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Home > Climate > Mire/Bog/Fen
Mire/Bog/Fen
Maps
and Photos
of mire/bog/fen range type
Mire/Bog/Fen Climatic Overview
The mire, bog and fen range type,
in Alaska, is characterized by short, warm summers and long, cold
winters with heavy annual precipitation. It occurs throughout the
state, particularly in low-lying areas where glaciers retreated and
along the margins of fresh waterways. The high annual
precipitation, snow cover, and underlying permafrost keep the soils in
this area waterlogged year round. The soil is acidic, poor in
nutrients and rich in organic matter due to the anaerobic conditions
which decrease decomposition. Mires, which are usually
classified into bogs or fens, are ancient freshwater wetlands with a
heavy accumulation of peat due to thousands of years of wetland
succession. They contain sedges and sphagnum mosses which form
the thick layers of peat upon their death. They are called bogs
when
dominated by sphagnum mosses and fed by nutrients contained in
precipitation, surface water, and groundwater. They are called
fens when dominated
by sedges and fed by nutrients in precipitation only (Aerts et al
1999). Trees are few and stunted; the remaining vegetation is
diverse and very specialized to withstand the anaerobic and acidic
conditions.
Mire/Bog/Fen Soils
The soils in this range type are waterlogged and rich
in organic matter. The organic horizon of the soil is saturated
with water creating anaerobic conditions. These peatlands form as
a result of high precipitation, poor drainage, low evaporation, and low
transpiration. The cold subsurface, permafrost, impedes water
drainage promoting peat development. However, permafrost is not
present in all areas of this range type. According to the State Soil
Geographic Database of the Natural Resource Conservation Service, this
range type is characterized by various soil types with none covering
more than 10% of the overall area. The most prevalent type is pergelic
cryaquepts – pergelic cryochrepts - histic pergelic
cryaquepts. Histic soils are soils having greater than 15cm
(5.9
in.) but less than 40cm (15.7 in.) of organic horizon and pergelic
soils are soils having a mean annual soil temperature of less than
0°C (Ping 1999). Aquepts are the wet Inceptosols which
include a wide variety of soils with a cambic horizon, a horizon that
has been physically altered or chemically transformed, and an ochric
epipidon (Soil Survey Staff 1999). These are soils with poor to
very poor drainage. Cryaquepts are the cold Aquepts found on
flood plains and low lying areas. Ground water is typically at a
high level close to the soil surface and the soil is covered with
standing water for some time each year. Cryofibrists are also
found in this range type; they are the cold, wet Histosols in which
organic matter only slightly decomposes (Swanson 2002).
Characteristics of other common soil types in these areas include
minimally developed horizons, aquic conditions, high levels of
decomposing material, and the presence of an umbric epipedon, which is
a thick, dark, acidic horizon common in wet soils (NRCS 2004). Cold
temperatures limit the use of all of these soils but they do support
natural vegetation.
Vegetative Community of the Mire/Bog/Fen Range Type
A variety of specialized plants grow in mires, bogs
and fens. Due to the anaerobic conditions and low nutrient
availability some carnivorous plants grow there. These include
sundew (Drosera rotundifolia) which captures insects with its
sticky
leaves and pitcher plant (Sarracenia purpurea) which drowns
insects in
it hollow, liquid-filled leaves. Sphagnum moss is an important
plant to bogs and one of the first species to colonize these
wetlands. The top of the plant grows continuously while the lower
portions die off increasing the peat accumulation and allowing other
plants to gain a solid footing. Sphagnum absorbs large quantities
of water preventing evaporation and there is some evidence that it
increases the acidity of the bog which also limits decomposition (Young
1994). Sedges such as cottongrasses (Eriophorum spp.) grow
in
fens and form large, dense mats. Heath plants are also typical in
this range type. These include: Labrador tea (Ledum
groenlandicum), arctic bell heather (Cassiope tetragona),
Lapland
rosebay (Rhododendron lapponicum), alpine bearberry (Arctostaphylos
alpina), tundra bilberry (Vaccinium uliginosum), and alpine
azalea
(Loisleuria procumbens).
Many of these plants exhibit xeromorphic
characteristics which is
typical of plants adapted to dry conditions; this may be due to the
acidic condition of the water present. These xeromorphic
characteristics include a thick, waxy cuticle and undercurled leaf
margins to help prevent water loss. Pure stands of swamp
horsetail may exist in some bogs. Other plants that may be
present include: wild iris (Iris setosa), bog rosemary (Andromeda
polifolia), bog blueberry (Vaccinium uliginosum), shrubby
cinquefoil
(Potentilla fruiticosa), bog saxifrage (Saxifraga hirculus),
and
buckbean (Menyanthes trifoliate) (O’Clair et al. 1997, and Pratt
1989).
Current Uses of Mire/Bog/Fen Range
In Alaska, the mire/bog/fen rangeland type is
considered to be a part of the state’s wetlands. Overall, 55% of the
land area of Alaska is classified as wetlands, although not all of
these wetlands are suitable for range use. In contrast, only 5% of the
land area of the lower 48 United States is classified as wetlands
(Perkins, 2000). One of the most valuable uses of Alaska’s wetlands,
including the mire/bog/fen rangeland, is peat harvesting. In 2003, the
output of peat from Alaska was 22,937 cubic meters (30,000 cubic yd.)
with a value of approximately $190,000. Peat is the decaying remains of
all types of plant material and is present in large quantities in bogs
and fens. Sphagnum moss, one of the main types of vegetation in the
bogs and fens of Alaska, is also including in harvesting for peat moss
(Jasinski 2003).
