State 1
Reference

This state is considered to be representative of the natural range of variability under per-Euro settlement conditions. It is characterized by a warm-season, tallgrass savannah with scattered trees. Community phase changes are primarily driven by wildfire, grazing, and climatic fluctuations.

Community 1.1
Tall Grass Savannah

Figure 10. Reference Plant Community, Kendall County.

Figure 11. Clay loam ecological site. Kendall County, 1976

Figure 12. Clay Loam ecological site. Kendall County, Texas

Figure 13. Clay Loam ecological site. Bexar County, Camp Bull

This is the reference or interpretive community for the site. The description is based on early range site descriptions, clipping data, the professional consensus of experienced range specialists, and analysis of field work. Elm and hackberry trees occur along small streams, and Texas live oak trees or motts are widely scattered. Texas live oak can exist as both a tree and as a mott depending upon fire frequency or other disturbance as it is a vigorous root sprouter. Some juniper may occur depending upon the last fire. Estimated vegetative composition by weight is 85-90 percent grass, 5-10 percent forbs, 2-6 percent shrubs, and <2 percent trees. Total canopy cover of woody species is less than 5 percent. Little bluestem dominates the herbaceous plant community. Indiangrass and big bluestem are subdominants and may be locally dominant. Switchgrass and eastern gamagrass occurred in small quantities. Sideoats grama, Texas wintergrass, Texas cupgrass (Eriochloa sericea), silver (Bothriochloa saccharoides), and pinhole bluestem (Bothriochloa barbinodis var. perforata), vine mesquite (Panicum obtusum), and tall/meadow dropseed (Sporobolus compositus) are also prevalent but in lesser amounts. The site grows an abundance of palatable forbs and legumes such as Engelmann daisy (Engelmannia peristenia), orange zexmenia (Wedelia hispida), velvet bundleflower (Desmanthus velutinus), and trailing wildbean (Strophostyles helvola). This plant community is very stable and can withstand short term droughts although production will fluctuate accordingly. If the site is abused by overgrazing of the site with cattle, a reduction of the more palatable tall and mid grasses, forbs, and legumes will occur. Sideoats grama, Texas wintergrass, silver and pinhole bluestem, and buffalograss (Bouteloua dactyloides) will increase. Texas wintergrass, along with a small amount of wildryes (Elymus spp.), often dominates the site and furnishes considerable cool-season forage. The cool season plants will also be more prominent when abundant fall rains occur. Fire on a 5- to 10-year frequency will help suppress shrubs and add to the cycling of minerals and nutrients. Fires prevent excessive buildup of litter. Research on the effects of fire on soil organisms reveal complex results and are ecosystem dependent. Soil fauna may decrease following a burn if the burn leaves the soil bare and not insulated (Wright, 1982). It is anticipated that a burn on this site, leaving some litter on the soil, may initially depress soil fauna but then experience an increase following a burn mainly because the sun warms the ground quicker. This leads to more rapid nutrient cycling and increased production and quality. In general, if burning follows historic fire return intervals, the litter and soil fauna will be sustainable (Scifres, 1980). Grazing has a dual effect in maintaining this grassland. Grazing assists in nutrient cycling by digesting coarse grasses and depositing the digested plants through manure back to the soil surface. However, overgrazing can damage the plant community, create bare ground, and remove any opportunity for burning. Wildlife species such as birds and small mammals as well as livestock transport a variety of seeds onto the site. Shrubs will begin to establish under perches and cover for wildlife which is a place for new seedlings to establish. Once this begins to happen, the community is increasingly at risk of change. The plant community can be restored if an integrated regime of fire, maintenance brush, and proper grazing is completed. If these disturbances are not present, the 1.1 Tallgrass Savannah plant community will shift to the 1.2 Mid/Tallgrass Savannah plant community. This is within a normal range of variability for this site but if left long enough without the disturbances, the 1.2 Mid/Tallgrass Savannah plant community will transition into the Shrubland community (3) over time. If mechanical or chemical brush management were applied successfully, this community could also exist as an open, native, tallgrass prairie until the shrubs/trees inevitably reestablish. Continued mechanical or chemical suppression treatments would be needed in this case.

