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 State Community Phases:
1.1 Reference Sandberg bluegrass – low shrub
1.2 Forb – low shrub Native forbs with low shrub

Dominant Reference State Species:
Sandberg bluegrass and stiff sage &/or other low shrub Eriogonum 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 lower risk of moving to State 2, Forb-Annual Grass
• Community 1.2, has less 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 the ecological changes that occur when there is a shift from dominance by perennial native grasses to forbs or annual grass dominance in the herbaceous layer. The shrub components generally remain in the overstory.

Most Very Shallow sites never cross the threshold into State 2 as they are not attractive to grazing animals and rarely burn (limited forage values and surface rocks). The exception being chronic heavy grazing in the spring from migrating elk, feral horses or livestock. As the cover of Sandberg bluegrass significantly declines the site becomes open to invasion by invasive annuals, however.

 
Invasive annual grasses, which are common & frequently dominant on adjacent Loamy ecological sites, do not often compete as well on Very Shallow sites. However, the cheatgrass seed blows onto Very Shallow sites annually and can become a minor component. In a year with heavy snowfall and early spring rain, such as 2017, the site had far more moisture that the plant community could utilize. This is the perfect opportunity for cheatgrass seed, which is capable of rapid germination and growth to establish in significant amounts across the site. In following years when moisture is normal or below normal, native species will utilize most of the available moisture and cheatgrass seed will not germinate or make viable plants. Therefore, in most cases, these micro-bursts of cheatgrass tend to be episodic and mostly a temporary condition on Very Shallow sites.

However, due to long term disturbances and higher precipitation, Very Shallow sites in the Goldendale Prairie portion of MLRA 8 are now dominated by cheatgrass, medusahead, ventenata or bulbous bluegrass. Sites have been significantly impacted by heavy grazing pressure from livestock that have removed much of the native grass components, leaving niches for these invasive annuals to take hold. Native forbs such as Lomatium may be prominent, but the grass component has shifted completely.

A reduction to Sandberg bluegrass cover allows annual grasses the opportunity to colonize and invade on a more permanent basis. 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 as well.

State 2 may exhibit either a significant decrease in pedestaling due to the lack of bunchgrass cover and heavy use trampling by ungulates, or there will be a significant increase in pedestaling due to increased erosion from water flows around the remaining bunchgrasses.

Community Phases for State 2:

Community Phase 2.1: dominated by native forbs and/or invasive annual grasses. Forbs which increase in the altered conditions and are competitive with invasive grasses, can include lomatium, fleabane, willow herb, yarrow and onion. Typical invasive grasses may include annual bromes, medusahead and sixweeks fescue.

Submodel