Closed Depression
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 grazing or haying with inadequate recovery periods.
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
Description
The Reference State (1) describes the range of vegetative communities that occur on the Closed Depression ecological site where the range of natural variability under historic conditions and disturbance regimes is mostly intact. High perennial grass cover and production allows for increased vegetative production and overall soil quality.
The Reference State includes four plant community phases which are the Reference or Western Wheatgrass (Pascopyrum smithii) Community (1.1), the Grass-like/Forb or Sedge-Rush/Smartweed (Carex-Juncus/Polygonum) Community (1.2), the At-Risk or Western Wheatgrass-Saltgrass (Pascopyrum smithii-Distichlis spicata) Community (1.3), and the Excessive Litter or Western Wheatgrass/Common Spikerush (Pascopyrum smithii/Eleocharis palustris) Community (1.4). The Reference Community is a representation of the native plant community phase that occupies a site that has been minimally altered by management and which occurs during a drier weather cycle while the Grass-like/Forb Community also represents the native plant community phase that has been minimally altered by management but which occurs during a wetter weather cycle. Degraded Native Grass and Excessive Litter Communities result from management decisions that are unfavorable for a healthy Reference Community.
Submodel
Description
The Native/Invaded Grass State (2) has transitioned from the Reference State (1) and much of the native cool-season midgrass and grass-like components have been replaced by warm-season shortgrass and introduced cool-season grasses, resulting in negative impacts on energy flow and nutrient cycling. Water infiltration is reduced due to the shallow root system and rapid runoff characteristics of the shortgrass sod community. The Native/Invaded Grass State (2) includes the Shortgrass Sod/Invasive Grass Community (2.1).
Submodel
Description
The threshold to the Sodbusted State (3) is crossed as a result of mechanical tillage to facilitate production agriculture. When the land is no longer cropped, the resulting state is the Sodbusted State. When farming operations are suspended, the site can seeded to native grasses and forms resulting in the Reseeded Native Grass Community (3.1), be seeded to a tame pasture forage mixture resulting in the Seeded Pasture Community (3.2) or be abandoned with no seeding which will result in the Natural Reclamation Community (3.3). 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 plowpan in the soil profile is likely.
Submodel
Mechanism
Heavy continuous season-long grazing or haying without adequate recovery periods will cause the Reference State (1) to lose a significant proportion of cool-season, tall- and midgrass species and cross a threshold to the Native/Invaded State. 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. Once this occurs, it is highly unlikely that grazing management alone will return the community to the Reference State.
Mechanism
The Reference State (1) is significantly altered by tillage to facilitate production agriculture. The disruption to the plant community, the soil and the hydrologic cycle make restoration to a true Reference State unlikely.
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.