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ALASKA INTERIM LAND COVER MAPPING PROGRAM (USGS)

STATEWIDE INTERIM LAND COVER MAP

Land use/land cover data were produced for a number of project areas in Alaska. These data were cross-walked to the Alaska Interim Land Cover Mapping Program land cover classes (U.S.G.S., 1987; Shasby and Carneggie 1986; Fitzpatrick-Lins and others 1989). Each individual land cover map was resampled to a 1-km pixel and projected into the Alaska Albers Equal-Area Conic projection. Projection parameters for the data set is shown in Table 1. Class values are shown in Table 2 followed by class descriptions.

Table 1 Projection parameters for the interim statewide land cover data set.


Albers Equal-Area Conic

First standard parallel 55 00 00 N

Second standard parallel 65 00 00 N

Longitude of central meridian -154 00 00 W

Latitude of origin 50 00 00 N

False easting 0

False northing 0

Units of measure Meters

Pixel size 1,000 meters

For Alaska

Center of pixel (1,1) ( -977000, 2422000 )

Number of lines 1,992

Number of samples 2,512

Albers meters for minimum bounding rectangle:

Lower Left ( -977000, 431000 )

Upper Left ( -977000, 2422000 )

Upper Right ( 1534000, 2422000 )

Lower Right ( 1534000, 431000 )

Geographic decimal degrees:

< Lower Left ( -168.5970, 52.9222 )

Upper Left ( -179.8476 70.0416 )

Upper Right ( -116.0057 67.6962 )

Lower Right ( -131.5953 51.5372 )

Geographic degrees, minutes, and seconds:

Lower Left ( -168 35' 49" 52 55' 20" )

Upper Left ( -179 50' 51" 70 02' 30" )

Upper Right ( -116 00' 21" 67 41' 46" )

Lower Right ( -131 35' 43" 67 32' 14" )


Table 2 Class values and class names used for the interim land cover class map.

Class # Class Name

1 Closed needleleaf forest

2 Closed broadleaf forest

3 Closed mixed needleleaf/broadleaf forest

4 Tall and low shrub land

5 Dwaf shrub and related communities

6 Dry or moist herbaceous

<7 Wet herbaceous

8 Aquatic herbaceous

9 Mosses

10 Lichens

11 Agriculture

12 Urban land

13 Sparsely vegetated

14 Non-vegetated

15 Clear and/or deep water

16 Turbid and/or shallow water

17 Ice, snow, and clouds

18 Shadow

Not all classes occur within each data set

CLASS DESCRIPTIONS

Needleleaf Forest (class 1)

Needleleaf forest types are composed of two sub-classes, closed needleleaf forest and open needleleaf forest.

Closed Needleleaf

Closed needleleaf forests are dominated by white spruce (Picea glauca) on well drained sites and along drainages, or black spruce (P. mariana) on lowland sites over much of Alaska. Larix laricina also occurs in small stands in central Alaska. In southeast Alaska, forests are dominated on a variety of sites, slopes, and aspects by Sitka spruce (P. sitchensis) and hemlock (Tsuga heterophylla and T. mertensiana) with Alaska-cedar (Chamaecyparis nootkatensis). Crown closure follows that of Viereck and others (1992) at 60 to 100 percent, although some of the land cover project data used to produce the Statewide land cover map were based on slightly different criteria to define closed canopy (e.g., a 75 percent cut-off instead of 60 percent). Under story layers may consist of Alnus sp., Salix sp., Betula glandulosa, Spirea beauverdiana, Ledum palustre, Arctostaphylos uva-ursi, Vaccinium sp., Menziesia ferruginea, Oplopanax horridus, Ribes sp., and various species of moss (particularly of the genus Sphagnum and Hylocomium sp.).

Open Needleleaf Forest

This class is similar to the closed needleleaf forest with the major difference being crown closure is 25 to 59 percent. Under story vegetation is also similar, except that shrub and forb/graminoid density may be considerably higher and of a more diverse nature than in the closed needleleaf forest.

