Sandy
Scenario model
Current ecosystem state
Select a state
Management practices/drivers
Select a transition or restoration pathway
- Transition T1 More details
- Restoration pathway R1 More details
- Transition T2 More details
-
No transition or restoration pathway between the selected states has been described
Target ecosystem state
Select a state
Description
State 1 Narrative:
State 1 represents grassland steppe with no invasive or exotic weed species. All the functional, structural groups are represented by one or more native species.
The Reference Community 1.1 is dominated by needle and thread. Sandy mostly has no shrubs and forbs are a minor component.
Reference State Community Phases:
1.1 Reference Needle and thread
Dominate Reference State Species: needle and thread
At-risk Communities:
All communities in the Reference State are at risk on invasion by cheatgrass. Cheatgrass seeds blow onto most sites annually awaiting an opportunity to colonize the site.
Description
State 2 Narrative:
State 2 represents sites dominated by invasive annual species and has crossed a biological threshold. As State 1 begins to unravel needle and thread declines while invasive grasses become more and more prominent. Virtually all the native functional, structural groups are missing in State 2.
Community Phases for State 2:
2.1 Annual Grass Cheatgrass
Dominate State 2 Species:
Annual grasses such as cheatgrass. Other common species can include Russian thistle, mustard, prickly lettuce and diffuse knapweed.
Description
State 3 Narrative:
State 3 represents a site that has been seeded to desirable grasses such as Siberian wheatgrass, crested wheatgrass and needle and thread. State 3 is stable if 0.8 plant per square foot or greater of the desired bunchgrasses is maintained.
Dominate Species for State 3:
Desirable seeded grass species
Community Phases for State 3:
3.1 Seeded Grass
Mechanism
T1 Result: shift from Reference State (all native species) to State 2 which is dominated by annual grasses. This transition occurs once the cover of needle and thread declines to less than 10 percent and invasive species cover is greater than 40 percent.
Primary Trigger: grazing pressure (heavy grazing, season long grazing or frequent late spring grazing) to needle and thread. In Washington, chronic season-long grazing caused more acres of State 2 than anything else. Repeated fire, another trigger, is a much more common event in south Central Washington than elsewhere.
Ecological process:
1. Colonization of invasive species: Cheatgrass seed blows onto most site annually. As opportunity presents itself, cheatgrass colonizes a site. Secondary trigger of colonization is soil disturbances (rodents, badgers), or a high moisture year causes a micro-burst of cheatgrass and is the principle means of colonization.
2. Expansion of invasive species: consistent defoliation pressure to needle and thread causes low vigor, low production of viable seed, fewer seedlings and reduced cover of needle and thread. As the grazing pressure continues, annual grasses become dominate.
Indicators: The occurrence of annual grasses on sites where there has been none. Decreasing vigor and cover of needle and thread and increasing cover of invasive annual species. Increasing distance between perennial species. Decreasing soil organic matter, soil water retention, limited water infiltration and percolation in the soil profile.
Mechanism
Recovery
R1 Result: shift from State 2 dominated by annual grasses to State 3 desirable seeded grasses. This soils on this site are highly calcareous. Species selection is a critical consideration.
This restoration transition does not occur without significant time and inputs to control weeds, prepare a seedbed, seed desirable species, and post-seeding weed control and management. This requires a commitment of two years or more for weed control. Care must be taken to maintain soil structure so that the seedbed has many safe-sites for the seed. Seed placement must be managed to achieve seed-soil contact at very shallow depth (about 1/8 inch is desired). Proper grazing management is essential to maintain the stand post-seeding.
The actual transition occurs when the seeded species have successfully established and are outcompeting the annual species for cover and dominance of resources.
Mechanism
T2 Result: Transition from State 3 seeded grass to State 2 annual grasses. This transition occurs when the desirable seeded grasses become minor to the dominant annual grasses.
Primary trigger: grazing pressure (heavy grazing intensity, season long grazing and frequent late spring grazing) to the seeded grasses reduce the vigor and density of desirable seeded grasses.
Ecological process: consistent defoliation pressure to desirable seeded grasses results in poor vigor, shrinking crowns and plant mortality. As the seeded grass community unravels, invasive annual grasses colonize the site and become more and more dominant with the loss of each bunchgrass.
Indicators: reduced cover and mortality of desirable species, increasing caps gaps between perennial species, increasing cover by annual grasses.
Model keys
Briefcase
Add ecological site groups and Major Land Resource Areas to your briefcase by clicking on the briefcase (
) icon wherever it occurs. Drag and drop items to reorder. Cookies are used to store briefcase items between browsing sessions. Because of this, the number of items that can be added to your briefcase is limited, and briefcase items added on one device and browser cannot be accessed from another device or browser. Users who do not wish to place cookies on their devices should not use the briefcase tool. Briefcase cookies serve no other purpose than described here and are deleted whenever browsing history is cleared.
Ecological site groups
Major Land Resource Areas
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.