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Ecology & Ecosystems

Ecology and Ecosystem

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.

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.

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.


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.


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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Last Page Update - Tuesday December 27, 2005