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Shrub/Grass

Maps and Photos of shrub/grass range type
 

Shrub/Grass Climatic Overview

The general climate of the shrub/grass range type of Alaska is influenced by both maritime and continental weather patterns. The average annual precipitation varies greatly from location to location, ranging from approximately 270mm (10.6 in.) to well over 700mm (27.6 in.).  Most of the precipitation in this range type is received late in the season, August, September, and October.  Average precipitation in the spring is very low, sometimes less than 10mm (0.4 in.) creating a potential dry season. The temperature can range anywhere from -20°C (-4°F) in the winter months to above 25°C (77°F) in the summer months. The warmest days usually occur between late June and early August, while the coldest days typically occur in December.  A majority of the areas occupied by the grass/shrub were glaciated during the Pleistocene epoch (Western Regional Climate Center).  The grass/shrub range type can be found on terrain varying from marshy lowlands, with poorly drained soils and permafrost, to rolling hills consisting of drier soils.  The accumulation of large amounts of organic matter and discontinuous permafrost are found throughout the grass/shrub range type in Alaska.

Shrub/Grass Soils

In Alaska the soils of the shrub/grass range type are Histic Pergelic Cryoaquepts,  Histic Pergelic Cryofibrists.  “Histic” indicates that the soil is shallow with poorly aerated organic material.  “Pergelic” refers to temperature regime, indicating the presence of permafrost; and “Aquept” means poor drainage.  Pergelc Cryochrepts have a mean annual soil temperature of 0°C (32°F). In all cases the permafrost temperature perennially is at, or below 0°C (Rieger 1983). These soils are under the order of Inceptisols.  Inceptisols form under a variety of climates except aridic conditions. They are cold soils that often have discontinuous or continuous permafrost, depending on the elevation, aspect, and latitude that they are located (USDA et al. 2004).   Organic horizons here are often as thick as one meter, because high moisture contents and cold temperatures slow the rates of decomposition relative to the large accumulated organic matter (USEPA 2004).   Soils within this ecosystem generally originated as laucustrian, colluvial, or glacial till deposits.  Inceptisols include soils that have some subsoil development but lack features of other soil orders (University of Wisconsin-Madison).

Alaska is primarily comprised of sand, silt and gravel.  Clays are not common because they require more chemical weathering than normally occurs in Alaska.  Fine silts and gravels are common due to significant erosion related to braided streams, glacial ice and permafrost.  Discontinuous permafrost is common of the grass/shrub range type found in Alaska. In spaces between tussocks, the combination of permafrost and fine grained soils accounts for high soil moisture and frequent appearance of frost scars (Washburn 1973).

Vegetative Community of the Shrub/Grass Range Type

The shrub/grassland is often found as an ecotone between the wetlands and coniferous forests, located at higher elevations, in South-central Alaska.  In more mountainous areas, the shrub/grassland exists as an ecotone between the forests within the valleys and alpine tundra (Smith and Smith 2001).   Vegetation of the grass/shrub range type consists mainly of graminoid herbaceous and dwarf shrub communities.  Shrubs are well adapted to the low moisture, low soil nutrients, and relatively short growing season of shrub / grasslands.  They withstand these conditions because they have a lower energy investment aboveground than trees, and shrubs can rapidly develop root systems, allowing them to take advantage of water stored in the soil.  Herbaceous communities dominated by tussocks are widespread in the low lying wet areas (Hagenstein and Rickets 2001).  The most common grass species in Alaska’s shrub / grasslands is bluejoint reedgrass (Calamagrotis canadensis).  It can grow to be 16 - 120 cm (6.3 – 47.2 in.) tall, is a thick growing, rhizomatous perennial.  It has a fair amount of energy, but is generally low in protein.  While in better drained areas, such as on rolling hills, sedges (Carex spp.) and dwarfed shrubs, such as crowberry (Empetrum nigrum), bearberry (Arctostaphylos uva-ursi) and lingonberry (Vaccinium vitis-idaea), rank as the dominant cover type.  Open low scrub communities consist of green alder (Alnus crispa) and woolly willow (Salix lanata). Mosses (Drepanocladus spp.) are also usually abundant (University Corporation for Atmospheric Research).  Shrubs and grasses are well adapted to life in moisture and nutrient poor soils and harsh conditions, which are distinctive of many places in Alaska that are in the early stages of succession, such as glacial moraine and braided riverbeds.  The occurrence of wildfire in the grass/shrub land in Alaska does occur but is not as common as in other vegetation types. Unlike many of the rangelands in the lower 48 states, the majority of Alaska’s grass/shrub range type doesn’t experience problems with overuse or over grazing.  Many of these areas support populations of native wildlife such as moose (Alces alces), caribou (Rangifer spp.), bears (Ursus spp.) and other small mammals (Hagenstein and Rickets 2001).