The principle use of peat moss in the United States is
to increase the water capacity and enhance the texture of agricultural
soils. It serves the same function that it does in its natural setting,
where it retains water in the bogs and fens that comprise part of
Alaska’s rangeland. Peat moss is also useful as a filter for
pollutants, another role it plays in its natural environment. In an
industrial area, it can filter toxic materials found in sewage and
storm-drain water. Peat moss, including sphagnum moss, is highly
absorbent in oil and fuel spills on land and water when in its
dehydrated form. Additional uses of peat are the extraction of gas
products for fuel, paper manufacturing, fermentation for alcohol and
assorted medical uses (Eslick 2001). Despite its usefulness, the short
growing and harvest season in Alaska makes it difficult to harvest as
much peat as might otherwise be possible.
Future Concerns
In the future, climate change is one of the foremost
concerns for Alaska wetlands. Research has shown a warming trend
in Alaska of approximately 0.75 degrees Celsius per decade over the
last three decades. If this current climate trend continues, Alaska
could experience a major landscape shift from forests to bogs, and a
change in the composition of grasslands and wetland ecosystems due to
permafrost thawing (Alaska 1998). While it is hard to predict the
effects of climate change in Alaska, research shows that warmer, drier
summers and milder, wetter winters are likely. If this happens, there
will be a greater potential for summer drought to cause peat loss and
bog contraction.
In mires, bogs, and fens, increased temperature will
result in higher productivity of organic matter for a time, but it will
also result in faster decomposition. In short, peat will form faster,
but it will also decompose faster. Because decomposition releases
carbon gases into the atmosphere, the higher rate of decomposition with
a warmer climate may cause the bogs to become more of a carbon source
than the carbon sink that they currently are (Moore 2001). A
carbon source releases carbon gases into the air, while a carbon sink
absorbs large amounts of carbon from the air (Eslick 2001). Some
researchers believe that carbon sinks help to offset some of the
effects of global warming due to the overwhelming amount of carbon
sources already present. Bogs and wetlands are examples of carbon
sinks, as is the tropical rainforest. Losing them may negatively
affect the composition and quality of our atmosphere.
Another concern for the bogs and fens of Alaska is the
increasing rate of urbanization and industry. Already in Alaska, mires
and bogs have been destroyed and filled in to expand infrastructure for
oil, oil exploration, and to accommodate the growing population
(Joosten 2003). In the past, there has been conflict in Alaska
between people who would like to see state wetlands preserved and those
who would like to see more development (Perkins 2000). Although
development of mires and bogs is managed quite closely by state and
federal regulations, it is highly likely that more of this unique
environment will be lost to urban growth and an increasing state
population in the future.
By Kim Lane and Aimee Chlebnik
(editorial revision by John Kawula)
References
Climate
Aerts, R., J. Verhoeven, D. Whigham. 1999.
Plant-Mediated Controls On Nutrient Cycling In Temperate Fens And Bogs.
Ecology 80(7):2170-2181.
Soils
Natural Resource Conservation Service. 2004. NRCS
Soils. [On-line] Available http://soils.usda.gov.
17 Oct.
Ping, C., 1999. End Summer Project Activity Report.
[Online] Available http://www.joss.ucar.edu/atlas/ping_991.html.
15 Oct. 2004.
Soil Survey Staff, 1999. Soil taxonomy: a basic
system of soil classification for making and interpreting soil
surveys. Second Edition. United States Department of Agriculture,
Natural Resource Conservation Service Agriculture Handbook Number 436.
Swanson, D., 2002. Soil Survey of Gerstle River
Area, Alaska. United States Department of Agriculture, Natural
Resource Conservation Service.
Vegetation
O’Clair, R., R. Armstrong, R. Carstensen.
1997. The Nature of Southeast Alaska, a guide to plants animals,
and habitats. 2nd ed. Alaska Northwest Books, Anchorage, AK.
Pratt, V. 1989. Field guide to Alaskan
wildflowers. Alaskakrafts Publishing, Anchorage, AK.
Young, S. 1994. To the Arctic, an
introduction to the far northern world. John Wiley & Sons,
Inc., New York, NY.
Current Uses
Eslick, J. 2001. Bogs: a web presentation. [On-line]
Available http://www.emporia.edu/earthsci/student/eslick2/bog_report.html.
22 April 2005.
Jasinski, S. 2003. Peat. [On-line] Available http://minerals.usgs.gov/minerals/pubs/commodity/peat/peat_myb03.pdf
22 April 2005.
Perkins, H. 2000. Army Corps of Engineers regulatory
program plays a major role in the use of Alaska’s wetlands. [On-line]
Available http://www.hq.usace.army.mil/cepa/releases/Alaska.htm.
22 April 2005.
Future Concerns
Alaska Regional Assessment Continues. 1998. [On-line]
Available http://www.usgcrp.gov/usgcrp/Library/nationalassessment/newsletter/1998.07/Alaska.html.
22 April 2005.
Joosten, H. 2003. Perspectives of global peatland use
and conservation. [On-line] Available http://www.imcg.net/imcgnl/Newsletter%202003-4%20html/kapitel9.htm.
22 April 2005.
Moore, P.D. 2001. The future of cool temperate bogs.
Environmental Conservation 29(1): 3-20.
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