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 staff. This plant community is a productive mid/short grass prairie with a mix of occasional woody plants. This plant structure is maintained by infrequent grazing and fire regime which recycled organic matter and nutrients from standing herbaceous material and prevented 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

This community phase occurs as the taller, more productive grasses are slowly replaced by shortgrasses and forbs. Threeawn species (Aristida spp.), hooded windmill grass (Chloris cucullata), tumble lovegrass (Eragrostis sessilispica), fall witchgrass (Digitaria cognate), grass bur (Cenchrus spinifex), thin paspalum (Paspalum setaceum), hairy grama (Bouteloua hirsute), and knotgrass (Setaria reverchonii subsp firmula) increase in abundance. The annual forb and grass community is highly variable but responds quickly to rainfall events. Some common forbs include annual and perennial crotons (Croton spp.), slender evolvulus (Evolvulus alsinoides), and Indian mallow (Abutilon fruticosum). Mesquite (Prosopis glandulosa), whitebrush (Aloysia gratissima), and hogplum (Colubrina texensis) are commonly the first woody species that begin to establish. These soils will form a crust as bare ground increases causing less water infiltration after rainfall events and a decrease in herbaceous productivity and seedling germination.

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 affects the fire regime. The larger bunchgrass species lose dominance and are gradually replaced with shortgrasses 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 such as the increase of species like buffelgrass (Pennisetum ciliare) and Kleberg bluestem (Dichanthium annulatum). 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 effective. An integrated brush management plan which utilizes fire in combination with mechanical and chemical treatments can suppress brush encroachment.

State 2
Mixed Brush Complex

Community 2.1
Savannah

Figure 13. 2.1 Savannah Community

Figure 14. 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 areas of South Texas have shown that different plant species are recruited into the plant community at different stages of succession. Mesquite, whitebrush, and hogplum are commonly the first to appear. Blackbrush acacia (Acacia rigidula), catclaw acacia (Acacia greggii) ,and rarely wherry mimosa (Mimosa texana) can also be the primary brush species. Other species that will fill in the brush canopy include lime pricklyash (Zanthoxylum fagara), granjeno (Celtis ehrenbergiana), brasil (Condalia hookeri), Texas persimmon (Diospyros texana), 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 begin to appear. The brush component will eventually form continuous mottes that will cover large areas. The herbaceous component can be similar to the grassland state, but grass production will continue to decrease while bare ground will increase. In this phase, introduced grasses like buffelgrass and Kleberg bluestem can increase and invade the native plant community. Bare ground in this phase will typically range from 1 to 30 percent, with total litter cover ranging up to 65 percent. Gaps in the brush canopy can range from 5 to 90 feet with an average brush canopy gap of about 32 feet.

Community 2.2
Shrubland

Figure 17. 2.2 Shrubland Community

Figure 18. 2.2 Shrubland Community

Figure 19. 2.2 Shrubland Community

The Shrubland Community develops as brush species coalesce into large mottes and severely limit herbaceous production. These mottes form a continuous brush canopy that can expand to cover vast areas and are exclusively composed of woody species. Herbaceous production is very low and will include plants like threeawn species, hooded windmillgrass and Rio Grande bristlegrass. Although mesquite is very common on this ecological site, other co-dominant species include hog plum, catclaw acacia, blackbrush acacia, and rarely wherry mimosa. The sub-canopy is very diverse but the most common brush species are granjeno, brasil, lime pricklyash, prickly pear, whitebrush, lotebush, guayacan, and armagosa. Bare ground in this phase will typically range from 1 to 15 percent with total litter cover ranging from 30 to 97 percent. Gaps in the brush canopy can range from 5 to 50 feet with an average brush canopy gap of about 15 feet.

Pathway 2.1A
Community 2.1 to 2.2

Savannah

Shrubland

The transition from Savannah to Shrubland can occur quickly depending on seed dispersal and the timing of rain, but is also highly dependent on ground cover and competition from grasses. 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.

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 will 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

Buffelgrass is the main species that is used by land managers to develop grass pastures. 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 pasture, 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 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 left to fallow without management. It can also develop after a mechanical brush management practice has been applied during poor weather conditions. It is typified by low plant diversity, with mesquite and prickly pear dominating the woody species, very little herbaceous grass production, and high amounts of 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 a relatively short time period of less than five years. The production and plant community structure are highly variable in the Go Back Land (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 the Go Back Land phase (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 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 grasses for pasture.

Transition T1A
State 1 to 2

The transition from the Grassland State (1) to the Mixed Brush Complex (2) is relatively slow, in part because of low rainfall received in this area. This phase can be stable for more than 15 years before brush species are able to establish. As bare ground increases and competition from grasses decrease, woody plants have a chance to germinate.

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 back to the Grassland State. 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 native 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 on this ecological 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 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 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 restoration back to the Grassland State (1. 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. 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 re-introduction of desirable native species through range planting.

Transition T3A
State 3 to 2

If the Go Back Land Community (3.2) is left alone, eventually the woody plants will create a moderate to heavy canopy. At this point, the desired understory grasses, forbs, and/or crops will be shaded out and the site will transition into a Mixed Brush Complex (2).