Little is known about the flora, fauna, and significant natural features of the Central Mixedwood Subregion of the Boreal Forest Region of north-central Alberta. The complexity of natural environments is a major challenge to ecologists attempting to understand them, particularly the dynamics of change at both the local and landscape/ ecosystem levels. In the 11km2
Crooked Lake Study Area, vegetation types and associations (their species
composition, age, and extent) are extremely diverse and form a mosaic in which old-growth stands predominate.
This diversity is due less to disturbances such as wildfire, and more to glacial origins: topography, soils, wetland distribution, hydrology, and microclimate variability, together with intervals of beaver and ungulate influences. To date,
a total of 309 native vascular plant species (clubmosses, horsetails, ferns, trees, shrubs, and herbs) and only 13 introduced (non-native) species have been identified. Approximately 56 non-vasculars (lichens, liverworts, mosses,
and algae) have been recorded, although a complete survey of this group was not feasible. To date, a number of rare, edge of range, hybrid, and otherwise scientifically significant plants have been recorded, as well as one rare plant
association. The survey includes 233 vertebrate species: 35 mammals, 190 birds (of which 116 nest), 3 amphibians, and 5 fish. Significant ecological features, many of regional or provincial importance, are described and
recommendations for further studies are listed.
CROOKED LAKE BIOPHYSICAL SURVEY 2000
Canada’s Boreal Forest is now being recognized as a vitally important and very complex ecosystem; its integrity is of critical value to the perpetuation of Canada’s wildlands and their dependent wildlife. The Central Mixedwood Boreal Subregion of Alberta is experiencing increased northward development, especially of timber and petroleum resources, agricultural expansion, and a variety of recreational/ residential activities.
Due to the present limited ecological information about the flora, fauna and
significant natural features of the region, it is important to identify and document, as soon as possible, the values of areas of particular interest as well as effective linking corridors. The Crooked Lake Biophysical Survey was undertaken to assess the ecological and natural features of an 11 km² Study Area (approximately 40 km northwest of the Town of Athabasca) on provincial crown land where initial reconnaissance had indicated the potential for high biodiversity and varied terrain. The most intensive fieldwork was completed in 2000, with additional information obtained from 2001 through 2004. Due to time and personnel constraints the survey focused on vertebrates, vegetation associations, and vascular plant species, at site and landscape scales, together with preliminary ecodynamics in the context of the past 200 years.
Ecoclimatic classification places Crooked Lake (54°55’ N, 113° 33’ W; 620 m asl) within the subhumid low boreal ecoclimatic region with an average annual precipitation of 464 mm rain equivalent (usually highest from May through August). The long summer days can be hot, but clear nights cool rapidly; while winter extremes in January can drop to –45°C. Average winter snowfall is 150 cm, with snow cover usually from early November to late April. Except in convective and frontal storms, prevailing winds are usually light
W–NNW, with S–SW winds more frequent in summer.
Crooked Lake’s watershed comprises 182 km² of rugged glaciated terrain that includes several small lakes and three other medium to large lakes linked to Crooked Lake by permanent streams, while Crooked Lake’s own outlet is a meandering stream, of ecological merit, that flows into the Athabasca
River. Crooked Lake was originally formed as a large glacial meltwater channel cut along the edge of a high, ravined hummocky moraine, and a lower almost level ground moraine. A second lake within the Study Area is a small, permanent, basin headwater lake that partly outlets into Crooked Lake along a
channel treed fen.
Presently disturbed areas in the Study Area cover only 17 ha, the remainder being roadless native vegetation. A total of 21 native vegetation types and 44 plant associations/subassociations were identified and described. The forest cover of 681 ha includes poplar, mixedwood, and conifer, with mixedwood the
most extensive type (377 ha). Old-growth forest (live tree age ≥ 80 years) of all types, including treed fens, covers 560 ha, which is 82% of the total forested area. Other old-growth vegetation includes some willow and graminoid fens, rooted aquatic associations, and two quagmires. The high proportion of oldgrowth vegetation in both extent and diversity of types is very unusual. Additionally, in a variety of both mature and old-growth forest types, fir, Abies, ranging from seedlings to live old-trees and deadfall, and occurring at ≥30% cover, totals 93 ha. The fir appears to be an introgressed population of Abies bifolia and A. balsamea, as occurs at much higher elevation in the nearby Swan Hills and Pelican Mountain.
One vegetation type, open quagmire with Scheuchzeria, has been formally recorded as a Rare Plant Community (Carex limosa–Scheuchzeria palustris/Spagnum teres–S.subsecundum) by the Alberta Natural Heritage Information Centre. A total of 309 native vascular plant species plus 13 introduced species (most on disturbed ground) has been documented, including several species of as yet unclear taxonomic status. Ten provincially recognized rare species (including two mosses, and the rarest Alberta
orchid) were recorded, and an additional 17 species that are near the limits of their range, otherwise noteworthy, or sensitive to habitat change. Most of the rare/unusual plants occur in old-growth vegetation.
The only major disturbance to the vegetation during the past 200 years seems to have been an extensive wildfire estimated to have occurred in the mid-1800s. A much smaller fire (146 ha) in 1948 and mainly affecting upland forest, has regenerated to primarily mature poplar-dominant Mixedwood Forest, and as such provides insight into post-fire regeneration sequences in the Study Area. The oldest live tree of determined age was a black spruce of 170 years.
The survey recorded 233 vertebrate species: 35 mammals, 190 birds (116 of which nest), 3 amphibians and 5 fish. Although not part of the main survey, collection of several wingless crane flies in late winter 2004, provided a range extension for Chionea alexandriana Garrett. The Study Area’s high faunal
diversity reflects its habitat diversity as well as the relatively unmodified landscape and vegetation of the watershed. The mammal list is expected to increase with more intensive surveys of small species such as bats, shrews and voles/mice. Species that occur as individuals or populations in the Study Area, but whose status is of concern due to habitat change and/or abundance include: northern flying squirrel, wolverine, fisher, cougar, and Canada lynx. Others of particular interest are: water shrew, least weasel, jumping mouse, and northern bog lemming. Of the breeding birds in the Study Area, 64 species require old-growth forest for the nest site, while 54 of these also do most or all of their foraging there. Twenty-five of the nesting species are formally designated rare, sensitive to disturbance/habitat change, or are
showing general population decline.
Of the 3 amphibians, the western toad, Bufo boreas (a species of conservation concern), and the wood frog, Rana sylvatica, are abundant and widespread. One fish, the brook stickleback, Culaea inconstans, is an addition to previously recorded species. A number of significant features (most of regional or provincial importance) are described: several distinctive glacial/post-glacial landscape features that are related to the complex hydrology and soils;
extensive and diverse old-growth vegetation; diverse fen wetlands; four distinct ecologically integrated landscape and vegetation complexes and associated fauna; high biodiversity among vascular plants (including rare species and those of taxonomic interest); a provincially rare plant community, open quagmire with Scheuchzeria; 56 vertebrate species (5 mammals, 50 birds and 1 amphibian) formally designated as sensitive/vulnerable/of special concern. Reconnaissance of crown land along Crooked Creek in 2003–2004 revealed significant landscape, vegetation and faunal features not represented in the Study Area.
The initial survey of the Crooked Lake area has revealed an area of considerable scientific and conservation value, and one where further research would create a reference database of ecological dynamics at the ecosystem level for the Central Mixedwood Boreal in a relatively small but complex area of high biodiversity.