Natural History of the Ozette Prairies

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Regional Setting: Olympic Peninsula and Lake Ozette

Climate

Hydrology

Vegetation

Endangered Species

Fire History

Environmental History

Regional Setting:  Olympic Peninsula and Lake Ozette

The Olympic Peninsula stands as the western extension of the state of Washington.  It has about 200 km of Pacific Ocean coastline, 200 km of Strait of Juan de Fuca coastline and over 400 km of coastline along Admirality Inlet, Hood Canal and Puget Sound within the Puget Lowlands (regional map).  The Strait of Strait of Juan de Fuca and Pacific coast meet at rocky Cape Flattery, forming the ‘northwestern-most point in the lower 48 States.’ The center of the peninsula contains the Olympic Mountains which rise to elevations over 2200 m.  Most of the mountains are within Olympic National Park.  The park is ringed by foothills that are both National Forest and private land, which has been subjected to intensive logging.  The western slope of the mountains are dissected by deep, linear valleys that are oriented SW-NE.  The intervening mountain ridges widen towards the coast into hilly country mostly below 300 m.

The Ozette region is located on the remote northwestern coast of the Olympic Peninsula, in Clallam County, WA, approximately 190 km northwest of the metropolitan hub of Seattle (see map).  The Makah Tribe, who had a village at Cape Alava about 30 km south of Cape Flattery, originally called the region Osette.  Today, an island, Indian Reservation, town site, Makah village site, ranger station, river and lake all share the Ozette name.  Lake Ozette is located approximately 2 to 4 km inland of the Pacific Ocean.  Owing to its location near the Pacific, the climate and vegetation of the region have a strong marine influence.  [Top of Page]

Lake Ozette Basin

The 29.5 km² (2,954 ha) Lake Ozette is the third largest natural lake in Washington (see map). The lake lies 29 feet (~9 m) above sea level.  Lake Ozette is classified as a large, monomictic, oligotrophic to mesotrophic lake, averaging 40 m deep (Bortleson and Dion 1979, Beauchamp et al. 1995, Jacobs et al. 1996).   Lake Ozette drains an area of more than 200 km² (see map).  The topography of the basin is steep, with peaks rising 70 to 100 m as close as 0.3 km of the lake shore, and the maximum elevation in the watershed is approximately 580 m above sea level.  Three perennial tributaries along the eastern and northeastern portions of the lake account for ~58% of the drainage into the lake. The only access to the lake is via the Hoko-Ozette road to the north shore (see map).

The land use surrounding Lake Ozette is indicative of land use throughout the Olympic Peninsula.  The Makah Tribe and other native peoples practiced a hunter-gatherer type of subsistence lifestyle in the region for thousands of years (McMillan 1999).  European homesteaders first began to locally clear forests in the late-1800s.  Commercial logging did not begin until the 1940s.  Today, approximately 23% of the watershed—in addition to the lake and the lake’s shores—is managed as part of Olympic National Park (see map).  Sixty-seven percent of the land surrounding Ozette is privately owned, largely utilized for intensive timber production (Jacobs et al. 1996).  The remaining 10% is State owned, and is also managed primarily for timber production.  Only about a hundred people occupy the watershed year-round.

Climate

The climate of the Ozette region is marine with mild seasons and excessive precipitation.  Under the Köppen system its is west coast marine-  Cfb.  Similar to other coastal regions in the Pacific Northwest, the Olympic Peninsula’s temperatures are moderated by the neighboring Pacific Ocean and are marked by cool mild winters, and warmer, though still mild summers.  The climate of the region is exemplified by data from Forks, WA, located ~30 km to the southwest of Lake Ozette.  Forks experiences a maximum mean of ~16°C during the July to August period, and a minimum mean of ~4°C during the December to January period.  Extreme temperatures are rare.

Although the region experiences moderate temperatures, its precipitation totals are extreme.  The Ozette region is located on the windward side of the Olympic Mountains (see map).  As such, it receives an immense amount of rain due to its position as the first land surface to introduce uplift to the air masses arriving from the Pacific.  Annual surface precipitation in the Ozette region averages an immense 305 cm, 80% of which falls between the months of October and March.  During this period, the Polar Jet Stream migrates into the region, bringing storm after storm.  Heavy rains—amounts exceeding more than 5 cm per day—are occasionally experienced, often times resulting in the flooding of Lake Ozette and its tributaries (Jacobs et al. 1996).  Snowfall is rare due to the mild winters. The influences of the Pacific Decadal Oscillation, La Niña and El Niño can be detected in precipitation records, but extremely wet or dry years are infrequent due to the high precipitation totals.