Community 1.2
Mid/tallgrass Savannah Community

Figure 16. . Clay Loam ecological site. Bexar County

Figure 17. Clay Loam ecological site. Bexar County

The data for this plant community comes from the analysis of field data along with professional consensus of experienced range trained individuals. This plant community occurs with yearlong grazing by large herbivores without the application of fire or brush management practices. However a threshold has not been crossed. With management, this community will remain very similar to the reference plant community. It represents the variability within the plant community that fluctuates from events like short term droughts or heavy grazing. Defoliation reduces energy for tall grasses and they are reduced in the plant community. This reduction in tall grasses allows increases of mid grasses such as sideoats grama, tall/meadow dropseed, plains lovegrass, and woody plants such as mesquite, juniper, and pricklypear. Cedar elm (Ulmus crassifolia), bumelia (Sideroxylon lanuginosum), and hackberry also start to increase in density and stature. Texas wintergrass and cedar sedge increases as brush canopy increases. They are shade tolerant and most of their growth occurs during the cool season when brush has lost its leaves. This plant community consists generally of a 5 to 15 percent canopy of woody plants. The hydrologic cycle is basically intact although the shift to cool season plants and more shrubs and trees will change the time of year soil moisture is used and increases some losses through entrapment. The soil is intact and stable relative to erosion. The Mid and Tallgrass Prairie Community (1.2) can revert back to a plant community very similar to the Reference Plant Community (1.1) as there are sufficient remnants of tall grasses and forbs for a response. An integrated approach using tools such as selective brush management, prescribed burning, and/or prescribed grazing is needed to maintain this community or restore it to the Reference Plant Community (1.1) if that is the goal. Deferment from grazing alone will not fully shift this plant community back to the Reference Plant Community (1.1) because of the increase of woody plants and the canopy that fosters cool season plants. However, deferment does preserve fuel load that can be used for prescribed burning to help maintain the plant community. Without brush management, prescribed burning, and/or prescribed grazing, this plant community would continue to shift toward the Short and Midgrass Community (2) or Shrubland Community (3).

Pathway 1.1A
Community 1.1 to 1.2

Tall Grass Savannah

Mid/tallgrass Savannah Community

Continuous season-long grazing at moderate to heavy stocking rate can suppress tall grasses. This can be a short term situation within the natural variation of the community. Removal of fire and the lack of brush management, as well as adverse weather, contribute to the change in the 1.1 plant community to the 1.2.

Pathway 1.2A
Community 1.2 to 1.1

Mid/tallgrass Savannah Community

Tall Grass Savannah

Restoring ecological processes such as prescribed grazing and prescribed fire aid in the recovery. Integrated brush management such as Individual Plant Treatment will also speed the restoration.

State 2
Shortgrass/Tree State

This state is characterized by a shift the dominant functional and structural groups along with changes in hydrologic cycling. Cool-season herbaceous species dominate the understory and runoff, infiltration, and soil moisture are impacted by increased canopy of woody species.

Community 2.1
Short/midgrass Savannah Community

Figure 20. Clay Loam Site, Blanco co.

