Loamy Terrace Savanna

Description

The reference plant community is categorized as a mesic bottomland oak savanna. The two community phases within the reference state are dependent on fire and seasonal flooding regimes. Decreased fire regimes allowed the canopy to close, and increased flood events resulted in an understory populated by species tolerant of wetter soil conditions. Similarly, increased fire regimes and decreased flood events opened the canopy and altered the understory composition, cover, diversity, and productivity.

Submodel

Description

Periodic fire maintained a moderate tree canopy and an understory more reminiscent of a wet prairie. However, the past 150 years of fire suppression efforts have transitioned the reference oak savanna community into a closed-canopy woodland state. Along with fire suppression, the channelization of streams and rivers and the development of reservoirs has also contributed to a closing of the canopy as well as causing a significant shift in species composition. (Nelson 2010; NatureServe 2015).

Submodel

Description

The cool-season pasture state occurs when the reference state has been anthropogenically-altered for livestock production. Early settlers harvested the trees for timber and fuel and seeded such non-native cool-season species as Kentucky bluegrass (Poa pratensis L.), converting the woodland to pasture (Smith 1998; IDNR 2013). Over time, as lands were continually grazed by large herds of cattle, the non-native species were able to spread and expand across the site, reducing the native species diversity. However, these sites are difficult to maintain due to frequent flooding and low available water capacity.

Submodel

Description

The Midwest is well-known for its highly-productive agricultural soils, and as a result, much of the MLRA has been converted to cropland, including portions of this ecological site. 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 (Zea mays L.) and soybeans (Glycine max (L.) Merr.) are the dominant crops for the site. These areas are likely to remain in crop production for the foreseeable future.

Submodel

Description

The combination of natural and anthropogenic disturbances occurring today has resulted in a number of ecosystem health issues, and restoration back to the historic reference condition is likely not possible. Many natural lowland communities are being stressed by non-native diseases and pests, habitat fragmentation, permanent changes in hydrologic regimes, fire suppression, and overabundant deer populations on top of naturally-occurring disturbances (severe weather and native pests) (Flickinger 2010; Nelson 2010). However, these habitats provide multiple ecosystem services including carbon sequestration; clean air and water; soil conservation; biodiversity support; as well as a variety of cultural activities (e.g., hiking, hunting) (Millennium Ecosystem Assessment 2005; Flickinger 2010). Therefore, conservation of lowland savannas should still be pursued. Habitat reconstructions are an important tool for repairing natural ecological functioning and providing habitat protection for numerous species of Loamy Terrace Savannas. Therefore ecological restoration should aim to aid the recovery of degraded, damaged, or destroyed ecosystems. A successful restoration will have the ability to structurally and functionally sustain itself, demonstrate resilience to the ranges of stress and disturbance, and create and maintain positive biotic and abiotic interactions (SER 2002). The reconstructed savanna state is the result of a long-term commitment involving a multi-step, adaptive management process.

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