The combination of mild temperatures and high precipitation results in rainforest conditions in areas surrounding Ozette.  Dew and fog deposition are significant when it does not rain.  Advection fog continually forms off the coast, and can drift inland at anytime.  The continually clouded or fogged skies of the Ozette region result in an average of less than 1,800 hours/year of sunshine, thus earning the region the title of  ‘location in the United States that receives the least amount of sunshine’ (Gustavson et al. 1997).

Prevailing winds arrive at the Olympic Peninsula from the southwest (see map). The wind velocity is typically strong due to the proximity to the coast and low, rolling topography. Strong windstorms and gusts in excess of 30 mph occur several times each winter in association with low pressure systems.  These winds commonly topple trees. Over the Lake Ozette basin winds are funneled northward.  With the long fetch across the lake, the wave environment at the north end of the lake is vigorous, with 30-50 cm high waves common.

The prevailing southwesterly winds are deflected to the north and south through topographic lows. Deflected winds can have higher velocities as their streamlines are compressed. To the north of the Olympics where wind is also deflected south from the Vancouver Island Ranges, these winds converge into a topographic funnel of the Strait of Juan de Fuca, resulting in much higher wind speeds.  Winds that blow over the mountains are slowed and funneled into the NE-SW oriented valleys on the western slope of the mountains (see map). In the continental United States, the heaviest precipitation occurs at the Hoh Rain Forest on the western side of the Olympic Mountains in Washington, where an average of 3,800 mm (150 in.) or more is received annually as storms are funneled up valleys oriented towards winter storm tracks. Atmospheric-pressure conditions determine whether the air, after passing over a mountain barrier, will maintain its altitude or whether it will be forced to descend. If the air is forced to descend, it will be heated by compression (adiabatic heating) and will result in clear, dry conditions and the rainshadow effect. This is a characteristic phenomenon in the lee of mountains and is responsible for the famous Foehn or Chinook winds. In the Olympic Mountains, precipitation decreases from the windward side to less than 430 mm (17 in.) at the town of Sequim on the leeward, a distance of only 48 km (30 mi.).  The winds also converge in the lee of the Olympics, as they are blocked and by the Cascades, creating the ‘Puget Sound Convergence Zone,’ an area of localized increased precipitation.   [Top of Climate] [Top of Page]

Hydrology of the Ozette Watershed

The natural hydrologic regime on slopes within the basin is very responsive to precipitation.  Steep slopes and high soil moisture content (due to high precipitation totals) leads to high overland flow. Since all points within the drainage are within about 8 km of the lake (except the 21-km long Big River drainage), this overland flow is delivered to the lake simultaneously by all drainages within a few hours of the onset of precipitation.  Because of its single outlet, the lake-level can rise and fall 2 meters during a precipitation event, much like a large river does during a flood event.  The lake level also fluctuates seasonally with the precipitation regime.  The fluctuations are exacerbated by clear-cut logging.

The removal of vegetation by logging decreases the interception rate by the canopy, thus increasing the delivery rate of precipitation to the soil surface.  Since the soil moisture content is typically high, this translates to a higher rate of overland flow than with the forested surface and more water than natural conditions delivered to the lake.  Thus lake levels are expected to be lower during the precipitation season in the pre-logging era than the post-logging era.  Since less precipitation infiltrates the soil on a logged parcel and evaporation rates are increased due to less shading of the soil by the canopy, the recharge of groundwater is decreased.  Over time (decades to centuries), the lower rate of groundwater recharge will lower the transmission rate of groundwater, and smaller quantities will be discharged into the lake.  The lower rates of groundwater discharge will be most substantial during the drier summer season when groundwater discharge constitutes a larger input of water to the lake.  Thus, lake levels are expected to be lower during the low-precipitation season in the post-logging era than in the pre-logging era.  The overall impact of logging on the hydrology of Lake Ozette is expected to be an increase in seasonal lake-level fluctuation:  higher winter-season levels and lower summer-season level.   [Top of Page]

