Beetle Response to Seasonal Prescribed Fire in Blue Oak (Quercus douglasii) Woodlands of Big Chico Creek Ecological Reserve

ABSTRACT\ud BEETLE RESPONSE TO SEASONAL PRESCRIBED FIRE IN BLUE\ud OAK (Quercus douglasii) WOODLANDS OF BIG CHICO CREEK\ud ECOLOGICAL RESERVE\ud by\ud Mark Louis Lynch\ud Master of Science in Biological Sciences\ud California State University, Chico\ud Spring 2011\ud Fire is an integral component of terrestrial ecosystem processes. The timing,\ud intensity and frequency of fires influence ecosystem responses throughout the world.\ud Prescription burns have been widely reintroduced into fire-adapted systems in order to\ud restore natural processes, control exotic species, and other unwanted vegetation. The\ud majority of studies examining the effects of prescribed fire have predominately focused\ud on vascular vegetation; largely ignoring species in higher trophic levels. Beetles occupy\ud multiple trophic levels as consumers, serving as decomposers, herbivores, predators,\ud and scavengers. In order to improve our understanding of arthropod responses to\ud seasonal variation in prescribed fire, I examined the effects of spring (late wet-season)\ud and fall (early wet-season) prescribed fires on ground cover structure (bare ground, leaf\ud litter, plant stem density) and ground-dwelling beetle guilds in blue oak (Quercus\ud Douglassii) woodlands of Big Chico Creek Ecological Reserve (BCCER), Butte\ud County, California. The study was conducted on twelve quarter hectare (50 m x 50 m)\ud sites. Ground cover and beetles were sampled pre-treatment in April and early May\ud 2007, followed by burning four sites (spring treatment) in late May 2007. Four more\ud sites were burned (fall treatment) in early November 2007, with the four remaining sites\ud left unburned (control). Post treatment sampling of ground cover and beetles occurred\ud in April and early May 2008. Burn Severity was similar between spring and fall burn\ud treatments, but fall burns experienced the highest variability in burn severity between\ud sties. Bare ground increased and leaf litter decreased significantly in both spring and\ud fall burn sites. Plant stem density decreased in fall burns, but did not change in spring\ud burns. Overall beetle density decreased in fall and spring burn sites, but the differences\ud were not significant between treatments. Beetle density in fall burn treatments tended to\ud be lower than spring sites, but the response may have been complicated by temporal\ud recovery between fall and spring treatments. With respect to guilds, seed eaters showed\ud a strong negative correlation to burn severity and bare ground but a positive correlation\ud to leaf litter, suggesting bare ground was associated with vital resource losses. Fire\ud prescription studies conducted in California most often implement fire treatments with\ud the support of professional private/government fire crews allowing burns to take place\ud in drier conditions than allowed by burn permits issued to the public. The differences in\ud prescription timing between public burn periods and that allowed by professional fire\ud crews may affect plant and animal species differently due to the phenology and activity\ud of species present at the time of burn prescriptions. Although fires decreased beetle\ud density, results of the study did not show wet-season burn timing (spring and fall burn\ud prescriptions) to have a negative effect in ground-dwelling beetle assemblages. The\ud decrease in plant stem density in fall burns but not in spring burn sites suggests burn\ud timing influenced plant stem density response and could prove useful in land\ud management planning. Thus, burn timing appears to have significantly affected plant\ud response, but had minimal influence on beetle response; suggesting spring and fall burn\ud prescriptions can be utilized as a management tool without a dramatic impact on beetle\ud guild assemblages present.CSU, Chic