Figure 21. Clay Loam ecological site. Bexar County

Figure 22. Clay Loam ecological site. Kendall County

Figure 23. Clay Loam ecological site, Krum Soil

The description for this plant community is derived from analysis of limited field data and the professional consensus of range trained individuals. The Shortgrass/Tree Community (2.1) consists of short and midgrasses with 15 to 30 percent overstory canopy of woody plants. It generally has a savannah-like appearance and is low on herbaceous plant diversity. As this community ages, brush canopy along with grasses such as Texas wintergrass, threeawn, and annuals continue to increase. Warm-season perennial tall grasses such as Indiangrass and switchgrass have all but disappeared as have many of the warm season mid grasses such as sideoats grama and plains lovegrass. Continuous abuse by mixed classes of domestic livestock has facilitated the shift. Abusive grazing has suppressed the original plants and also removed any fuel loading that would support a prescribed burn. Subsequently, the energy flow now is transformed into the overstory of woody plants and the cool-season plants and small shrubs in the understory. Some rainfall is trapped in the foliage of the overstory and evaporates but some also reaches the soil via stem flow. This stem flow enriches the Texas wintergrass and sedges that occupy the understory. Many times the interspaces in the canopy openings are occupied by curly mesquite, buffalograss, and other short grasses. During drought conditions, these interspaces can become bare and providing the opportunity for some surface movement of soil and increased runoff. Much of the forb population is cool-season annuals such as plantain (Plantago spp.) and common broomweed (Amphiachyris dracunculoides). If the management goal is to restore this plant community back to something resembling the reference community, reduction of the canopy of woody plants is needed and possibly reintroduction of seeds representative of the reference plant community. A field investigation is needed to evaluate the necessity for seeding although seeding can speed up the recovery and increase diversity. Tools that restore the restore the energy flow back to these plants and restore the hydrologic cycle include an integrated approach using brush management, fire, and prescribed grazing. It is possible to restore this plant community to something similar to the reference plant community but very difficult if not impossible to fully restore because of lost plant species having limited or no seed source in the market place. It will take many years to fully restore the soil health back to the reference condition. Even though this plant community is very stable, over time other small shrubs and cactus will populate the understory being brought to the site via birds, small mammals, feral hogs, and livestock. Therefore, over time and without treatment, the site will shift toward more dense stands of brush containing both an overstory and a midstory. The main driver to maintain this community is livestock grazing; particularly with sheep and goats having a preference for small shrubs to keep the understory open. Fire can be used as well but the use of fire with a cool season understory is limited. Wildlife browsers generally do not exert sufficient browsing pressure to maintain a savannah on this particular site. If livestock are removed or if grazed only with cattle, a change to the Shrubland/Tree State (3) may occur within 10 to 20 years unless remedial action is taken. Deferment alone will not accomplish any restoration and may well increase the rate of shrub understory establishment.

State 3
Shrubland/Tree State

This state is characterized by the dominance woody plants, reduced herbaceous understory, and absence of warm-season species. Hydrologic cycling, nutrient cycling, and energy transfer are being controlled by juniper and woody canopy.

Community 3.1
Woodland/Shortgrass Community

Figure 26. Clay Loam ecological site. Bexar County

Figure 27. Clay Loam ecological site. Bexar County

Figure 28. Clay Loam ecological site. Bexar County

Figure 29. Clay Loam ecological site. Bexar County

This Woodland/Shortgrass Community (3.1) represents the crossing of a threshold and is a very stable plant community having greater than 25 percent woody canopy dominated by mesquite, oak, and/or juniper with a midstory of shrubs. These shrubs may include algerita (Mahonia trilobata), ephedra (Ephedra spp.), tasijillo (Cylindropuntia leptocaulis), prickly pear (Opuntia spp.), and a diversity of others. This plant community formed when livestock grazing and fire have been removed for a long time; especially when sheep and goats are removed. (This plant community can actually develop from any of the other plant communities given enough time when all management activities cease.) Other species present are elm, hackberry, and live oak. The herbaceous understory is almost non-existent. Shade tolerant species such as Texas wintergrass and cedar sedge are the main herbaceous plants. When the canopy of juniper increases toward a cedar break type community most warm-season grasses have disappeared. Full restoration back to the Reference Plant Community is doubtful and requires the significant intervention of many tools over time to even recover to a resemblance of the Reference Community. The overstory entraps as much as 25 percent of the rainfall (Thurow, 1997) which then evaporates without entering the soil. Most energy is absorbed by the woody plants with some being absorbed by the cool-season herbaceous understory. The soil is covered and exhibits little erosion except for some movement as water flows under the understory. In this case terracettes and litter dams will be observed. Fire is a very limited option for this community so mechanical/chemical tools are needed. Depending upon the past management, it is doubtful that many reference plant community seeds exist for recovery, so seeding may be needed. Because of the overstory canopy, the amount of grass cover is greatly reduced which in turn reduces forage/fine fuel production. Seeding can be used in conjunction with mechanical management.