Vegetation

The Ozette region boasts a highly productive and diverse vegetative ecosystem.  There are several different vegetation communities in the area.  Here we will describe the five common communities in and around the Ozette Prairies: forest, edge-effect forest, prairie upland, Sphagnum bog and sedge fen.  Among the communities not described are riparian, lake shore, forest wetland, clear-cut logged, coastal shore, and coastal fog zones.  It should be noted that many these vegetation communities exist in a fairly ‘natural’ state.  This can be said for the area west of Lake Ozette and the Ozette River which has never been connected to the rest of the peninsula by road, and has never been commercially logged.  Thus, the major disturbances to vegetation communities that have occurred elsewhere on the Olympic Peninsula have not befallen this area.  However, millennia of human use by indigenous people, 50 years of homesteader use during the first half of the last century (including logging by hand and sheep grazing), and recreation use during the last half century, have all contributed to impacts to the vegetation.

Forests

               The forest community surrounding the Ozette Prairies has been described as a Sitka Spruce forest (Agee, 1993), coastal forest, or temperate (or Olympic) rainforest (Cooper, 1957, Franklin & Dyrness 1973).  The long growing season and humid condition leads to very luxurious forest growth.  Pacific fog, which can extend inland to an elevation of about 300 m, is an important component in creating this community.  A distinctly different community, with a similar species composition, occurs within ~200 m of the coast.  There, the trees are deformed, especially twisted and buttressed by the effects of sand and salt spray (Huesser, 1960).  The forest to the west of the lake and river has never been commercially logged, only small areas were cut by homesteaders.  Thus, the forest can be considered to be old-growth.  Where logged, to the east of the lake, the forest is replaced principally by red alder and Douglas fir.

 A thick cover of tree species growing 20-50 m tall dominates the forest vegetation, creating a dense canopy that allows very little sunlight to reach the forest floor. Four tree species dominate in the forest, Western Hemlock, Sitka Spruce, Western Red Cedar, and Yellow Cedar.  All four can grow to magnificent sizes, 4 m+ in diameter and over 60 m high.  Such large individuals, however, occur infrequently in this old-growth forest.  Shallow water tables, impervious iron pans, and nutrient deficiencies at depth restrict the trees to a shallow rooting depth.  The shallow rooting habit combined with regular strong winds, results in frequent blow-down of large individuals.  The forest floor is littered with downed trees. 

Shade-tolerant species and the abundant leaf, branch, and trunk litter produced by trees dominate the forest floor.  The undergrowth consists largely of Salal, Deer Fern, and Evergreen Huckleberry, locally concentrated into impenetrable thickets.  Several other species occur on the forest floor including Pacific Yew, Cascara, and Red Huckleberry.  Riparian and wetlands occur in depressions with their own suite of hydric species including Skunk Cabbage and sedges.  Nearly every surface is coated with mosses or liverworts.  [Top of Vegetation] [Top of Page]

Edge-Effect Forest

The boundary between the forest and the prairies are obvious from the prairies and from aerial photographs.   From the prairies the forest edge appears as a wall of mature trees.  Occasionally there is an invasion of young trees from the forest edge into the prairie, but more often the shrub vegetation continues to the base of the large trees.  From the prairie edge, extending 10-30 m into the forest is the ‘edge-effect’ forest.  In this zone, the vegetation is dramatically responding to the sunlight that enters the forest floor from the adjacent prairie opening.   The density of understory shrubs and young trees is much higher than inside the forests, typically forming an impenetrable thicket.  The shrubs grow several times larger than in the forest understory.  Branches from the older trees near the forest edge stretch towards the sunlight of the prairie.  The edge effect growth seems better developed on the east-sides of the prairies compared with the west-sides, since the east-sides get the warmer afternoon sunlight.