Current Uses of the Shrub/Grass

The shrub/grassland ecosystems of Alaska cover many large and diverse parts of the state.  Like much of Alaska, large portions of the shrub/grasslands are uninhabited by people.  However, large portions of shrub/grasslands are located in South-Central Alaska and the Kenai Peninsula, one of the most populated regions of the state.  Many Native communities are located within shrub/grass rangeland in Southwest Alaska.  Because of its climate, beauty, and economic opportunities one of the foremost current uses of the shrub/grasslands is for homes, businesses, and cities.

Because of its close proximity to Alaska’s population centers, the shrub/grassland is a common recreation area.  There are numerous tourist attractions, amenities, and fishing, hunting, and other guide services located within this range type.  Many people visit the shrub/grasslands to camp, hike, watch wildlife, canoe, kayak and much more!

Not only do people take pleasure in and benefit from the shrub/grassland, but this range type provides habitat for a vast number of birds and mammals.  To a large extent much of this range type is owned by federal agencies, especially the US Fish and Wildlife Service and the National Park Service.  These areas provide superb habitat to scores of plant, fish, mammal, and bird species.  The Yukon Delta National Wildlife Refuge covers 76,890 km² (19 million acres) of Southwest Alaska, and has 170 species of birds each year that migrate from 6 continents; 136 of which nest right there (Alaska Geographic 1981).  Other significant federal lands composed chiefly of shrub/grass rangelands are the Togiak National Wildlife Refuge, Becharof National Wildlife Refuge, Kenai National Wildlife Refuge, Katmai National Park and Preserve, and Lake Clark National Park and Preserve (Alaska Geographic 1981, and USFWS).  Some shrub/grass rangelands are also owned by state agencies or managed by the Bureau of Land Management (Conservation Biology Institute).

Within these federal lands there are over 40 native villages with over 30,000 people.  Most of these people live a subsistence lifestyle, depending on the shrub/grassland to survive.  This area supports hunting and trapping for a variety of birds and mammals.  Many of these areas have rich salmon runs and other species of fish.  Native reindeer herders in Southwest Alaska depend on the grasses of this range type to feed their animals.

Shrub/grassland rangelands are the most common areas used for agriculture in Alaska.  About 121 km² (30,000 acres) of land, mostly in the Matanuska Valley, Tanana Valley, and Kenai Peninsula are used for agriculture in the state.  About 48,560 km² (12 million acres) on the Seward Peninsula are used for reindeer grazing (Parson 2001).

Some regions of this range type have also been used for mineral and oil extraction.  Because much of the land in Southwest Alaska is held in National Parks and Wildlife Refuges, exploration and development has been somewhat limited.  However, there are a few companies that mine zinc, lead, and silver in the southwest region of the state.  The Cominco Alaska Corporation mines about 2 million tons of these minerals from the Red Dog deposit north of Kotzebue. The Kenai Peninsula on the other hand supports a good-sized oil and natural gas industry in the Soldotna, Kenai, and Nikiski area.  Until development of the North Slope, this region produced the most oil in Alaska.  Most of the fuel from this region stays within Alaska and is used by the Alaska Nitrogen Products Fertilizer Plant, the Tesoro Refinery, Enstar, and other state electrical companies.  Oil and natural gas on the Kenai contributes to about $100 million dollars into the economy of South Central Alaska each year (Barrett 2000).

