Density-Dependent not -Independent Factors Influence Roosevelt Elk Recruitment in the Bald HIlls of Redwood National Park
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Density-independent and -dependent factors are known to influence population dynamics of Roosevelt elk (Cervus elaphus roosevelti). The strength of influence of both kinds of factors depends on abundance relative to K carrying capacity. I examined the influence of density, climatic variables, and prescribed fire on juvenile recruitment in an elk population in Redwood National Park, California, USA, from 2002 to 2015. In the Park, prescribed fire is used to reduce conifer and redwood (Sequoia sempervirens) encroachment into meadows and is not used to manage elk habitat. Consequently, prescribed fire might have a density-independent influence on juvenile recruitment and population dynamics because it is implemented without regard to elk population dynamics. Fire is also known to increase elk food supplies, but whether fire might have a positive influence on recruitment depends on the population size relative to K. Using a time series of elk counts conducted during winter from 2002 to 2015, abundance of elk varied from 190 to 279. Output from a Gompertz state-space model and expectation from the standard logistic model estimated K to be between 275 and 340 over the course of the study period. An Akaike Information Criterion model selection analysis of 36 linear regressions estimating juvenile recruitment considered abundance, prescribed fire, and climatic influences. Population abundance alone had the strongest influence on juvenile recruitment. My findings may be affected by the population being below K carrying capacity during most of the time series analyzed. Furthermore, prescribed fire might not have influenced recruitment because of inconsistent burning.