Broadleaf Forest (class 2)

As with the needleleaf forest, there are two sub-classes of broadleaf forest, closed and open.

Closed Broadleaf Forest

Broadleaf forest types occur throughout Alaska south of the Brooks Range, although a few small stands may occur in arctic areas (e.g., in the Sadlerochit Mountains and central Noatak River valley). Crown closure is 60 to 100 percent. Common overstory species include Populus trichocarpa in southeast Alaska, and in some cases Alnus rubra. However, for the majority of the State, P. balsamifera, P. tremuloides, and Betula papyrifera are the dominant species. Understory vegetation is highly variable in species composition and density dependent on overstory type, location, and crown closure. Alnus and Salix are the more common shrubs present, although Spirea beauverdiana, Ledum groenlandicum,, Vaccinium sp., and Menziesia ferruginea may occur on moist sites, and Vaccinium sp., Rosa acicularis, Arctostaphylos uva-ursi, Shepherdia canadensis, and Viburnum edule on dryer sites. A variety of forbs may be present, some of the more common include: Calamagrostis canadensis, Equisetum sp., and Epilobium sp. A few common cryptogams include species of Polytrichum, Drepanocladus, and Hylocomium.

Open Broadleaf Forest

Open broadleaf forests have crown closures of 25 to 59 percent and are composed of the same species as the closed broadleaf forests. The understory nature of these forests are highly diverse in terms of species and cover. As crown closure opens, understory species are much more prominent, and may form a secondary closed, understory canopy (up to 100 percent on some alluvial sites), commonly of Alnus and/or Salix, with a tertiary sward of Calamagrostis sp. On more upland sites, the understory may be dense, often times lush, and composed of Calamagrostis sp, Epilobium sp., Galium boreale, and Equisetum sp.

Mixed Forest (class 3)

This class is composed mainly of closed forest canopies, having crown closures of 60 to 100 percent and are composed of both needleleaf and deciduous species, although no one leaf type dominates. Species makeup are similar to the other forested classes for tree, shrub, forest floor species, and occur throughout the State south of the Brooks Range. Species cover is highly dependent on overstory crown closure, overstory species makeup and age, and site.

Tall and Low Shrub (class 4)

There are two sub-classes for tall and low shrub lands, closed and open.

Tall and Low Shrub - Closed

This type occurs primarily on upper hill slopes, mid mountain slopes, or along rivers, streams, and small wet or water-logged basins . It also may be found on mid- to upper- elevation slopes in the northern portions of the State in combination with shrubby tundras. Shrub canopy is 75 percent or greater with heights ranging from 20 cm to over 1.5 m. For the Statewide map, canopy cover may vary from 60 - 80 percent depending on location and original project data used. Alders (Alnus sp.) and willows (Salix sp.) are the more common species present, although shrubby birches (Betula glandulosa), Myrica gale, or Chamaedaphne calyculata also may dominant depending on site. Under story vegetation may consist of graminoids (Carex sp., Calamagrostis canadensis), forbs (Petasites sp., Epilobium sp.), and a variety of mosses and lichens depending on canopy closure and site. In many northern areas, this type also may represent sites that contain an open tall alder/willow component, but with a high ground cover of low willow (Salix sp.) and low or dwarf birch (Betula glandulosa or B. nana). In addition to the traditional shrub species, this type may also include small stands or clumps of trees, more commonly B. papyrifera and Populus balsamifera, or P. tricocarpa.

