Subirrigated Sands

Description

This state represents the natural range of variability that dominates the dynamics of this ecological site. Plant community phases occurring within this state are diverse, stable, productive, and well adapted to the Northern Great Plains. The primary disturbance mechanisms for this site in the reference conditioned include frequent fire and grazing by large herding ungulates. Timing of fires and grazing, coupled with weather events, dictated the dynamics that occurred within the natural range of variability.

Colonization of the site by exotic plants, mainly cool-season grasses such as Kentucky bluegrass, quackgrass, and/or smooth brome can cause the site to transition to the State 2: Native/Invaded Site. A transition to State 3: Invaded State can be expected unless a prescribed grazing and/or prescribe burning program is implemented.

Submodel

Description

This state is very similar to the Reference State but now supports minor amounts of exotic plants. This state is still dominated by native warm-season and cool-season grasses; but exotic species, typically the cool-season grasses Kentucky bluegrass, smooth brome, and/or quackgrass are now present in all community phases of the state. Annual production can vary considerably, in part due to the extent of invasion by cool-season grasses, but may be in the range of 3800-4550 pounds per acre with the exotic cool-season grasses contributing between 16-30%.

These exotic cool-season grasses have been particularly and consistently invasive under extended periods of non-use and no fire. To slow or limit the invasion of these exotic grasses, it is imperative that managerial options (e.g. prescribed grazing, prescribed burning, other) be carefully constructed and evaluated with respect to that objective. If management does not include measures to control or reduce these exotic cool-season grasses, the transition to State 3: Invaded State should be expected.

Submodel

Description

This state is the result of invasion and dominance by exotic plants, typically the cool-season grasses (Kentucky bluegrass, smooth brome, and/or quackgrass). These exotic cool-season species often form monotypic stands and, as a result, plant diversity is often markedly reduced and peak production is restricted to late spring/early summer. With the invasion of Kentucky bluegrass or smooth brome this state is often characterized by an increasing thatch layer that effectively blocks introduction of other plants into the site. Annual production can vary considerably, in part due to the extent of invasion by cool-season grasses but may be in the range of 3000-5000 pounds per acre with the exotic cool-season grasses contributing between 59-86%.

Once the state is well established, even drastic events such as high intensity fires driven by high fuel loads of litter and thatch will not result in more than a very short-term reduction of these two species. These events may reduce the dominance of these exotic sodgrasses but, due to the large amount of rhizomes in the soil, there is no opportunity for the native species to establish and dominate before the exotic sodgrasses rebound and again dominate the site.

Submodel

Description

This community phase is highly variable depending on the level and duration of disturbance related to the T5A transitional pathway. In this MLRA, the most probable origin of this phase is plant succession following cropland abandonment. This plant community will initially include a variety of annual forbs and grasses, some of which may be noxious weeds needing control. However, over time exotic cool-season grasses such as Kentucky bluegrass, smooth brome, and/or quackgrass come to dominate the site. Associates include western snowberry, wild rose, common dandelion, Canada goldenrod, common yarrow and Canada thistle.

Description

This state is the result of annual cropping.