Savannah
Scenario model
Current ecosystem state
Select a state
Management practices/drivers
Select a transition or restoration pathway
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Transition T1A
Heavy, continuous, season long grazing with no fire or woody species management.
More details -
Transition T1B
Tillage to facilitate production agriculture.
More details -
Transition T2A
Tillage to facilitate production agriculture.
More details -
No transition or restoration pathway between the selected states has been described
Target ecosystem state
Select a state
State 1
Reference State
Description
The Reference State (1) describes the range of vegetative community phases that occur on the Savannah ecological site where the natural processes are mostly intact. The Reference Community (1.1) is a representation of the native plant community phase that occupies a site that has been minimally altered by management. The Degraded Native (1.2), the At-Risk (1.3), and the Excessive Litter (1.4) Communities result from management decisions that are unfavorable for a healthy Reference Community (1.1). High perennial grass cover and production allows for increased soil moisture retention, vegetative production, and overall soil quality.
Submodel
Description
The Native/Invaded State (2) has been degraded from the Reference State (1) and much of the native, warm-season tall and mid grass community has been replaced by warm-season short grasses and cool-season grasses. The loss of warm-season, tall and mid grasses has negatively impacted energy flow and nutrient cycling. The woody component has expanded significantly and shading by the overstory has also increased. Water infiltration is reduced due to the shallow root system and rapid runoff characteristics of the invaded plant communities. Alterations to the soil and the hydrological processes make return to the Reference State (1) unlikely. The Native/Invaded State (2) includes the Invaded Woody Community (2.1) and the Eastern Red Cedar Community (2.2).
Submodel
Description
The threshold to the Sod-busted State (3) is crossed as a result of mechanical disturbance to facilitate production agriculture. If farming operations are suspended, the site can be abandoned or seeded. Abandonment results in the Natural Reclamation Community (3.3). Seedings are either a tame pasture forage mixture, the Seeded Pasture Community (3.2), or a mixture of native grasses and forbs, the Reseeded Native Grass Community (3.1).
Permanent alterations of the soil community and the hydrologic cycle make restoration to the Reference State (1) extremely difficult, if not impossible. Formation of a compacted plow pan in the soil profile is likely.
Submodel
Mechanism
Heavy, continuous, season long grazing, rotational grazing with inadequate growing season recovery periods (deferment), or haying with inadequate recovery periods will cause the Reference State (1) to lose a significant proportion of warm-season, tall and mid grass species and cross a threshold to the Native/Invaded State (2). Water infiltration and other hydrologic functions will be reduced due to the root matting presence of sod forming grasses. With the decline and loss of deeper penetrating root systems, soil structure and biological integrity are catastrophically degraded to the point that recovery is unlikely.
Additionally, increasing woody encroachment also occurs due to overgrazing and lack of fire and woody species management. The expansion of the overstory blocks more sunlight, creating a more competitive environment for a shade tolerant understory. Mechanical removal with follow up stump treatment of the root sprouting species and implementation of a prescribed burning regime will limit the encroachment of woody species.
Once this transition occurs, it is highly unlikely that grazing management and woody species management alone will return the community to the Reference State (1).
Mechanism
The threshold to the Sod-busted State (3) is crossed as a result of mechanical disturbance to facilitate production agriculture. If farming operations are suspended, the site can be abandoned, which will result in the Natural Reclamation Community (3.3), or be seeded to a tame pasture forage mixture, the Seeded Pasture Community (3.2) or to a mixture of native grasses and forbs, the Reseeded Native Grass Community (3.1).
Mechanism
The threshold to the Sod-busted State (3) is crossed as a result of mechanical disturbance to facilitate production agriculture. If farming operations are suspended, the site can be abandoned, which will result in the Natural Reclamation Community (3.3), or be seeded to a tame pasture forage mixture, the Seeded Pasture Community (3.2) or to a mixture of native grasses and forbs, the Reseeded Native Grass Community (3.1).
Model keys
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The Ecosystem Dynamics Interpretive Tool is an information system framework developed by the USDA-ARS Jornada Experimental Range, USDA Natural Resources Conservation Service, and New Mexico State University.