Salal is especially thick and large along these edges.  Pacific Crab Apple and Red Huckleberry are more common along the edges.  A few Pacific Yew were noted along the edge, but they may have only been easier to identify since the needles were closer to the ground than inside the forest.   [Top of Vegetation] [Top of Page]

Prairie Upland

We did not closely investigate the vegetation composition of the prairies, but we did note several different communities which will be broken into three groups here:  sedge fens and Sphagnum bogs over wetlands, and prairie uplands on the mineral soils.  The mineral soils tend to be on slopes >2° surrounding the wetlands.  There are several variations in species composition in the Prairie Upland, but the defining composition is that of ~0.5 m high densely spaced woody shrubs and tree saplings, with few sedges and grasses, many young trees 1-10 m high, and a thick understory of herbs, fern, lichen and mosses. Based on our soil analysis and the presence of many burnt stumps and snags in this zone, we believe that this vegetation community is a successional stage following the expansion of the prairies into the forest by burning.

By far and away the two most common woody shrubs are Labrador Tea and Bog Laurel.  Salal is locally abundant especially near the prairie edge, but is often short.  Western Hemlock, Sitka Spruce, and Yellow Cedar saplings and young trees are very common on the uplands.  Cedars saplings are the most common, closely followed by hemlock, with fewer spruce.  The trees on the prairies occasionally occur as individuals, but most commonly occur in high density ‘tree islands.’  Most these trees have a yellow hue to their needles, likely resulting from nutrient deficiencies.  A few larger, older individual trees, mostly hemlock, also occur in the Prairie Upland.  Annually, Bracken Fern grows up and over the shrubs, dying in early fall and producing a thatch.  Less common shrub species include Evergreen and Bog Blueberry, stunted Deer Fern, and Crow Berry.  There are several small wetlands in depressions and drainages on the Prairie Uplands.   [Top of Vegetation] [Top of Page]

Sphagnum Bog

                The northern side of Roose’s Prairie, the unnamed prairie along the Cape Alava trail to the west of Ahlstrom’s and scattered elsewhere are raised Sphagnum Bogs.  These wetlands are dominated by the growth of sphagnum mosses, which have accumulated into peat.  The mosses grow into mounds up to 0.5 m above the general ground surface, engulfing woody vegetation.  Most commonly the woody vegetation is Crow Berry, but Labrador Tea, Bog Laurel, Salal, and Yellow Cedar are common in the bogs as well.  The trees growing in the bogs are very yellowish and quite gnarled, likely resulting from nutrient deficiencies.  The nutrient deficiencies are a result of the highly acidic nature of theses bogs.  Shrubs and trees are less common than on the Uplands, allowing more sedges and herbs to occur.  Most unique is the carnivorous Sun Dew.  Others plants include, but by no means are limited to Bog Cranberry, Sticky False Asphodel, Several-Flowered Sedge, Swamp Gentian, King Gentian, and Great Burnet.  Standing water is rare in these wetlands, but the watertable typically lies just below the surface.  Numerous snags, some burnt, many just small dead trees, are scattered across these bogs, giving them a ghostly look.   [Top of Vegetation] [Top of Page]

Sedge Fen

               Central Ahlstrom’s Prairie and other small wetlands scattered around the prairies are sedge dominated fens.  These fens appear as tall fields of grass, and are likely responsible for these openings being called prairies.  Fens occur where there is a slight slope and some drainage occurs in the wetland, creating a less acidic environment.  Small, deep streams trickle across these fens.  While the surface has moss, it does not grow into mounds.  Rather, a variety of sedges, reeds and grasses are the dominate vegetation type, with some herbs.  Most common is the Slough Sedge.  Chamisso’s Cotton Grass with its white tufted tops are very noticeable. Others plants include, but by no means are limited to Bog Cranberry, Sticky False Asphodel, Several-Flowered Sedge, Swamp Gentian, King Gentian, and Great Burnet.  Trees and woody shrubs are rare on the fens, although they do differ from the bogs in that there is a distinct zone of Bog Laurel/Labrador Tea growing along their edges.  [Top of Vegetation] [Top of Page]

Endangered Species

Butterflies:  Makah Copper and Ozette Skipper

Male Makah Copper

Female Makah Copper

Mating Makah Coppers

The coastal rainforest of the Olympic Peninsula is among the most impoverished butterfly habitats in the world (Pyle, 2002).   This is a consequence of the unique geographic setting creating isolation from suitable butterfly habitats: surrounded by ocean to the north and west, high-elevation tundra to the east, and lush forest vegetation to the south and throughout.  Additionally, the large number of rain days means few opportunities for butterfly flight.  Many of the natural open wetlands (prairies) in the Ozette region are found to be habitat for butterflies, providing a larger number of flowers than the rainforest environment.

