Understanding the effects of wildfire severity on deciduous browse production and moose habitat use in Interior, Alaska
Wildfire is the most common ecological disturbance in the boreal forest and recent studies predict that climate change will increase the frequency, extent, and severity of fire in Interior Alaska. Fire severity is an important control over post-fire production of deciduous species and can influence the overall quality of winter habitat for herbivores such as moose (Alces alces). The objective of this research is to evaluate the relative influence of a regenerating burn, paying particular attention to fire severity, on winter browse production and moose habitat use. We hypothesized that browse production and removal (kg/ha) estimates are greater in high severity sites than low severity sites and moose will exhibit higher rates of habitat utilization in high-severity habitat than low-severity habitat. We used 17 pre-established sites that have been stratified across burn severity, low (n=6) and high (n=11), to conduct browse assessment surveys to estimate browse production and removal. In October 2012, 26 collars were deployed on bull moose within close proximity to the Hajdukovich Creek Burn located in Delta Junction, Alaska. We used dynamic Brownian bridge movement models (dBBMM) to determine whether the regenerating burn affects habitat use patterns of moose across their home ranges.
We found that nearly 200 kg/ha of forage biomass was produced across all sites within the Hajdukovich Creek Burn, but production varied strikingly depending on the fire severity. High-severity sites produced 267 (SE=26) kg/ha and low-severity sites produced a mean of 172 (SE=16.) kg/ha. The proportion of annual browse production that was consumed by moose (offtake) also varied among fire severities. Offtake was greatest in high-severity sites with a proportional removal of 27% (SE=6%), whereas low severity sites experienced 11% (SE=4%) proportional removal. There was a significant difference in forage offtake between high-severity and low-severity sites (t=2.2, p=0.05). Preliminary results from 95% home range boundaries estimated by dBBMM show that bull moose on average show strong selection for burned habitats during autumn and early-winter months. As wildfire characteristics continue to change under a warming climate, managers can expect to see changes to plant species composition, wildlife distributions and hunting opportunities. The results from this project will contribute to our understanding of the effects of fire on an important wildlife resource in Interior Alaska.