Short-Term Effects of Repeated Wildfires in Oak-Juniper Woodlands

• Published in: Fire ecology Vol. 9; no. 3; pp. 64 - 79
• Main Authors: Reemts, Charlotte M., Hansen, Laura L.
• Format: Journal Article
• Language: English
• Published: Cham Springer International Publishing 01.01.2013; Springer Nature B.V
• Subjects: Composition; Density; Dominant species; Ecology; Forestry; Growing season; Juniperus ashei; Life Sciences; Mesas; Military bases; Oak; Quercus; Regeneration; Research Article; Species composition; Stems; Understory; Vegetation; Wildfires; Woodlands; United States > US; Texas; repeated fires; Ashe juniper; Edwards Plateau; oak-juniper woodlands; crown fire
• ISSN: 1933-9747; 1933-9747
• DOI: 10.4996/fireecology.0903064

Fire can shape both the structure and composition of vegetation communities, especially those dominated by species with different regeneration strategies. The dominant species of oak-juniper communities in central Texas include resprouters (oaks [ Quercus spp.]) and a reseeder (Ashe juniper [ Juniperus ashei Buchholz]). We studied the effects of two overlapping wildfires (1996 and 2009) on oak-juniper woodlands on Fort Hood Military Reservation, Texas, USA. We estimated burn severity and measured vegetation regeneration along permanent transects in once-burned, twice-burned, and nonburned areas. Burn severity was highly variable, but was higher in 1996 than in 2009. In the first growing season after the second fire (2009), understory stem density was 3 to 4 times higher than in 1996, but that difference had disappeared by the third growing season. Overstory density did not differ after the two fires, but density on slopes was 3 to 10 times higher than on mesas. Overall species composition was similar after the two fires, but differed from nonburned areas due to the absence of Ashe juniper. Ashe juniper was still absent from twice-burned areas in 2011, whereas small numbers of junipers (21 ± 34 stems ha −1 ) had colonized the once-burned areas within three years. Our data suggest that wildfires controlled the historical distribution of Ashe juniper, but not of resprouting species, in the Edwards Plateau, and that long intervals between wildfires are required for Ashe juniper to become a canopy dominant in these woodlands.