Grandmother Mountain Wilderness Study Area - Post-Burn Assessment

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Wildfire disturbance occurs in nearly all ecosystems of the Pacific Northwest. A burned area reflectance classification (BARC) map is often used to assist in mitigating potential deleterious effects of wildfire disturbance. A primary basis for the BARC map, the differenced normalized burn ratio (dNBR) is calculated by comparing pre-burn and post-burn multispectral imagery. While an initial fire severity assessment is made immediately following a wildfire, an extended assessment may be made in years following the wildfire event. Whitebark pine (Pinus albicaulis) is a keystone species in subalpine and timberline ecosystems of the Pacific Northwest and Northern Rocky Mountains. The species is in decline throughout its range due to the combined effects of exotic fungal disease, insect outbreaks, climate change, and, particularly, altered fire disturbance regimes. In much of its range whitebark pine is dependent on fire to persist on the landscape. Fire disturbance serves to reduce competition, enhance the capability of whitebark pine to defend against insect infestation and resist disease, create new early-seral whitebark pine habitat, and to promote whitebark pine seed caching. In August 2015 lightning ignited the Breezy and Crater fires within Grandmother Mountain Wilderness Study Area (WSA). This study provides documentation of the severity of the 2015 fire effects and their influence on the distribution and characteristic of whitebark pine habitats within Grandmother Mountain WSA. The results contribute to, or inform, mapping, inventory, and monitoring whitebark pine conservation and management actions on Bureau lands. Twenty-seven plots were sampled within 11 sampling units. High mortality occurred in subalpine fir (Abies lasiocarpa) on the Breezy Fire units, leaving few live trees within some sample units. Soil burn severities were also relatively high within the Breezy Fire, compared to the Crater Fire. An extended fire severity assessment is best correlated with the 2017 field observations with approximately 67% agreement. Probable explanations for discrepancies between the two are differences in the response of herbaceous versus forest vegetation to the 2015 fires. While herbaceous vegetation was partially recovered by the 2016 growing season, tree mortality continued in forest vegetation into the 2017 growing season. The 2015 Breezy and Crater fires clearly created new early-seral whitebark pine habitat and appear to have enhanced whitebark pine seed caching habitats. Monitoring within the burned areas should be extended into future years to track the success of whitebark pine establishment within Grandmother Mountain WSA.

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Reference Code: U18RUS02IDUS <br>

Full Citation: Rust, S. K. 2018. Grandmother Mountain Wilderness Study Area - Post-Burn Assessment. Prepared by Nature’s Capital, LLC for United States Department of the Interior, Bureau of Land Management, Coeur d’Alene District Office, Coeur d’Alene, Idaho. 27 pp. plus appendices <br>

Location: BOTANY: PLANT SPECIES: {Pinus albicaulis} <br>

Keywords: whitebark pine, Pinus albicaulis, Grandmother Mountain, Wilderness Study Area, WSA <br>