Macroscale effects of the Monument Fire on suitable habitat of the Trinity bristle snail in the Greater Trinity Basin, Klamath Bioregion, northern California

Abstract

I evaluated the impact and extent of the Monument Fire on the geographic range and suitable macrohabitat of the Trinity bristle snail (Monadenia setosa), a California endemic with limited distribution in northern California. Total area burned by the fire was ~87,984 ha or 46.0% of the species range (n = 191,156 ha). Total area of suitable macrohabitat for the species is ~107,913 ha of which 44.5% (n = 47,962 ha) was encompassed by the fire. Results show that the total area of forest cover-type vegetation and individual forest stand attributes impacted by the fire was not significantly different from areas within the species range not burned by the fire. There was no significant proportional differences in the six sequential categories of suitable macrohabitat burned by the fire (i.e., Low, Low-moderate, Moderate, Moderate-high, High, Critical suitability). The percentage of Moderate and Moderate-high suitable macrohabitat burned was only somewhat greater than predicted by the pre-fire species habitat suitability model (HSM). Many individual watersheds were encompassed by the fire and the resulting mosaic of burned watersheds was highly variable. Application of the Soil Burn Severity (SBS) map identified 8,293 ha (17.3%) of Unburned or very low burned soil, 24,191 ha (50.5%) of Low burned soil, 13,998 ha (29.2.1%) of Moderately burned soil, and 1,460 ha (3.0%) of Highly burned soil within the boundaries of the Monument Fire. When applied to categories of suitable macrohabitat, I calculated that 31,096 ha (100%) of Low to Low-moderate and 13,998 ha (96.1%) of Moderate to Moderate-high suitable macrohabitat were burned. High and Critical areas of macrohabitat suitability were much less impacted by high SBS (n = 1,461 ha [58.0%] because these regions were small in size, highly fragmented, widely dispersed across the landscape, and separated by major topographic and riverine discontinuities.