Included with this class are needleleaf woodlands, which extend the conifer forest continuum tomore sparse cover with 10 to 24 percent crown closure. Species mix is similar to the forested classes above and have a higher abundance of shrubs in the under story. In the central and northern boreal areas of the State, a multitude of conditions may occur. Under story vegetation may be dominated by lichens and have few shrub or forb species present, or there may be a high percent cover of deciduous and/or evergreen shrubs depending on site and aspect. In lowland or forest tundra areas this type also may include Betula nana, Petasites frigidus, Empetrum nigrum, Rubus chamaemorus, Vaccinium vitis-idaea, and Carex bigelowii, to name a few. In southeast Alaska, these types may have a high density of tall Alnus or Salix species, or may be represented by Sphagnum sp. dominated shrubby bogs.

Tall and Low Shrub - Open

This class is similar to the tall and low shrub - closed class except that shrub cover is generally less than 75 percent.. Stands of open alder or small clumps of willow may be found on a variety of mountains slopes and elevations (depending on latitude), upper slopes of rounded hills and on steep mid slopes of hills. In the northern portions of the State, an under story of Betula sp and a number of low growing deciduous and evergreen species (Vaccinium, Empetrum, Ledum) are common. A variety of graminoid and forb species may be present, including Carex sp., Eriophorum sp., Equisetum sp., and Petasites sp.

Dwarf Shrub and Related Communities (class 5)

This type is generally recognized as having few plants greater than 20 cm high and are dominated by dwarf birch and a variety of ericaceous species. In the boreal and northern forest limit areas, dwarf birch (Betula glandulosa and B. nana) and dwarf ericaceous like shrubs are commonly found (Cassiope tetragona, Arctostaphylos uva-ursi, Vaccinium uliginosum, V. vitis-idaea, Ledum decumbens, Dryas integrifolia, D. octopetala, Rubus chamaemorus and Salix sp). This type is also found in tundra communities and is common on upper slopes of mountains, as well as peatland communities. Mosses (primarily Sphagnum sp.) are common in peatland types, however, lichens (Stereocaulon sp., Thamnolia sp., as well as other fruiticose and crustose species) also may be present.

This class may also consist of communities dominated by lichens, occurring in both mountain and in lowland areas. Dry upper hill and mountain slopes, or other sites prone to windblown conditions may be dominated by a variety of lichens (for example, Cetraria, Thamnolia, Stereocaulen) associated with Dryas sp.

Dry or Moist Herbaceous (class 6)

This type is dominated by sedges (primarily Carex aquatilis and C. bigelowii), normally with greater than 60 percent cover. Most sites have other grass or grass-like plants (Eriophorum sp., Luzula sp., Juncus sp.) as well as scattered shrubs (Salix sp., Arctostaphylos uva-ursi, Dryas sp.) and forbs (Valeriana capitata, Pedicularis sp., Equisetum sp.). In some areas, C. bigelowii or Eriophorum vaginatum may form tussocks. Mosses and lichens also may be present in varying amounts in the under story. Tussock areas can occur on a variety of sites and slopes; however, they are commonly found on well-drained hill slopes, in low broad basins, and on coastal plain tundras. Site moisture is subjective but generally without standing water. Some sites will have standing water throughout the spring thaw, but will become dryer as the summer progresses.

Wet Herbaceous (class 7)

This type is similar to the grassland class in species composition but is generally found in areas that contain soils that are moist to saturated throughout the season. Common species include members of the genus Arctophila, Calamagrostis, Carex, Eleocharis, Eriophorum,, Menyanthes, and Scirpus. This class found primarily in low basins throughout the State, tidal areas, and tundra areas where water has been impounded.

Very Wet Aquatic (class 8)

Aquatic wetlands are areas that have vegetation growing in shallow to deep water. This type is common in flooded areas and along pond and lake shorelines. Species will include members of the genus Carex, Scirpus, as well as Arctophila fulva, depending location and soils. Hippuris vulgaris, Nuphar sp., Nymphaea tetragona, Potamogeton sp., and Potentilla palustris also may be present in varying amounts.

