Very Shallow

Description

State 1 Narrative:
The Reference State represents non-invaded communities composed of native species. Invasive annual grasses are not present. Very Shallow sites rarely burn, and in most cases, receives minimal grazing. This ecological site is the most stable ecological site on the landscape.

Reference Community 1.1 is the classic Very Shallow, dominated by Sandberg bluegrass with one or more low shrub species. The low shrub component may be stiff sage, low sage &/or one or more buckwheat low shrub species. So, Community 1.1 is mostly very stable. remaining in State 1 regardless of climate or management. Similarity Index scores are typically higher on Very Shallow than other ecological sites on the landscape.

Community 1.2 represents a community phase which is quite rare in MLRA 6. The species are native, but Sandberg bluegrass has a diminished presence and forbs are more prominent. Community 1.2 still has enough Sandberg bluegrass present, to shift back to reference community 1.1, given and improvement in grazing use by wildlife, feral horses and livestock.

Reference State Community Phases:
1.1 Reference Sandberg bluegrass – low shrub
1.2 Native forb – low shrub

Dominant Reference State Species:
Sandberg bluegrass and stiff sage, low sage &/or low shrub buckwheat species

At-risk Communities:
• All communities in the reference state are at risk of moving to State 2. The seed source of cheatgrass is nearby and blowing onto most sites annually
• Community 1.1 has a high Sandberg bluegrass cover and is thus, at low risk of moving to State 2, Forb-Annual Grass
• Community 1.2, the degraded native community, has low amount of Sandberg bluegrass cover and a high amount of forb cover, and is at considerable risk of moving to State 2

Submodel

Description

State 2 Narrative:
This state represents a shift from native grasses to a forb-annual grass dominated situation. The low shrubs usually remain. Most Very Shallow sites never cross the threshold into State 2. They stay at climax or near climax condition, as these sites generally receive limited grazing pressure and rarely burn.

State 2 is rare. The situation below has been witnessed on a couple of ridgetops west of Yakima on MLRA 6 sites. Chronic heavy grazing in the spring from migrating elk, feral horses or livestock caused the following:
• Near elimination of Sandberg bluegrass, resulting in
• A plant community dominated almost exclusively by annual forbs &/or annual grasses.
• Annual grasses were rare in the situations witnessed west of Yakima

Invasive annual grasses, which are common & frequently dominant on Loamy ecological sites, do not compete as well on Very Shallow sites. But a micro-burst of cheatgrass can occur. Cheatgrass seed blows onto Very Shallow sites annually. In a year with heavy snowfall and early spring rain, such as 2017, the site had far more moisture than the plant community can utilize. This is the opportunity for cheatgrass seed to germinate and produce a huge flush of cheatgrass plants. In following years when moisture is normal or below normal, cheatgrass seed will not germinate or make viable plants. So, these micro-bursts of cheatgrass tend to be episodic and mostly a temporary condition on Very Shallow sites.

However, the description above may not apply to Very Shallow sites on the High Prairie in Klickitat county or on the Swauk Prairie in Kittitas County. These prairie sites have been altered by heavy grazing pressure and may be dominated by cheatgrass, medusahead, ventenata or bulbous bluegrass. Lomatium or another native forb are prominent as well.

A reduction to Sandberg bluegrass cover allows annual grasses the opportunity to colonize and invade on a more permanent basis. Occasionally one will find minor amounts of scattered annual grasses on Very Shallow sites.

Heavy grazing use disrupts the soil surface and the moss-lichen layer via animal hooves, which in turn, causes loss of both soil structure and biological crust. When this happens site resistance to erosional forces are greatly diminished.

State 2 will likely have much less or much more pedestaling than the reference condition. Trampling by livestock or game animals can obliterate pedestals and terracettes. Or, erosion in water flow patterns can cause much more pedestaling than reference condition.

Submodel