Ecology Studies - 1994 Thunder Fire

Morel mushrooms after the fire.

Final Reports (PDF) Thunder Fire Report, by G. Wooten, M. Poss, and M. Larsen (3 MB PDF file). Thunder Fire Project Appendices Links: Introduction Background and Highlights Ecology Wildlife Birds Amphibians Vegetation Threats Related pages: Boreal research Boreal Okanogan

As the name suggests, the Meadows area is punctuated by both dry and wet meadow systems. Forests are mixed conifer, primarily lodgepole pine, both Douglas fir and subalpine fir and Engelman spruce and extend from 4500 to over 7000ft. Fire is an integral part of this system and the effects of past fires can be seen by the mosaic of size and age classes across the landscape. This structural diversity leads to habitat diversity and fire provides the force that keeps the system in a dynamic flux. Without it there is stagnation.

BOREAL ECOSYSTEM CHARACTERISTICS

Boreal wetlands have a number of features uncommon in low elevation Washington wetlands, including presence of earth hummocks, boreal (willow-bog birch) flora, late snow melt (mid-July is typical), short growing season, heavy snow packs, dense, but sometimes shallow peat formation underlain by sandy alluvium deposited by continental glaciation. Sphagnum formations are less common, but occasionally are dominant. Other moss associations are common around bog margins. Typically, herbaceous flora is dominated by Carex scopulorum var. prionophylla, Lupinus polyphyllus var. burkei (=L. arcticus), Trollius laxus, Epilobium spp., Carex disperma, Calamagrostis canadensis, Valeriana dioica, Valeriana sitchensis, to name a few. Introduced plant species in the Okanogan Range are still uncommon, relative to nearby areas, due to the lack of roads and trails in the the area and dense stands of "doghair" lodgepole and intervening wetlands which act in concert as a partial quarantine barriers for vectors such as livestock or hikers. This is a tenuous characteristic, however, for in many areas nearby in this same ecosystem, pristine conditions rapidly change following introduction of drought-tolerant grasses, draining of wetlands, or cutting of range driveways by livestock permittees.

CONTINENTALLY GLACIATED CHARACTER

The area is characterized by high-elevation topography with gentle slopes. The low relief contrasts with typical areas in the nearby North Cascades which are generally highly dissected by alpine and valley glaciation. Presumably, the final phase of glaciation in the Okanogan Range was the melting of the terminus of the Cordilleran ice sheet, which rounded most of the summits and cirques produced in previous alpine glacier phases (Waite, 1972). The region thus lies just north of the margin of continental glaciation that can be traced in moraines across North America. Across the continent, this narrow strip of land is characterized anomalous terrain features; glacial erratics; sandy deposits of outwash gravels and boulders; and ice-marginal channels carved by ice and/or water (E.C. Pielou, 1991).

WETLANDS

Contrasting with the nunataks are the rolling Salix/Carex wetlands occupying the depressions of Horseshoe Basin. These are relict boreal ecosystems that still retain much of the character that they developed in the wake of receding ice. They occupy streams and pockets at high elevation, where perhaps because of the low energy gradients, the soil rarely dries out. Adding to the wetness are severe summer thunderstorms which travel up the Chewuch River, ultimately to pass over the Meadows area, and which have given the Chewuch River the nickname "fire alley".

Although similar habitats are commoner to the north and west in the Rockies, the North Cascades Range does not continue extensively north of Cathedral Park (Mackinnon et. al., "Plants of Northern British Columbia" Lone Pine, 1992, map on p. 12-13). The northeastern Pasayten Wilderness and the entire Okanogan Range were completely covered by the continental (Cordilleran) glacier. Because the wet, cold conditions of glaciated regions are relatively intact here, these boreal meadow complexes represent a disjunct ecological province of unmatched biological diversity. The unusual nature of this boreal province is documented in this report. What is enigmatic is how it has managed to remain intact.

HUMMOCKS

Due to the presence of nearby volcanism combined with the effects of landform shape wrought by glaciation, unusual community types occur here that are largely unknown elsewhere, particularly south of the extent of the Cordilleran ice sheet. Extensive muskeg-like bogs in this area are dotted with regularly-spaced "earth hummocks" (Scotter and Zoltai, Earth Hummocks in the Sunshine Area of the Rocky Mountains, Alberta and British Columbia, Arctic 35:411-416, 1992), which appear to be linked to pleistocene ashfall in permafrost regions.

FIRE

Several types of burn condition are present in Thunder fire. Burn conditions observed for overstory canopies include:
(1) Hot burned overstory areas, which left no visible live trees in 1994, primarily in lodgepole stands.
(2) Scorched areas, with 50% to 90% of the overstory killed, with red needles generally remaining on the trees.

Burn conditions observed for understory vegetation include:
(1) Hot burned understories, which left no visible aboveground vegetation below the trees in 1994, primarily in either lodgepole stands, or shrubby areas.
(2) Understory burns areas, with canopies more than 50% intact, primarily in Douglas fir/pinegrass areas.
(3) Patchy fire mosaics, produced by smouldering fire in grassy meadows.

(4) Scorched wetlands, produced when a hot burning overstory killed wetlands vegetation through radiant and convective heat transfer, without spreading into the area through a ground fire.

The Thunder Mountain fire was neither a devastating nor catastrophic event. There is a tremendous opportunity to learn about natural recovery from fire in this environment. The following pages contain information on some of these processes. Go to the page on
threats to see what is at stake in the Thunder Mountain area.