Wetlands are a unique and dynamic ecosystem within the landscape which provide habitat for various fish and wildlife populations, as well as a multitude of plant species. Wetland locations are identified by the presence of plants adapted for saturated conditions (i.e. hydric vegetation), visible presence or evidence hydrology during the plant growing season, and a unique physiochemical environment (i.e. hydric soils). All three of these aspects are directly related and must be present simultaneously for an area to be classified as a wetland. In addition to hydrology, vegetation, and soil, the climate and geomorphology of an area can also have a large role on wetland ecosystems. The following provides a brief overview of the interlinked relationships between these essential components within a wetland ecosystem.
Generally speaking, an area’s climate and geomorphology can have a direct effect on the overall hydrology, physiochemical qualities, and abundance of biota within a wetland ecosystem. The climate in an area will have an effect not only on monthly and annual precipitation, but also the level of water which is received into or evaporated out of a wetland area. Basin geomorphology has an effect on how long a wetland will store or process water (i.e. a shallow marsh holding water for extended periods of time versus an emergent wetland within a floodplain), where the wetland forms within the landscape, and quality of available habitat for various plant and animal species.
The frequency and duration of time where hydrology is available within a wetland can have a direct effect on the physiochemical environment. For example, the length of time water stays within a wetland will influence the level of oxidation or reduction that occurs within the soils and related water chemistry. Hydrology is also responsible for the inflow and export of nutrients, sediments, biotic and abiotic material, pollution, and debris in and out of a wetland area, all of which alter the physiochemical environment. Additionally, hydrology can also influence the biotic communities in a wetland environment. Since wetlands are located between two terrestrial ecosystems, they form a boundary between an aquatic area and an upland area. The level and duration of water within a wetland will directly affect available habitat for various wildlife species and living conditions for vegetative species. Slight changes hydrology can have an impact on biotic communities, positive or negative, dependent on the change in water level, flow, duration, etc. For example, a flooded waterway will temporarily increase fish habitat while decreasing mouse habitat.
The physiochemical environment within a wetland can have a direct effect on both hydrology and biota. Wetland hydrology can be affected by the physiochemical environment through the buildup of sediments, which can result in a change of the basin geometry or alter the hydrologic inflows or outflows. The change in hydrology as a result from sediment build up can reduce the level of available oxygen for plant species, and can therefore have a direct impact on wetland biota. Depending on the level of duration, these alterations in water levels or amount of sediments/nutrients in the soil could also result in significant changes to the composition of vegetative species and habitat for animals which are adapted to shallow or deep water environments.
As mentioned above, the success and diversity of wetland biotic communities is directly linked to the hydrologic and physiochemical conditions. However, biotic communities can also influence changes to both the hydrology and physiochemical environment through cybernetic control, or direct biotic feedback. A common example of biotic feedback and its influence on wetland hydrology is demonstrated by the actions of beavers, which are well known for their ability to create and destroy wetland areas. Once beavers establish a dam across a normally flowing steam, water becomes backed up and results in the creation of a new wetland area. Additionally, the reduction in water flows downstream can alter the amount of available nutrients in the soil and affect the success of established vegetative species associated with the stream and within the floodplain, changing the physiochemical environment.
As mentioned above, wetlands are dynamic ecosystems. All three essential wetland components, hydrology, physiochemical environment, and biota are directly dependent upon each other and respond in relation to an area’s climate and geomorphology through complex, interlinked relationships.