Fire History of the Sierra de Manantlán Biosphere Reserve in Western México

Abstract

A dendropyrochronological study was conducted in the pine and pine-oak forests of the Las Joyas Scientific Research Station in the Sierra de Manantlán Biosphere Reserve located in the Sierra Madre del Sur mountain range in western México. This study was undertaken to expand our understanding of historical fire frequency in that region and to inform future fire and land management decisions. Objectives included development of a master tree-ring width chronology for the Biosphere Reserve, determination of whether tree rings are a viable source of information about historical fires in this ecosystem, reconstruction of the historical fire frequency in pine-dominated forests, and investigation of the seasonality of fires. Tropical pines present several difficulties for tree-ring research including missing, false and diffuse rings, which make crossdating of these trees challenging. This study, which is the first dendrochronological fire history study south of the Tropic of Cancer in western México, demonstrates that tree rings from tropical <italic>Pinus douglasiana</italic> and <italic>Pinus herrerae</italic> can be used in fire history studies. Across the study site, seventeen unique fire years were identified between 1938 and 2009 with a mean fire-return interval of four years and a range of one to fourteen years. Most fires occurred early in the growing season, coinciding with agricultural fires prior to the start of summer monsoon rains.