Clayey Bottomland
Scenario model
Current ecosystem state
Select a state
Management practices/drivers
Select a transition or restoration pathway
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Transition T1A
No fire, no brush management, improper grazing management, drought
More details -
Transition T1B
Brush management, crop cultivation, pasture planting, nutrient management, pest management
More details -
Restoration pathway R2A
Fire, brush management, proper grazing, range planting
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Transition T2A
Brush management, crop cultivation, pasture planting, nutrient management, pest management
More details -
Restoration pathway R3A
Fire, brush management, proper grazing, range planting
More details -
Transition T3A
No fire, no brush management, heavy continuous grazing, no pest management
More details -
No transition or restoration pathway between the selected states has been described
Target ecosystem state
Select a state
Description
Two communities exist in the Savannah State: the 1.1 Tallgrass Savannah Community and the 1.2 Midgrass Savannah Community. Community 1.1 is characterized by tallgrasses dominating the understory with woody species creating less than 20 perecent of the canopy cover. Community 1.2 is characterized by midgrasses dominating the understory and woody species making up 20 to 50 perecent of the overstory canopy cover.
Submodel
Description
Only one community is in the Woodland State, the 2.1 Dense Woodland Community. Community 2.1 is characterized by cool-season grasses and shade-tolerate dominating in the understory. Woody species occupy greater than 50 percent of the overstory.
Submodel
Description
Two communities exist in the Converted State: 3.1 Converted Land Community and the 3.2 Abandoned Land Community. The 3.1 Community is characterized by agricultural production. The site may be planted to improved pasture for hay or grazing. The site may otherwise be planted to row crops. The 3.2 community represents an agricultural state that has not been managed. The land is colonized by first successional species.
Submodel
Mechanism
Shrubs and trees make up a portion of the plant community in the Savannah State, hence woody propagules are present. Therefore, the Savannah State is always at risk for shrub dominance and the transition to the Woodland State in the absence of fire. The driver for Transition T1A is lack of fire and/or brush control. The mean fire return interval in the Savannah State is two to five years. Most fires will burn only the understory. Even with proper grazing and favorable climate conditions, lack of fire for 8 to 15 years will allow trees and shrubs to increase in canopy to reach the 50 percent threshold level. The introduction of aggressive woody invader species increases the risk and accelerates the rate at which this transition state is likely to occur. This transition can occur from any community within the Savannah State, it is not dependent on degradation of the herbaceous community, but on the lack of some form of brush control. Improper grazing, prolonged drought, and a warming climate will provide a competitive advantage to shrubs which will accelerate this process. Tallgrasses will decrease to less than five percent species composition.
Mechanism
The transition to the Converted State from either the Savannah State is plowed for planting to cropland or hayland. The size and density of brush will require heavy equipment and energy-intensive practices (i.e. rootplowing, raking, rollerchopping, or heavy disking) to prepare a seedbed. The threshold for this transition is the plowing of the prairie soil and removal of the prairie plant community. The Converted State includes cropland, tame pasture, and go-back land. The site is considered “go-back land” during the period between cessation of active cropping, fertilization, and weed control and the return to the “native” states. Agronomic practices are used to convert rangeland to the Converted State and to make changes between the communities in the Converted State. The driver for these transitions is management’s decision to farm the site.
Mechanism
Restoration of the Woodland State to the Savannah State requires substantial energy input. Mechanical or herbicidal brush control treatments can be used to remove woody species. A long-term prescribed fire program is unlikely to sufficiently reduce brush density to a level below the threshold of the Savannah State if not accompanied by some form of mechanical or chemical brush control. Brush control in combination with prescribed fire, proper grazing, and favorable growing conditions may be the most economical means of creating and maintaining the desired plant community. If remnant populations of tallgrasses, midgrasses, and desirable forbs are not present at sufficient levels, range planting will be necessary to restore the reference plant community. The driver for Restoration Pathway R2A is fire and/or brush control combined with natural restoration of the herbaceous community or active management of the herbaceous restoration process (range seeding). Restoration may require aggressive treatment of invader species.
Mechanism
The transition to the Converted State from the Woodland State (T2A) occurs when the Savannah is plowed for planting to cropland or hayland. The size and density of brush in the Woodland State will require heavy equipment and energy-intensive practices (i.e. rootplowing, raking, rollerchopping, or heavy disking) to prepare a seedbed. The threshold for this transition is the plowing of the prairie soil and removal of the prairie plant community. The Converted State includes cropland, tame pasture, and go-back land. The site is considered “go-back land” during the period between cessation of active cropping, fertilization, and weed control and the return to the “native” states. Agronomic practices are used to convert rangeland to the Converted State and to make changes between the communities in the Converted State. The driver for these transitions is management’s decision to farm the site.
Mechanism
Restoration from the Converted State can occur in the short-term through active restoration or over the long-term due to cessation of agronomic practices. Cropland and tame pasture require repeated and continual inputs of fertilizer and weed control to maintain the Converted State. If the soil chemistry and structure have not been overly disturbed (which is most likely to occur with tame pasture) the site can be restored to the Savannah State. Heavily disturbed soils are more likely to return to the Woodland State. Without continued disturbance from agriculture the site can eventually return to either the Savannah or Woodland state. The level of disturbance while in the converted state determines whether the site restoration pathway is likely to be R3A (a return to the Savannah State) or R3B (a return to the Woodland State).
Return to native communities in the Savannah State is more likely to be successful if soil chemistry and structure are not heavily disturbed. Preservation of favorable soil microbes increases the likelihood of a return to reference (or near reference) conditions. Converted sites can be returned to the Savannah State through active restoration, including seedbed preparation and seeding of native grass and forb species. Protocols and plant materials for restoring prairie communities is a developing part of restoration science. The driver for both of these restoration pathways is the cessation of agricultural disturbances.
Mechanism
Transition to the Woodland State (2) occurs with the cessation of agronomic practices. The site will move from the Abandoned Land Community when woody species begin to invade. After shrubs and trees have established over 50 percent, and reached a height greater than three feet, the threshold has been crossed. The driver for the change is lack of agronomic inputs, improper grazing, no brush management, and no fire.
Model keys
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