Future Concerns

Because much of the shrub/grassland range type is highly populated and often visited, one of the greatest risks to it is degradation due to population increases.  Between 1990 and 2000 Alaska’s population increased about 14%, slightly higher than the national average, and the next 10 years growth is expected to be similar (University of Alaska-Anchorage).  The South Central region is one of the fastest growing parts of the state.  Between 2000 and 2003 the fastest growing region of Alaska was the Matanuska – Susitna Valley with a 15.2% population increase, followed by Anchorage with a 4.9% increase, and the Kenai Peninsula with a 2.9% increase in population (United States Census Bureau).  More people means more pressure on the land and resources for places to live, transportation, recreation, jobs, and energy needs.

With large population growth in South Central Alaska, oil and natural gas companies, Unocal and Marathon have been expecting increases in job and energy needs for the region.  They have very actively been looking for new reserves on the Kenai Peninsula for the past few years. (Spence 2001)  One of the most recent discoveries was a very large deposit found 72 km (45 miles) south of Kenai (city) in 2002 (Associated Press).  Future goals include heavy exploration and extraction from the Cook Inlet basin and potentially a South Central Alaska Oil Pipeline system.  Over 50% of the Cook Inlet watershed is state owned and undesignated, which leaves it incredibly available to developing energy needs.  Increased mining development is a risk in Southwest Alaska and one of the main associated concerns is the increase in roads going into these remote locations and the allied damage (Conservation Biology Institute). 

Increase in human populations also adds stress to the natural areas and animal populations if they are not adequately regulated.  The natural resources of the United States are often described as being “loved to death” because they are used to the point where plant and animal populations are impacted and may find a difficult or impossible recovery. The shrub/grass rangelands are pretty hearty ecosystems, but like all ecosystems they have areas of weakness, such as riparian zones and wetlands.

Although there is risk for shrub/grassland depletion, a major question for Alaska may actually be the increase in shrub lands.  This past summer, fire ripped through over 6 million acres of Interior Alaska.  Shrub/grasslands are one of the heartiest ecosystems, able to survive practically anywhere.  They often occupy the late primary and secondary stages of succession.  Any land disturbance including logging, mining, glacial recession, or road building could all lead to the development of shrub/grasslands.  Fragmentation of forests also promotes shrub growth along the forest interfaces (Smith and Smith 2001).

The increasing average temperatures in Alaska are increasing the quantity of shrub/grasslands.  Over the past 50 years the average temperature in Alaska has risen about 2°C.  The impermeable permafrost layers that underlay much of the shrub/grasslands may melt as much as 9 m (30 ft.) over the 21st century (Parson 2001). In several places this means standing surface water will infiltrate leaving the upper soils much dryer than in the past (Smith and Smith 2001).  The warmer temperatures and smaller acreage of frozen soils may lead to increased agriculture in South Central and Southwest Alaska, or current operations may need more irrigation because of increased water infiltration.  Agricultural operations could face additional problems with warming temperatures, including insect infestation and invasive plant species.

Shrubs are known for their ability to survive in challenging areas with minimal moisture.  Current research in Alaska has actually compared photos from the 1940’s with 2004 and the respective vegetation growing in northern Alaska.  Results of this study show that shrubs have moved northward grew larger, patches expanded, and patches filled in.  In 90% of the photograph/research locations shrubs were more prevalent than in the 1940’s (Tape 2003?).  Research conducted in Colorado used large heaters to warm and dry a grassland surface.  Over time, they saw the increase in shrub species, accompanied by a decline in graminoids and forbs.  Scientific research is predicting the northward movement of shrub lands and boreal forests, meaning many ecological changes for Alaska (Smith and Smith 2001).

