Ponded Organic Floodplain Shrub Swamp

Description

The reference plant community is categorized as a shrub swamp community, dominated by hydrophytic woody and herbaceous vegetation. The two community phases within the reference state are dependent on ponding. The depth and duration of ponded water alters species composition, cover, and extent. Drought and infrequent fire have more localized impacts in the reference phases, but do contribute to overall species composition, diversity, cover, and productivity.

Submodel

Description

Hydrology is the most important determinant of wetlands and wetland processes. Hydrology modifies and determines the physiochemical environment (i.e., sediments, soil chemistry, water chemistry) which in turn directly affects the vegetation, animals, and microbes (Mitsch and Gosselink 2007). Human activities on landscape hydrology have greatly altered Ponded Organic Floodplain Shrub Swamps. Alterations such as agricultural tile draining and conversion to cropland on adjacent lands in addition to stream channelization and damming have changed the natural hydroperiod and rate of sedimentation as well as increased nutrient pollution (Mitsch and Gosselink 2007). Long-term fire suppression has also allowed unnatural succession and dominance by floodplain trees.

Submodel

Description

The forage state arises when the site is converted to a farming system that emphasizes domestic livestock production, known as grassland agriculture. Tree removal, fire suppression, periodic cultural treatments (e.g., clipping, drainage, soil amendment applications, planting new species and/or cultivars, mechanical harvesting) and grazing by domesticated livestock transition and maintain this state (USDA-NRCS 2003). Early settlers seeded non-native species, such as smooth brome (Bromus inermis Leyss.) and Kentucky bluegrass (Poa pratensis L.), to help extend the grazing season (Smith 1998). Over time, as lands were continuously harvested or grazed by herds of cattle, these species were able to spread and expand across the landscape, reducing the native species diversity and ecological function.

Submodel

Description

The cropland state is the dominant land condition throughout the MLRA today. Agricultural tile drains used to lower the water table and the continuous use of tillage, row-crop planting, and chemicals (i.e., herbicides, fertilizers, etc.) have effectively eliminated the reference community and many of its natural ecological functions in favor of crop production. Corn and soybeans are the dominant crops for the site, and oats (Avena L.) and alfalfa (Medicago sativa L.) may be rotated periodically. These areas are likely to remain in crop production for the foreseeable future.

Submodel

Description

Shrub swamp habitats provide multiple ecosystem services including flood abatement, water quality improvement, and biodiversity support (Mitsch and Gosselink 2007). However, many swamp communities have been eliminated as a result of type conversions to agricultural production, changes to the natural hydrologic regime, and invasion of non-native species, thereby significantly reducing these services (Annen et al. 2008). The extensive alterations of lands adjacent to Ponded Organic Floodplain Shrub Swamps or the depletion of the historic organic soils may not allow for restoration back to the historic reference condition. But ecological reconstruction can aim to aid the recovery of degraded, damaged, or destroyed functions. A successful reconstruction will have the ability to structurally and functionally sustain itself, demonstrate resilience to the natural ranges of stress and disturbance, and create and maintain positive biotic and abiotic interactions (SER 2002; Mitsch and Jørgensen 2004).

Submodel