TIMING OF PRESCRIBED BURNS AFFECTS ABUNDANCE AND COMPOSITION OF ARTHROPODS IN THE TEXAS HILL COUNTRY SALLY D. JOHNSON,KATHERINE C. HORN,AMY M. SAVAGE,STEVE WINDHAGER,MARK T. SIMMONS, AND JENNIFER A. RUDGERS* Department of Ecology and Evolutionary Biology, Rice University, Houston, TX 77005 (SDJ, KCH, AMS, JAR) Lady Bird Johnson Wildflower Center, The University of Texas at Austin, Austin, TX 78739 (SW, MTS) *Correspondent: jrudgers@rice.edu ABSTRACT—Prior research has demonstrated that fire can be an important structuring force for plant communities in prairies and grasslands. However, investigations of land-management techniques, such as prescribed fire, often overlook responses of local fauna, particularly the arthropods. In this study, we examined a previously unappreciated, although potentially important, component of fire ecology by asking, does the timing of prescribed burns alter community structure of arthropods? At a site in the Texas Hill Country, we used sweep-net sampling to collected arthropods from experimental plots that had been treated with a summer-burn or winter-burn regime. Summer-burn plots supported .170% more individual arthropods than winter burns. Although overall diversity of arthropods did not significantly differ between treatments, there were significantly more carnivorous arthropods and marginally more herbivorous arthropods after fire in summer relative to fire in winter. Effects of timing were particularly strong for Cicadellidae (leaf hoppers) and Tetragnathidae (long-jawed spiders). Our results demonstrate that timing of prescribed fire can substantially alter composition of resident communities of arthropods. Furthermore, these data highlight the importance of examining composition of the community, in addition to diversity indices, when assessing response of arthropods to land-management techniques. RESUMEN—Investigaciones previas han mostrado que el fuego puede ser una fuerza importante en la estructuracio ´n de comunidades vegetales en praderas y pastizales. Sin embargo, las investigaciones acerca de las te ´cnicas de manejo del terreno, tales como quemas prescritas, pasan por alto la respuesta de la fauna local, particularmente la de los artro ´podos. En este trabajo, examinamos un previamente poco apreciado, aunque potencialmente importante, componente de la ecologı ´a del fuego, preguntando si la temporada de quemas prescritas altera la estructura de la comunidad de los artro ´ podos. En un sitio en Texas Hill Country, usamos redes de golpeo para colectar los artro ´podos de las parcelas experimentales previamente tratadas con quemas invernales y quemas veraniegas. Las parcelas con quemas veraniegas mantuvieron .170% ma ´s individuos que las parcelas de quemas invernales. Aunque la diversidad total de artro ´ podos no difirio ´ significativamente entre tratamientos, hubo significativamente ma ´s artro ´ podos carnı ´voros y, marginalmente, ma ´s artro ´ podos herbı ´voros en el tratamiento de quemas veraniegas relativas a las invernales. El efecto de la temporada de quema fue particularmente marcado para los Cicade ´lidos (chicharritas) y Tetragna ´tidos (aran ˜as obitelas de grandes quelı ´ceros). Nuestros resultados muestran que la temporada de las quemas prescritas puede alterar substancialmente la composicio ´n de las comunidades residentes de artro ´ podos. Ası ´ mismo, estos resultados destacan la importancia de examinar la composicio ´n de la comunidad, y no so ´lo los ı ´ndices de diversidad, al evaluar la respuesta de los artro ´podos a las te ´cnicas de manejo del terreno. Historically, fire, grazing by American bison (Bison bison), and seasonal extremes in temper- ature and precipitation regulated vegetation dynamics in North American prairies and grass- lands (Parton and Risser, 1980; Risser and Parton, 1982; Diamond and Smeins, 1985; Gibson and Hulbert, 1987; Leach and Givnish, 1996; Collins et al., 1998; Knapp et al., 1999; Radeloff et al., 2000; Steinauer and Collins, 2001; Collins and Smith, 2006). Due to suppression of fire by humans, fire has been all but eliminated from most systems, and the brief but intense grazing by American bison has been replaced primarily by year-round grazing by domestic THE SOUTHWESTERN NATURALIST 53(2):137–145 JUNE 2008