Volcanic Ash Forest

Description

The Reference State consists of one community phase. It is a forest of low to medium height overstory with a nearly closed upper canopy. The lower, drier elevations of this ecological site have largely been converted to naturalized grassland. Based on remnant stands in this zone, mosses, liverworts, and epiphytic ferns are less abundant than in higher, wetter areas. It is likely that this lower zone originally had a different species composition as it graded into the drier ecological site below.

This state can transition into State 4 Timber Plantation by clearing and planting with introduced timber species. It transitions into State 2 Invaded Understory by weed invasion, which is accelerated by disturbance from domestic and feral ungulates. It transitions to State 5 Naturalized Grassland with Remnant Trees by mechanical clearing or gradual clearing by uncontrolled grazing and browsing by ungulates, followed by establishment of forage grasses or invasion by weedy introduced grasses.

Submodel

Description

This state consists of one community phase. It arises by invasion by introduced species of intact native forest (the Reference State) or, in some cases, of native overstory stands from which the original understory has been cleared. Native species are unable to regenerate in the highly competitive understory of introduced plants and eventually die out. With time, large introduced tree species will emerge to replace the native overstory trees and form a new overstory. When this last step has occurred, the site will have transitioned to State 3 Invaded Overstory and Understory.

Disturbance of the soil and direct damage to native understory plants by introduced ungulates, particularly pigs and cattle, will speed the transition to this state by killing native plants and by creating better germination sites for introduced species.

Restoration to the Reference State or a facsimile of it is possible by fencing the site, removing all ungulates, applying herbicides, and replanting native species when needed. Restoration efforts will be affected depending on the degree of invasion by introduced species and by the particular species that have invaded the site. Long term weed management and fence maintenance will be necessary.

Submodel

Description

This state is comprised of one plant community dominated by introduced species in both the overstory and understory. Understory vegetation usually is very sparse to nonexistent. Remnant individuals of a few native species may persist. This state might be considered a dead end as far as further succession. Mechanical clearing followed by establishment of introduced timber species would bring a transition to State 4 Timber Plantation; mechanical clearing followed by establishment of introduced forage specie would bring a transition to State 6 Naturalized Grassland.

Submodel

Description

This state consists of one community phase, which is a plantation of introduced timber tree species that have been established on forest or grazing lands. With proper management, it is not susceptible to unplanned transitions or restorations to other states.

Submodel

Description

This state consists of three grassland community phases that have an open canopy of native trees. These phases are maintained by grazing, which keeps preferred species from becoming too rank, and adequate recovery periods, which ensure vigor and cover of preferred species. High production of preferred grass species and extensive cover allow for increased soil moisture retention, vegetative production, and overall soil quality. These factors are degraded by grazing practices that result in loss of preferred grass species leading to increase in less desirable grasses, weed invasion, and an increase in the extent of bare soil.

Community phase 5.1, when subjected to continuous grazing that does not allow the preferred forage species to recover from defoliation, shifts to Community phase 5.2, which is dominated by lower value grass species but contains enough cover of preferred forages to allow for a shift back to Phase 5.1 with prescribed grazing. Longer-term continuous grazing leads to Community Phase 5.3, which consists of low value grass species and increasing cover of weedy shrubs and tree saplings. Improvement of this phase requires weed control followed by prescribed grazing.

Submodel

Description

This state consists of three grassland community phases with little or no tree overstory. These phases are maintained by grazing, which keeps preferred species from becoming too tall, and adequate recovery periods, which ensure vigor and cover of preferred species. High production of preferred grass species and extensive cover allow for increased soil moisture retention, vegetative production, and overall soil quality. These factors are degraded by grazing practices that result in loss of preferred grass species leading to increase in less desirable grasses, weed invasion, and an increase in the extent of bare soil.

Community phase 6.1, when subjected to continuous grazing that does not allow the preferred forage species to recover from defoliation, shifts to Community phase 6.2, which is dominated by lower value grass species but contains enough cover of preferred forages to allow for a shift back to Phase 6.1 with prescribed grazing. Longer-term continuous grazing leads to Community Phase 6.3, which consists of low value grass species and increasing cover of weedy shrubs and tree saplings. Improvement of this phase requires weed control followed by prescribed grazing.

Submodel