Ecology
and Ecosystem
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What is Ecology?
Ecology is the scientific
study of how living things interact with each other and their
environment. Ecological interactions take place and can be studied
scientifically in all environments, including cities and suburbs.
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Ecological
Concepts
Interdependence of living and nonliving
elements: Interdependence means that each element is somewhat, if not
totally dependent on the other for its ability to function.
Ecosystems: Ecosystems are groups
of living and nonliving things that function together in a particular
environment. For example, prairie dogs, birds, insects, low-lying grasses,
and shrubs (living elements) interact with each other as well as with
dry soil, high winds, and occasional downpours (nonliving elements)
to make up the shortgrass prairie ecosystem.
Community: All the organisms that
live together in an ecosystem comprise a community. In the above example,
prairie dogs, birds, insects, grasses, and shrubs make up the shortgrass
prairie community.
Habitat: Good habitat has four essential
components: food, water, shelter, and space. Each species has different
requirements for the types and amounts of each habitat component. Five
common urban habitats include: the urban edge, the inner city, the backyard,
the riparian corridor, and the park and open space. In the Front Range,
there are countless habitat types and more than 350 common species of
wildlife that exist in this area.
Source: Moorhead, Carol
Ann. Colorado Backyard Wildlife. Roberts Rhinehart Publishers 1992.
pages 25-32.
What is
an Ecosystem?
Ecosystems encompass all the parts
of a certain environment, including the living (biotic) plants and animals,
and the nonliving (abiotic) components, such as soil, water, air, and
the sun’s energy. Ecosystems transition into another one with little
change or distinction; for example, it is hard to tell exactly where
a stream turns into a river.
Every ecosystem contains species
of plants and animals. Each species occupies its own ecological niche
or role that it fulfills in the environment. Ecosystems found in the
Boulder Creek Watershed include plains grasslands, mountain grassland
and meadows, lowland riparian, mountain riparian, ponderosa pine forest,
aspen groves, lodgepole pine forests, alpine tundra and the aquatic
ecosystem. The focus of this section will be the lowland and mountain
riparian zones and the aquatic ecosystem.
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Lowland
Riparian Ecosystems
Lowland riparian ecosystems
are found along banks of rivers, streams and other bodies of water
and include floodplain woodlands and marshes. They are narrow,
transitional zones between aquatic and terrestrial ecosystems
with distinct vegetation and soils. Before the development of
the city of Boulder, the only deciduous trees in the Boulder Creek
Watershed where found in the riparian ecosystem.
Trees and other vegetation
help to moderate intense winds and sunlight in this ecosystem.
Often soils are young and moist, with a high water table and poor
drainage due to continuous changes in water flow (drought or flood)
or erosion.
Lowland river bottoms and
marshes are the most productive natural ecosystems in the regionÑfor
plants and wildlife. Many animals live in or near the riparian
zone because of the lush forage, water, and abundant denning or
nesting sites. Riparian zones also offer a refuge to animals that
live in other ecosystems. Many bird, reptiles, amphibians and
small mammals make their homes in the riparian ecosystem.
Humans have used and affected
the lowland riparian and wetland ecosystems. Impacts to these
ecosystems include mining gravel along stream banks, cutting cottonwoods
for firewood and lumber, building housing developments in the
flood plain, grazing cattle, and artificially channelizing and
damming waterways for flood protection and water supplies.
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Mountain
Riparian Ecosystems
Mountain riparian ecosystems
are found adjacent to streams, ponds and lakes. Small meadows
dominated by deciduous trees and moisture-loving shrubs form this
ecosystem. High mountain streambanks and wetlands support a diverse
array of plant communities that provide food and cover for many
animal species.
Mountain riparian ecosystems
are found throughout forested mountains (5600 to 11,000 feet).
Since streams run through the mountains at all altitudes, riparian
ecosystems form continuous strands that cross the subalpine and
montane forests. At their upper edges the ecosystems pass through
tundra marshes; they merge with lowland riparian ecosystems at
their lower limits.
Riparian ecosystems in mountain
and subalpine regions have fewer species than at lower elevations,
but diversity is still high compared to most adjacent ecosystems.
They provide abundant food and cover for a variety of birds and
animals.