Pyle (2002) through field observations has identified two species of butterflies which are distinct enough to possibly represent new taxon.  The Makah Copper is a variation of the Mariposa Copper (Lycaena mariposa). These butterflies are ~3 cm across.  Males are copper colored above, females are yellow-orange with heavy black spots and borders, and both have black and white checked fringes.  Bottoms of wings are tan to gray with black dots and dashes.  Makah Coppers are known to feed upon Swamp Gentian, whose bloom peaks with the butterfly’s flight period.  The Makah Copper is a candidate species for the Washington State Endangered Species list, and is a Federal Species of Concern (Pyle, 2002).  The Ozette Skipper is a variation of the Woodland Skipper (Ochlodes sylvannoides).  These butterflies are 2-3 cm across, and composed of blotchy patterns of yellow, orange and tan.

The populations of these butterfly species are small, and very fragile.  They rely upon the vegetation that grows only on the few prairies in this region.  It is unlikely that they can migrate to any other suitable habitat.  Please do not attempt to capture. [Top of Page]

The Sockeye Salmon of Lake Ozette

Throughout the nation, salmon populations have been dwindling at an alarming rate, but possibly none so disconcertingly as the population of sockeye salmon (Oncorhynchus nerka) in Lake Ozette, Washington.  Population data from the lake indicate that over the past 60 years, the salmon have declined by an estimated 90-98% (Adkinson and Burgner 1997).  During the early to mid-1900s, the lake supported annual runs of 18,000 to 30,000 sockeye.  However, recent observations suggest that a mere 300 to 2,200 adults return to spawn in the lake, with an average of less than 1,000 annually (Gustavson et al. 1997; Jacobs et al. 1996).  An initial substantial decline in the late 1940s/early 1950s of approximately 15,000 sockeye was followed by lesser, though consistent, declines for several decades.

The National Marine Fisheries Service (NMFS) determined that Lake Ozette sockeye represent an Evolutionary Significant Unit (ESU), and the population is listed as “threatened” as defined by the Endangered Species Act (ESA 1973: Section 3).  Although the population is not presently in danger of extinction, the team concluded that the population is likely to become endangered if present conditions continue into the foreseeable future (Gustafson et al. 1997).  Several conditions in the Ozette watershed are believed to have contributed to the population decline (Table 1).  Though no single factor has been identified, logging may be a significant factor due to its suspected negative impact upon habitat (Bortleson and Dion 1979, Dlugokenski et al. 1981, Blum 1988, Adkinson and Burgner 1996, Geiger 1996, Jacobs et al. 1996, Lestelle 1996). Approximately 85% of the watershed has been clear-cut logged during the past 80 years (Bortelson and Dion 1979, Blum 1988).  The historical and current impacts of logging may have disrupted the natural hydrology, disturbing spawning grounds (Blum 1988, Geiger 1996, Jacobs et al. 1996, Lestelle 1996).  We have investigated both the impacts of hydrologic changes and soil erosion caused by logging.

Though Lake Ozette sockeye’s spawning practices and life cycle do, in general, follow the typical behavior of sockeye salmon, they do exhibit some unique adaptations (Gustafson et al. 1997).  Similar to most sockeye, Ozette sockeye choose spawning sites based on water flow and gravel size.  Spawning is concentrated along lake shores at a 0.3 to 2.8 m range of depth, with a majority of redds placed between 1.0 to 2.8 m in depth.   The eggs (and alevins) are extremely sensitive to water depth: in too low of levels of water the eggs are desiccated, and in too high of levels the eggs receive too little aeration to survive (Bortleson and Dion 1979, Jacobs et al. 1996).  The spawning routine occurs between November and March (see figure).  The eggs incubate for 68 to 82 days, a period less than the average incubation period for sockeye (Jacobs et al. 1996).  During April to June, the juveniles emerge and migrate to the pelagic zone of the lake where they rear for approximately one year before undergoing smoltification and emigration to the ocean in April and May (Jacobs et al. 1996).

Fire History

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Environmental History

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