Small Mammal Response to Temporal Variations of Prescribed Fire in Blue Oak Woodlands

Transcription

1 Mark Lynch Small Mammal Response to Temporal Variations of Prescribed Fire in Blue Oak Woodlands Introduction Fire is an integral component of terrestrial ecosystem processes. Naturally the intensity and frequency of wildland fires burn on a wide-ranging scale (Kilgore 1987, Skinner and Chang 1996), to which ecosystems have adapted (Skinner and Chang 1996). A consecutive series of intense fire seasons early in the twentieth century raised concern among land managers in fire prone environments. Overwhelmed with fear a national fire plan was created aiming to suppress wildland fires and reduce the threat to human developments. Following several decades of fire suppression, we began to experience frequent, high intensity fires across the country (Swetnam 1993) predominately caused by increased fuel loads (ref). To curb this trend land managers began the use of prescribed fire as a restoration tool to improve ecosystems deprived of fire (Dickmann & Rollinger 1997). Prescriptions are typically issued outside of the natural fire regime when the threat of escape is considerably lower. However little is known about the potential complications this can create for the ecosystems involved. Fire-adapted ecosystems vary in burn frequency/intensity. Species have acquired various adaptive strategies to withstand or depend on fire regimes that are natural to their respective environments. Many researchers believe that species coevolved with fire, resulting in biologically diverse systems adapted to a variety of fire regimes (Chang 1996). Following an extremely active fire season of 1910, efforts were employed to decrease the frequency of fires as settlement of the western United States increased (Hann & Bunnell 2001). Succeeding zero tolerance policies across the country, fire frequency markedly dropped until the 1980 s. During the years of fire suppression forest fuel loads increased to dangerous levels, subsequently setting the stage for severe catastrophic fires in ecosystems which would have otherwise been naturally devoid of such events (Conard et al. 2001). Increasingly severe wildfire seasons raised concern about the future of our forests. Land managers realized the need to reevaluate fire policies across the country. The California Fire Plan (California Department of Forestry and Fire Protection 1996) suggested the use of fire to reduce burn severity in habitats carrying excess fuel loads. Subsequently the controversial use of fire has greatly increased over the last decade on both private and public lands. As projected, burn severity on lands treated with prescribed fire drastically declined. Additionally some plant species suffering recruitment losses have successfully began to regenerate: Ponderosa Pine, Giant Sequoia and Quaking Aspen (Kilgore 1972, Fule et al. 2004). California consists of several ecotypes, most of which are adapted to varying fire regimes. Only a select few have been reintroduced to fire. Even fewer have been examined by scientists trying to understand the implications of fire reintroduction. Within this complex of California ecosystems, endemic blue oak woodlands constitute the most abundant hardwood type across the state. Covering over three million acres of Sierran and Coastal foothill Ranges, blue oaks (Quercus douglasii) are poorly regenerating across their range of historical distribution (Swiecki and Bernhardt 1998, McClaran and Bartolome 1989). Concerns about regeneration have been an issue for a century, dating back to observations by Jepson (1910) and Sudsworth (1908). Human activity is most responsible for impeding adequate regeneration of blue oaks. Disturbances such as livestock grazing, mechanical cutting, introduced exotic grasses, and fire suppression constitute the greatest threats to successful regeneration (Swiecki and Bernhardt 1998).

