State 1
Grassland

Community 1.1
Native Mid/Shortgrass Prairie

Because of a lack of reference communities, the interpretive information for this plant community is derived from previously developed range site descriptions and professional consensus of range trained field staff. This plant community is a productive mid/shortgrass prairie with a high diversity of forb species and occasional woody plants. The plant structure is maintained by a grazing and fire regime which recycles organic matter and nutrients from standing herbaceous material and prevents woody species from establishing dominance on the ecological site. This plant community is resistant to change and can persist through periodic droughts and other types of disturbance. On the other hand, it is not very resilient if herbaceous production and ground cover are dramatically reduced on a regular basis.

Community 1.2
Shortgrass Prairie

Figure 10. 1.2 Shortgrass Prairie Community

Heavy grazing or absence of fire results in establishment of woody plant seedlings and a shift from dominance by midgrasses to a community dominated by shortgrasses. Plants that will increase in dominance include threeawn species (Aristida), red lovegrass (Eragrostis secundiflora), and hooded windmillgrass (Chloris cucullata). An overstory will develop consisting of 5 to 20 percent canopy cover of mesquites (Prosopis glandulosa) and associated woody plants under three feet tall. The forb community is highly variable. Bare ground in this phase will typically range from 10 to 30 percent with total litter cover ranging from 50 to 70 percent. Gaps in the brush canopy can range from 1 to greater than 200 feet.

Pathway 1.1A
Community 1.1 to 1.2

This pathway represents a slow but continuous reduction in herbaceous plant production which affects many different ecological processes. Drought and grazing pressure are the main drivers for this transition, which in turn affect the fire regime. The larger bunchgrass species lose dominance and are gradually replaced with short grasses and forbs as litter cover is reduced and bare ground increases.

Pathway 1.2A
Community 1.2 to 1.1

Grazing management is key to restoring the Mid/Shortgrass Prairie Community (1.1). Sustainable grazing keeps pressure off target grass species and allows enough fine fuel to build up and support prescribed burns. In this phase fire is an effective tool that can be used to suppress woody plants and promote the grass and forb community. A prescribed burn plan with the goal of suppressing brush in the grassland state should initially be designed to have burns every three to five years. In some cases, burning may not be feasible because of weather conditions or ranch management issues. Currently, prescribed burns may also have unintended results like increased buffelgrass (Pennisetum ciliare) and Kleberg bluestem (Dichanthium annulatum), and tanglehead (Heteropogon contortus). In these cases, mechanical brush control practices that remove the rootcrown of re-sprouting species or herbicide that can kill target species without ground disturbance are also effective. An integrated brush management plan which utilizes fire in combination with mechanical and chemical treatments can be very effective in suppressing brush encroachment.

State 2
Mixed Brush Complex

Community 2.1
Savannah

Figure 13. 2.1 Savannah Community

Elimination of fire results in a transition from the Grassland state (1) to the Mixed Brush Complex (2) with 20 to 70 percent woody cover. Brush management and implementation of proper grazing management are required to cause a transition back to the Grassland State. This community is dominated by mesquite, but brasil (Condalia hookeri), lotebush (Ziziphus obtusifolia), granjeno (Celtis ehrenbergiana), and armagosa (Castela erecta) are also common. Bare ground in this phase will typically range from 1 to 30 percent with total litter cover ranging from 50 to 70 percent. Gaps in the brush canopy can range from 1 to 75 feet.

Community 2.2
Shrubland

Figure 16. 2.2 Shrubland Community

The Shrubland develops as brush species coalesce into large mottes limiting herbaceous production. A continuous brush canopy develops within each motte and the plant composition is almost exclusively composed of woody species. Herbaceous production is very low and will include plants like threeawn species, hooded windmillgrass, and plains bristlegrass (Setaria vulpiseta). Although mesquite is very common on this site, and can potentially create greater than 50 percent of the brush canopy cover, other co-dominant species include granjeno and lime prickly ash (Zanthoxylum fagara). Different sub-canopy brush species that can individually compose 0 to 30 percent of the canopy cover include brasil, armagosa, lotebush, and prickly pear (Opuntia engelmannii). Bare ground in this phase will typically range from 1 to 20 percent with total litter cover ranging up to 99 percent. Gaps in the brush canopy can range from 2 to 45 feet.

Pathway 2.1A
Community 2.1 to 2.2

Savannah

Shrubland

The transition from Savannah (2.1) to Shrubland (2.2) occurs slowly over time and is highly dependent on weather, ground cover, competition from grasses and seed dispersal. Because there are so many factors, it is difficult to determine which areas are most susceptible to woody plant encroachment. This plant community can have a large amount of bare ground and relatively low amounts of herbaceous production, putting it constantly at risk of brush encroachment. The Savannah Phase’s stability is due to the low water holding capacity of the soil surface, which may make it difficult for woody plants to germinate and survive in open areas with no ground cover.

Pathway 2.2A
Community 2.2 to 2.1

Shrubland

Savannah

The Shrubland Community (2.2) is distinguished from the Savannah Community (2.1) by the increase in woody plant canopy cover, which negatively affects herbaceous production. Extreme dry weather can cause plant mortality and a decrease in woody cover, but this is a cyclic process and woody cover density can recover. Mechanical brush control will be necessary to restore the Savannah Community (2.1), because grazing and fire will not have large impacts on mature brush mottes.