Mountain riparian ecosystems
have been greatly altered by human use. Some of the impacts in
this ecosystem include removal of beavers to create hay meadows
and cattle grazing, building transportation routes adjacent to
streams, mining peat bogs, housing developments, and mining of
minerals found in the mountains. Many aquatic reaches have been
stained yellow or orange with mineral deposits and are devoid
of insects and fish. This activity has directly impacted the mountain
riparian ecosystem and also impacted ecosystems downstream.
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Aquatic
Ecosystem
 Aquatic
ecosystems are streams, rivers, ponds, lakes and reservoirs. In these
ecosystems, the distribution of organisms is determined by water temperature,
clarity, current, the amount and kind of dissolved materials, and the
types of materials that line the stream or lake bottom.
Characteristics of streams, and
thus plant and animal habitats, change with elevation as the streams
flow from the mountains to lower elevations. At the highest reaches,
the water is cold and almost as pure as distilled water; stream beds
are steep and strewn with boulders; and dissolved oxygen levels are
high because of the cascading water and cold temperatures. Few aquatic
plants can survive the cold, swift moving, nutrient-poor waters of the
highest streams. In these places the major energy source is organic
detritus (leaves, twigs) which serve as food for microbes, aquatic insects
and other small organisms.
At middle elevations, stream channels
are not as steep and the stream bed has both boulders and rocks. Mid-elevation
streams alternate between deep, quiet pools and riffles: shallower areas
with a steeper slope, faster current, and a bed of large, cobble-sized
rocks. Pools and riffles each provide a unique habitat to stream inhabitants.
At middle elevations, where currents lessen and more phosphorous, nitrogen
and other plant nutrient are available in the water, a coating of periphyton
covers the stream bed rocks. This living film is an important food source
for insects and other invertebrates. It consists of algas, diatoms,
and water moss. Riffles are particularly productive areas, where periphyton-covered
rocks support a diverse insect community. Pools accumulate detritus
and are important sites for organic decomposition and nutrient recycling.
Riffles are important feeding grounds for trout, while pools provide
quieter water for them to rest.
At lower elevations, where streams
leave the mountains, the gradient declines and currents slow down causing
concentrations of dissolved salts to increase, temperatures to increase,
and oxygen content to decrease. Accumulations of suspended particulates
reduce the water’s clarity. At times, streams are extremely turbid,
especially during spring runoff. The sediments of low elevation stream
beds are more fine-grained than in the mountains, and consist of gravel,
sand or silt.
Healthy riparian ecosystems are
of prime importance to associated aquatic habitats. Riparian vegetation
helps hold stream bank soils in place, which in turn reduces the sediment
loads entering them. Riparian lands also contribute organic detritus
to streams, which often serves as the most important source of energy
for aquatic food webs.
Streams and rivers are inhabited
by a variety of aquatic organisms. The largest organisms are vertebrate
animalsÑfish and a few amphibians and reptiles. The invertebratesÑinsects,
snails, flatworms, leeches, and other small animals without backbonesÑare
far more numerous. There are two types of invertebrates: macroinvertebrates
are those that can be seen without a microscope; microinvertebrates
are those you can see only under a microscope.
Stoneflies, mayflies, caddisflies,
true flies, and riffle beetles collectively comprise about ninety percent
of the total macroinvertebrate fauna of the Boulder Creek Watershed
stream system. The most abundant fish found in the higher, cooler streams
of this area include brook, rainbow and brown trout. These species were
introduced into area streams more than 100 years ago. These exotic fish
species have reduced the population of the native cutthroat trout and
restricted its populations to the highest and steepest streams. In the
warm water streams of Boulder County, channel catfish, suckers and sunfish
are abundant.
Aquatic ecosystems are impacted
by a broad range of human activities. The ecosystem has been affected
by the following actions: heavy metal pollution from acid mine drainage;
dust and oil from roads; pesticides, fertilizers, animal waste from
agriculture; industrial wastes; heated water from power plant condensers;
and treated and untreated discharges from municipal sewage treatment
plants; damming rivers or building transbasin water diversions for drinking
water supply and irrigation; and introducing nonnative fish species
for sport fishing.
Human modifications have reduced
the number of destructive floods, increased the number of fish species,
and provided water to relatively dry places. However, in return we have
decreased the number of free-flowing streams and health aquatic ecosystems
to the point that they have become as endangered as the rare species
within them.
Source: Mutel, Cornelia
Fleischer and John C. Emerick. From Grassland to Glacier: the Natural
History of Colorado and the Surrounding Region. Johnson Publishing 1992.
pages 59-70; 71-85; 205- 226.
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