Monitoring the short-term effects of prescribed fire on an endemic mollusk in the dry forests of the eastern Cascades, Washington, USA

The restoration of natural fire regimes has emerged as a primary management objective within fire-prone forests in the interior western US. However, this objective becomes contentious when perceived to be in conflict with the conservation of rare or endemic species. We monitored the effects of two forest restoration treatments, spring- vs fall-prescribed burning, on the density of the endemic Tiny Canyon mountainsnail (Oreohelix sp.). We used a randomized block design with three replicates of each of the treatments and controls, and analyzed our data using multivariate repeated measures analysis of variance. We conducted pre-treatment surveys for mountainsnails and post-treatment surveys at three time periods: within two weeks of the treatment, the next snail season following the treatment (next spring or fall), and one year following the treatments. We did not detect any statistically significant differences in mountainsnail densities as a result of the spring-burn or fall-burn treatments, time of survey, or treatment × time interaction. The burns resulted in a fine-scale mosaic that included un-burned and lightly burned areas that acted as refuge for mountainsnails. We recommend that the application of prescribed burning as a restoration treatment within mountainsnail habitat be conducted under prescriptions that create a mosaic of burn conditions, including small unburned areas, and that prescribed fire return intervals mimic natural fire intervals (10–40 years).

Research highlights
► We conducted an adaptive management experiment to monitor the effects of prescribed fire on an endemic mountainsnail in the dry forests of eastern Washington.
► Results showed that the burn prescriptions created a fine-scale mosaic of burn intensities, not significantly reducing mountainsnail densities.
► Carefully applied prescribed fire implemented under proper conditions is a valuable tool to restore dry forests and increase the resilience of habitat for mountain snails.