State 3
Converted Land

Community 3.1
Planted Pasture

Figure 19. 3.1 Planted Pasture Community

Farming is not recommended on the Loamy Sand ecological site because of a low water holding capacity and high erosion potentials of the soil. However, the site is sometimes cultivated and used for production of watermelons and other crops. Grass pastures may also be developed with introduced grasses but are hard to maintain. Inputs such as herbicide and adequate precipitation are necessary to maintain high productivity. Now, because of the availability of seed, landowners can also replant with native species. To maintain this seeded state, herbicides must be used to control woody seedlings that invade as soon as the pasture is established. Not only is there a long-lived seed source of mesquite and other woody species, additional seeds are brought in by grazing animals and domestic livestock.

Community 3.2
Go Back Land

This community develops after land has been planted to pasture and then left to fallow without management inputs. It can also develop after a mechanical brush management practice has been applied during poor weather conditions or not followed up with appropriate management practices. It is typified by low plant diversity, the dominance of woody species, very little herbaceous grass production, high amounts of annual forbs, and bare ground. Because of the seed bank present in the soil, and the constant addition of new seed from grazing/browsing animals and seed eating birds, re-infestation of woody seedlings can happen in less than five years. The production and plant community structure are highly variable in the Go Back Land Community (3.2).

Pathway 3.1A
Community 3.1 to 3.2

The transition from Planted Pasture (3.1) to Go Back Land (3.2) occurs when pastures are left to fallow without brush management. Woody species gain a competitive advantage and a low diversity plant community typically develops.

Pathway 3.2A
Community 3.2 to 3.1

After an area has reverted to Go Back Land (3.2), land managers may want to utilize the ecological site as pasture again. From a species diversity and wildlife habitat perspective, it is usually a good idea to reclaim an area that has already been manipulated in the past, instead of clearing another, more species rich, part of the management area. Once in this phase, mechanical brush control will be necessary, and a seed bed will need to be prepared to replant introduced grasses for pasture.

Transition T1A
State 1 to 2

The transition from the Grassland State (1) to the Mixed Brush Complex (2) can happen relatively quickly if conditions favor woody plant seedlings. The shortgrass plant community is an at risk phase of the Grassland State. As bare ground increases and competition from grasses decrease, woody plants have a chance to germinate. Within as little as five years after seedling establishment, mesquite may grow too large to be effectively managed with grazing or fire, especially if the fine fuel needed to carry an effective burn is not being produced. Other brush species native to this ecological site will take significantly longer to grow out of the fire control range, but mesquite acts as a nursery plant which speeds up the transition process. Discrete mottes of brush will begin to develop as the woody plants grow, pushing the plant community into a Mixed Brush Complex (2).

Transition T1B
State 1 to 3

Land managers may want to utilize this ecological site as pastureland. After the land has been cleared and an appropriate seedbed prepared, the land can be planted to introduced grasses for pasture.

Restoration pathway R2A
State 2 to 1

Land managers may want to restore this ecological site to the Native Grassland State (1). Once in the Mixed Brush Complex (2) mechanical or chemical brush control will be necessary to make the transition. The restoration process is heavily dependent on favorable weather and patience. Land managers can plant native seed to speed up restoration efforts or can rely on seed that is already in the soil. Grazing pressure on restoration sites should be deferred for a minimum of one growing season, but it is often necessary to defer livestock grazing completely or carefully graze for years before the desired plant community can develop.

Transition T2A
State 2 to 3

Land managers may want to utilize this site as pastureland or more rarely cropland. Once in the Mixed Brush Complex (2), mechanical brush control will be necessary. Many species of brush on this site are capable of re-sprouting after top removal, which is an important factor to consider when deciding how to clear the land to plant pasture. After the land has been cleared and an appropriate seedbed prepared, the land can be planted to crops such as watermelon, sorghum, or introduced grasses for pasture.

Restoration pathway R3A
State 3 to 1

The transition from the Converted Land State (3) to the Grassland State (1) will take time and patience. In the seeded phase, Planted Pasture (3.1), if practices such as fertilizer application and weed control are stopped, prescribed grazing is applied, woody seedlings are managed, and prescribed burning is applied, this ecological site will begin the reversion back to the Grassland State (1) as seedlings of native species become established. Introduced grass species are very resilient and competitive. They can maintain dominance in a pasture for a very long time after they are planted even without careful management. In these cases, management practices such as disking or applying herbicide to kill or suppress introduced species will be necessary to achieve the transition from an introduced pasture to a native pasture. This transition may occur very slowly because introduced grasses will remain competitive and will probably always be present. This transition may also require brush management practices and the reintroduction of desirable native species through range planting.

Transition T3A
State 3 to 2

In time, this ecological site will revert to the Mixed Brush Complex (2) on its own, but usually this timeline is impractical for landowners. Prescribed grazing along with various brush management practices will be necessary to achieve this transition and allow the mixed brush community to develop. This phase is very unproductive for herbaceous plants and it could take years for desirable plant species to begin to reestablish.