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 11. 1.2 Shortgrass Prairie Community

This community phase occurs as the taller, more productive grasses are slowly replaced by short grasses and forbs. Threeawn species (Aristida spp.), hooded windmillgrass (Chloris cucullata), tumble lovegrass (Eragrostis sessilispica), fall witchgrass (Digitaria cognate), grass bur (Cenchrus spinifex), thin paspalum (Paspalum setaceum), hairy grama (Bouteloua hirsute), and Rio Grande bristlegrass (Setaria reverchonii subsp ramiseta) are common grass species that increase in abundance. The annual forb and grass community is highly variable but responds quickly to rainfall events. Some common forbs include palafoxia (Palafoxia spp.), snake cotton (Froelichia floridana), annual and perennial crotons (Croton spp.), and viperina (Zornia bracteata). Mesquite (Prosopis glandulosa) and hogplum (Colubrina texensis) are the first woody species to establish.

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 (<a class="species-link" href="https://plants.usda.gov/core/profile?symbol=PECI" target="_blank" title="Open in plants.usda.gov"><i>Pennisetum ciliare</i></a>) and Kleberg bluestem (<a class="species-link" href="https://plants.usda.gov/core/profile?symbol=DIAN" target="_blank" title="Open in plants.usda.gov"><i>Dichanthium annulatum</i></a>), and tanglehead (<a class="species-link" href="https://plants.usda.gov/core/profile?symbol=HECO10" target="_blank" title="Open in plants.usda.gov"><i>Heteropogon contortus</i></a>). 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 14. 2.1 Savannah Community

Figure 15. 2.1 Savannah Community

This community phase is a complex of grasses, forbs, and shrubs. The woody component has established and grown tall enough to survive periodic fire. Research in South Texas has shown that different plant species are recruited into the plant community at different stages of succession. Mesquite and hogplum are commonly the first to appear followed by lime pricklyash (Zanthoxylum fagara), granjeno (Celtis ehrenbergiana), brasil (Condalia hookeri), Texas persimmon (Diospyros texana), catclaw acacia (Acacia greggii), lantana (Lantana urticoides), leather stem (Jatropha dioica), and prickly pear (Opuntia engelmannii). As brush mottes develop, desert yaupon (Schaefferia cuneifloia), elbowbush (Forestiera pubescens), wolf berry (Lycium berlandieri), coma (Sideroxylon celastrinum), and lotebush (Ziziphus obtusifolia) will also begin to appear. Blackbrush acacia (Acacia rigidula) generally occurs within proximity of the soils associated with the Red Sandy Loam ecological site. The brush component of this ecological site tends to form discrete mottes with single or multiple species. This phase can be stable for more than 20 years before brush mottes coalesce and form large continuous areas. The herbaceous component can be similar in composition to the Grassland State, but grass production will continue to decrease while bare ground and forbs increase. In this phase introduced grasses like guineagrass (Urochloa maxima), and buffelgrass can increase and invade the native plant community. Tanglehead is another species that will dominate large areas under the right circumstances. Bare ground in this phase can typically range from 5 to 25 percent and gaps in the brush canopy range from 2 to 65 feet.

Community 2.2
Shrubland

Figure 18. 2.2 Shrubland Communtiy

Figure 19. 2.2 Shrubland Communtiy

The woodland phase of the brush state develops as brush species coalesce into large scattered mottes. A continuous brush canopy develops within each motte and the plant composition is almost exclusively composed of woody species. Mottes tend to be isolated “islands” within the Savannah Phase (2.1) and will not cover large areas of the landscape. Herbaceous production is very low and will include plants like three awn species, hooded windmillgrass, and Rio Grande bristlegrass. Although mesquite is very common, other co-dominant species include hog plum and catclaw acacia. Different sub-canopy brush species that will typically make up less than 15 percent of the canopy cover include brasil, lime pricklyash, prickly pear, Texas persimmon, and granjeno.

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 22. 3.1 Planted Pasture Community

This plant community is not common and is hard to maintain, but can be developed. Introduced grasses like Wilman’s lovegrass and buffelgrass have been used by land managers to create pastures. 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. For maintenance, herbicides must be used to control woody seedlings that seek to invade as soon as the pasture is established. Not only is there a long-lived seed source of mesquite and other woody species, additional seed are brought in by grazing animals and domestic livestock.

Community 3.2
Go Back Land

Figure 25. 3.2 Go Back Land Community

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

Planted Pasture

Go Back Land

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

Go Back Land

Planted Pasture

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. An on-site evaluation should be made before any mechanical preparation, because the depth of the soil to a petrocalcic layer varies. 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 ecological site as pastureland. Once in the Mixed Brush Complex (2), mechanical brush control will be necessary. Many species of brush 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. An on-site evaluation should also be made before any mechanical method is used, because the depth of the soil to a petrocalcic layer varies. After the land has been cleared and an appropriate seedbed prepared the land can be planted to introduced grasses for pasture.

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.