One more possibility associated with warming of the arctic regions is the increased amount of carbon dioxide (CO₂) being released from arctic soils. With increased temperatures and decrease in permafrost, more microbial decomposers can survive.  With the large accumulation of organic materials in shrub / grasslands, this could mean huge amounts of CO₂, one byproduct of decomposition, being released to the atmosphere.  Research conducted at the Harvard Forest in Massachusetts, elevated soil temperatures by 5°C and found a 60% increase in soil respiration and a 36% decrease in carbon from the organic horizon.  The research concluded that a huge amount of carbon is removed from the soil via microorganisms and released into the atmosphere as CO₂, thus increasing greenhouse gasses and building potential for continued anthropological impacts on global warming to occur (Smith and Smith 2001). 

By Chris Swisher and Kristin Fischer
(editorial revision by John Kawula)

References

Climate

Soils

Washburn, A. 1973. Periglacial Processes and Environments. New York: St. Martin's Press.

Vegetation

Hagenstein, R., T. Rickets. 2001. Beringia lowland tundra. [Online] Available from http://www.worldwildlife.org/wildworld/profiles/terrestrial/na/na1106_full.html  14 Oct. 2004.

Smith, R.L. and T.M. Smith. 2001. Ecology and field biology. 6th ed. San Francisco: Benjamin Cummings.

University Corporation for Atmospheric Research. n.d. Alaska Ecoregions. [Online] Available from http://www.ofps.ucar.edu/atlas/ivotuk_CD/reports/ecoregions.htm#_Soils 11 Oct. 2004.

Current Uses

Alaska Geographic. 1981. Alaska’s national interest lands.  Vol. 8, No. 4.  pp. 67, 111, 116, 154-155.

Barrett, J.  2000.  Unocal plans to stay active on peninsula.  Kenai Peninsula Clarion [Online] Available from  http://www.peninsulaclarion.com 15 Dec. 2004.

Conservation Biology Institute.  Beringia lowland/ upland tundra and Cook Inlet taiga. [Online] Available from http://www.consbio.org/cbi/pacnw_assess/er01-02/setting.htm 15 Dec. 2004.

Parson, E.A. 2001.  US Global Change Research Information Office.  Potential consequences of climate variability and change for Alaska.  [Online] Available from http://www.gcrio.org/NationalAssesment/10AK.pdf 15 Dec. 2004.

United States Fish and Wildlife Service. National Wildlife Refuges: Alaska.  [Online] Available from http://alaska.fws.gov/mission.htm 15 Dec. 2004.

Future Concerns

Associated Press, Anchorage.  2002.  Unocal strikes onshore gas discovery.  Kenai Peninsula Clarion Online. Available from  http://www.peninsulaclarion.com 15 Dec. 2004.

Smith, R.L. and T.M. Smith.  Ecology and field biology, 6th ed. 2001.  San Francisco: Benjamin Cummings, pp. 577-600, 700-703.

Spence, H.  2001.  Land leased in oil gas pursuit.  Kenai Peninsula Clarion Online. Available from http://www.peninsulaclarion.com 15 Dec. 2004.

Tape, K. 2003? A half-century of change in arctic alaskan shrubs: a photographic-based assessment.  [Online] Available from http://www.laii.uaf.edu/warming/warming.cfm 15 Dec. 2004.

United States Census Bureau.  Alaska population change: 2000-2003. [Online] Available from  http://www.epodunk.com/top10/countypop/copop2.html 15 Dec. 2004.

United States Geological Survey.  Biology: Southwest Alaska.  [Online] Available from http://biology.usgs.gov/stl/snt/noframe/ak177.htm 15 Dec. 2004. [URL no longer available April 18, 2005.]