2 Several studies suggest blue oaks are fire tolerant opposed to being fire dependent. (Standiford et al. 1997, Peterson and Reich 2001, Regan and Agee 2004, Swiecki and Bernhardt 1998). Fire studies in blue oak woodlands have demonstrated potential benefits to seedling recruitment and sapling development by removing vegetation that competes for light, soil moisture, and nutrients (Mclaran and Bartolome 1989). Limited research has examined the effects of prescribed fires during different seasons on the vegetation types found in Blue Oak woodlands (Pollack and Kan, 1998; DiTomaso, 1999; Meyer and Schiffman, 1999). The results of these studies have shown that differences in seasonal timing and frequency have different effects on different plant species. Timing the prescription of controlled burns is a function of several environmental variables. Fire is commonly employed during Spring and Fall when wildland fire threats are low, allowing safer control of burns. Unfortunately, this contrasts with the natural fire regime, to which the ecosystem is adapted, presenting potential problems for both flora and fauna.. This is of great concern considering oak woodlands provide habitat for more vertebrate wildlife species than any other vegetation type in California (Airola 1988, Ohmann and Mayer 1987). Small mammals are at the base of the consumer trophic level and also serve as seed dispersers (Fitzgerald et al. 2001). Ubiquitous across the state, small mammals are suitable candidates for studying ecosystem health in a multitude of habitats. Small mammal response to fire is not well understood. Following prescribed burn events in chaparral and desert grasslands, small mammal abundance and richness may decline the first year but populations return to equilibrium by the end of the second year (Cook 1959, Bock and Bock 1978, Groves and Stennhof, 1988). Population reductions are attributed to habitat change rather than fire-caused mortality (Schramm 1970, Beck 1972, McGee 1982, Shramm and Willcotts 1983, Dubis et al. 1988). Nesting behavior has a prominent affect on small mammal species ability to withstand burn events. Subterranean nesters are generally safe from fire, depending on the heat and duration of the burn. Ground nesting species experience the greatest population fluctuations, lacking safe refuge from the fire (Chang 1996). Studies have not examined seasonal variation in prescribed fire on small mammals. Most researchers have investigated spring or fall burns, but not a comparison of the two (Ref). The timing of prescription is of great importance based on the dispersal and avoidance ability of the species present (Ref). By answering the following research questions I hope to improve our understanding of the relationship between prescription fire timing and small mammal response in blue oak woodlands. Research questions: How does prescribed fire affect small mammal response in blue oak woodlands? Do small mammals respond differently to spring and fall prescribed fire? Materials and Methods The study will be conducted on the Big Chico Creek Ecological Reserve (BCCER) managed by the CSU, Chico Research Foundation. The reserve is located in the Northern Sierra Nevada foothills, 10 miles east of Chico, CA. The plots range in elevation between 700 ft. to 1800 ft. and are spatially distributed north to south throughout the entire reserve. Twelve study plots 50x50 meters will be selected in blue oak woodlands with a herbaceous understory dominated by European annual grasses. Four plots will be untreated (controls), four burned in the spring and four burned in the fall The Modified Whittaker (ref) vegetation sampling method will be applied to determine vegetation density, structural composition and species area curves.(details) Small mammal sampling will be conducted using a combination of drift fences with pitfall and funnel traps. Mediumsized Sherman live traps will be dispersed through the remainder of the plot. Three drift fences each twenty meters in length and positioned 120 degrees from each other will extend out from the center of each plot. One five gallon bucket

3 will serve as a pitfall trap on the end of each drift fence and one funnel trap will occupy the opposite end of the fence. Twenty five Sherman traps will be spaced 10 meters apart in each plot. The species, sex, age, and weight will be documented. Each specimen will be numbered using the toe clipping method Trapping will be conducted in two, fiveday intervals each season. Sherman traps will be baited with millet and supplied with cotton balls to prevent hypothermia in captured animals. A broadcast burn of low intensity will be implemented each treated plot. Four plots will be burned in the spring and four in the fall. Prescription burns will be issued conducted with the permission and guidance of California Department of Forestry officials. Depending on specific conditions, burns will be conducted with the support of a fire crew to aid in control of the fire. All burns will be confined to half-acre plots. A fuel break one meter wide will be created around the perimeter of each treatment. Collected data will be analyzed to determine the affect varying fire regimes have on small mammals and the re-growth of vegetation. Budget Materials (36) five gallon $6.00 ea. = $216 (36) funnel $8.00 ea. = $288 (36) drift $25.00 ea. = $900 (50) small Sherman $12.00 ea. = $600 (5) small mammal ear $17.00 (100/box) ea. = $85 (1) ear tag $25.00 ea. = $25 Bait (rolled oats, peanut oil, sunflower seeds, cotton) = $200 (1) $50.00 ea. = $50 (1) $75.00 ea. = $75 (2) 50 meter $35.00 ea. = $70 Total Materials = $2509 Travel Gas: miles/trip = 400 miles/season 400 miles x 5 cents/mile = $980

4 Total Travel = $980 Personnel Salary Vegetation sampling: 12 4hrs/site = 48 hrs/season Animal sampling: 12 5hrs/site = 60 hrs/season Total hrs/season = 108 Total 4 seasons = $12.00/hr. = $ Total Salary = $ Total Budget = $

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