Moss (class 9)

Very few moss dominated areas are present in Alaska that can be mapped at a 1 km scale. Those few areas that can are dominated by the species Sphagnum (such as S. fuscum, S. balticum and perhaps Mylia anomala), and are found in west center Alaska. Often, other species occur in these areas such as dwarf shrubs (Chamaedaphne calyculata, Ledum decumbens, Oxycoccus microcarpus, Vaccinium vitis-idaea, Andromeda polifolia, and Empetrum nigrum), graminoids (Carex sp., Eriophorum sp.), forbs (Drosera rotundifolia, D. anglica) and occassionally some lichens depending on site (Cladina sp., Icmadophila sp.).

Lichen (class 10)

Lichen dominated areas are common in Alaska, some of which cover extensive areas, and most of which are associated with a number of low and dwarf shrubs. The most common lichens include Cladina and Cladonia, along with Alectoria and Stereocaulon. Many of the low and dwarf shrubs mentioned previously also may be present, although with less than 20 percent ground cover.

Agriculture (class 11)

This class is small in Alaska and occurs primarily in south central (Palmer), north central (Fairbanks), and east central (Delta Junction) Alaska. Areas are normally small and include hay and grazing fields, and grain fields (primarily oats and barely). Some areas that were actively farmed in the early to mid 1980's have since been abandoned and reverted to Betula papyrifera , Populus tremuloides or P. balsamifera.

Urban (class 12)

This class is also fairly small in Alaska and includes small communities, primarily along major highways and some coastal areas.

Sparsely Vegetation (class 13)

Areas that have more than 5 percent, but less than 25 percent vascular plant cover are mapped as sparse vegetation. Sites may include mountain or ridge tops, rounded or steep talus slopes, or fluvial gravel and sand bars. Vascular plants present in mountainous areas may include Silene acaulis, Diapensia sp., Cassiope tetragona, Rhododendron camtschaticum, Vaccinium uliginosum, Salix sp., Dryas octopetala, Arctostaphylos rubra, and Oxytropis sp. Fluvial areas may contain Epilobium angustifolium, and species of Dryas, Draba, and Carex. Crustose and fruiticose lichens (Cladina sp., Cladonia sp.) may be present in the mountainous areas and on talus slopes as small patches.

Barren (class 14)

Barren areas consist primarily of sand, gravel, rocks, and boulders of various sizes often associated with active flood plains, hill summits, and mountain tops. Vascular plant cover is normally less than 5 percent; however, varying amounts of crustose lichens may be present.

Clear Water (class 15)

This class includes lakes, ponds, rivers, and offshore water bodies with little to no particulate matter.

Turbid Water (class 16)

Turbid water comprises lakes, ponds, rivers, and offshore water that have a high degree of particulate matter.

Cloud/Snow/Ice (class17)

This type consists primarily of bright reflective surfaces that are common with snow, ice (glaciers, overflow ice, ocean and lake ice), and various amounts and types of cloud cover.

Shadow (class 21)

The shadow class represents those areas obscured from remote sensors by mountainous terrain (for example, steep north-facing slopes). Vegetation may or may not occur in these areas depending on a combination of latitude, slope, aspect, and elevation.


LITERATURE CITED

Fitzpatrick-Lins, K., Doughty, E.F., Shasby, M., and Benjamin, S., 1989. Alaska Interim Land Cover Mapping Program - Final Report, U.S. Geological Survey Open-File Report 89-128, Reston, Virginia.

Shasby, M., and Carneggie, D., 1986. Vegetation and terrain mapping in Alaska using Landsat MSS and digital terrain data, Photogrammetric Engineering and Remote Sensing 52:779-786.

U.S. Geological Survey, 1987. Alaska Interim Land Cover Mapping Program, Data Users Guide 7, National Mapping Program, Technical Instructions, Reston, Virginia.

Viereck, L.A.,Dyrness, C.T., Batten, A.R., and Wenzlick,K.J., 1992, The Alaska Vegetation Classification,U.S. Forest Service, Pacific Northwest Research Station, General Technical Report PNW-GTR-286, 278 p.


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