependen del fuego se incluyen dentro de los bosques deciduos templados de la parte oriental de Norteamérica. Estos bosques, que ocupan las laderas secas y que típicamente contienen robles xerofíticos (Quercus), se han reducido bajo la supresión por fuego. Comprender los regímenes históricos de los incendios forestales es esencial para interpretar y manejar estos arbolados. Para caracterizar la historia de los incendios y la dinámica de la vegetación, llevamos a cabo un estudio dendroecológico de los árboles que fueron chamuscados por el fuego, y de la estructura de edades en arbolados de pino, en cuatro sitios de los Montes Apalaches. Los estimativos de intervalos de incendios sugieren que antes de que empezara la supresión por fuego, desde principios hasta mediados de los años 1900, los incendios se presentaban con intervalos de entre tres y once años. Los intervalos cortos probablemente se mantuvieron en parte por incendios de gran extensión que se extendieron a partir de puntos de ignición dispersos. La frecuencia de los incendios no muestra una tendencia temporal de largo plazo (e.g., sin onda de fuego) desde mediados de los años 1700 hasta principios de los 1900, a pesar de la intensificación en el uso del suelo, incluyendo la extracción industrial de madera, y de los incendios asociados con dicha actividad durante el siglo XIX tardío y los comienzos del XX. La ocurrencia de incendios estuvo asociada con la sequía en los dos sitios. Los análisis de la estructura de edades evocan comunidades pirogénicas de pino–roble que predatan las perturbaciones industriales y persistieron durante un régimen de incendios frecuentes y de severidad mixta que probablemente se mantuvo por medio de una retroalimentación positiva con la vegetación inflamable. Sin embargo, gracias a una más reciente supresión por fuego se establecieron allí especies competidoras, que están prontas a remplazar los pinos.

Key Words:

• fire frequency
• fire history
• mesophication
• Pinus pungens
• Pinus rigida

关键词:

• 火灾频率
• 火灾历史
• 中生植物化
• 红松
• 刚松。

Palabras clave:

• frecuencia de incendios
• historia de los incendios
• mesoficación
• Pinus pungens
• Pinus rigida

Acknowledgments

We are especially grateful for the cooperation of Steve Croy and Elaine Kennedy Sutherland of the U.S. Forest Service. We thank Henri Grissino-Mayer, Sally Horn, Ken Orvis, and Wayne Clatterbuck for ideas and help with fieldwork. Also, for assistance with fieldwork and sample preparation and analysis, we thank John Aldrich, George Annis, Beth Atchley, Jessica Brogden, Beth Buchanan, Anna Compton, Carol Croy, Pamela Dalal, James Dalton, Alexis Green, Justin Hart, Jason Hattersley, Ashley Heaton, Kenneth Hickman, Jennifer Hoss, Herbie Huffman, Mitch Kerr, Adam Krustchinsky, Nelson Lafon, Lisa LaForest, Evan Larson, Daniel Lewis, David Mann, Stockton Maxwell, Alison Miller, Nate Morgan, Jesse Overcash, Zach Pennington, Michelle Pfeffer, Paul Rindfleisch, Preston Roberts, Butch Shaw, Lauren Spencer, Kirk Stueve, Chris Underwood, Saskia van de Gevel, Jeremiah Wagstaff, Philip White, and Danny Wright. This article was greatly improved by the suggestions of two anonymous reviewers.

Additional information

Funding

This research was funded by the National Interagency Fire Center’s Joint Fire Science Program through cooperative agreements with the George Washington and Jefferson National Forests and by the National Science Foundation.

Notes on contributors

Charles W. Lafon

CHARLES W. LAFON is a Professor in the Department of Geography at Texas A&M University, College Station, TX 77843. E-mail: [email protected]. His research interests include vegetation patterns and their interactions with climate, terrain, and human land use.

Georgina G. DeWeese

GEORGINA G. DeWEESE is a Professor of Geography in the Department of Math, Science, and Technology at the University of West Georgia, Carrollton, GA 30018. E-mail: [email protected]. Her research interests include dendroarchaeology and dendroclimatology.

William T. Flatley

WILLIAM T. FLATLEY is an Assistant Professor in the Department of Geography at The University of Central Arkansas, Conway, AR 72035. E-mail: [email protected]. His research interests focus on the intersection between forests, climate, disturbance, and human land use.

Serena R. Aldrich

SERENA R. ALDRICH is a Professor of Geography at Blinn College, Bryan, TX 77802. E-mail: [email protected]. Her research interests include dendroecology and vegetation dynamics in the Appalachian Mountains.

Adam T. Naito

ADAM T. NAITO is an Assistant Professor in the Department of Earth, Environmental, and Geographical Sciences at Northern Michigan University, Marquette, MI 49855. E-mail: [email protected]. His research interests include landscape ecology, physical geography, geographic information systems and remote sensing applications, rangeland and forest ecology, ecological modeling, fire ecology, and biogeography.