State 4
Converted Land State

This state is characterized by extensive soil disturbance, followed by reseeding with native or exotic species or a combination. Species diversity and site resilience has been reduced. Depending on previous land use soil structure may be deteriorated, many soil organisms are missing and the site is at-risk of soil erosion.

Community 4.1
Converted Land Community

Figure 32. Clay Loam ecological site. Bexar County

This community is usually the result of mechanical brush control and range planting using a mixture of native grass species. An introduced species may be a part of the seed mixture, some of which can be invasive. Some invasive species are very abundant in the region and can be introduced by equipment, free roaming animals, hay, and means other than range planting. It should be understood however that in some cases introduced grasses can serve part of the same functionality in terms of soil protection and hydrologic characteristic as do natives. Some introduced species, such as kleingrass are not as prone to dominance as are the introduced bluestems. Once invasive grasses have established dominance, restoration to the reference plant community is impractical. If there has been past tillage, the soil heath has deteriorated and the native seed source lost. It will take a long time (if ever) for this state to again reach the reference state. Recovery will involve the use of knock-down herbicides over time as well as replanting of native seeds but even then once they are there, many of the introduced bluestems are persistent. If there is tillage along with crop production and abandonment, this plant community will shift to the 4.2 Abandoned Land Community.

Community 4.2
Abandoned Land Community

Figure 35. Clay Loam ecological site. Bexar County

Figure 36. . Clay Loam ecological site. Bexar County

Figure 37. . Clay Loam ecological site. Bexar County

Extensive conversion of the Clay Loam ecological site to cropland (primarily cotton and corn) occurred from the mid-1800s to the early 1900s. Some remains in cropland today. While restoration of this site to a semblance of the tallgrass prairie is possible with range planting, prescribed grazing, and prescribed burning—complete restoration of the historic community in a reasonable time is very unlikely because of deterioration of the soil structure and organisms. If managerial objectives are exotic grasses, these usually consist of Introduced bluestems (Bothriochloa spp.), kleingrass (Panicum coloratum), and bermudagrass (Cynodon dactylon). The production of these species is highly variable depending upon grazing management, soil health, fertility program, and undesirable plant management. More detailed information is available in Forage Suitability Groups for exotic plants. If abandon land is not seeded and left to natural recovery, it will be doubtful the land will ever recover to any semblance of the reference plant community. Much of the soil health has been degraded and unless remedial efforts to restore the living portions of the soil, the organic matter and the humus, restoration will be difficult. Depending upon the cropping history and the length of cropping, very few remnant seeds persist. Once abandoned, early successional plants that are annuals and weak perennials establish. Over time and with the introduction of some seeds from adjacent areas, higher successional plants establish. However, the plant succession, without intervention with range plantings will probability terminate in a mesquite/baccharis/juniper woody component with prickly pear and small shrubs, and Texas wintergrass as the majority of the plant component. This will be the stable community over time. This community does stabilize the soil and provide the basic building blocks of nutrients, organic matter, and soil organisms needed to restore health. This process is estimated to take over 50 years to manifest. To accelerate the recovery, range planting along with maintenance brush management, prescribed grazing, and possibly fire are needed to restore the ecological process to heal the land.

Pathway 4.1A
Community 4.1 to 4.2

Converted Land Community

Abandoned Land Community

Tillage and farming for crops followed by abandonment triggers this shift.

Pathway 4.2A
Community 4.2 to 4.1

Abandoned Land Community

Converted Land Community

Range planting, maintenance brush management, prescribed grazing, and possibly fire are needed to restore the ecological processes.

State 5
Mulched State

Community 5.1
Hydromulched State

Figure 40. . Clay Loam ecological site. Bexar County

Figure 41. . Clay Loam ecological site. Bexar County

This plant community is a result of using mechanical hydro-mulching to reduce canopy and structure of dense woody species which is usually juniper. The objective of this treatment is to facilitate movement of foot soldiers and to provide protective ground cover. The amounts of mulch on the ground and the orientation of the mulch are dependent upon the amount of woody cover treated and the time since treatment. The mulch tends to settle over time and is very resistant to deterioration. This community can structurally appear very similar to the reference plant community but without the herbaceous cover. The understanding of how this plant community reacts over time is unknown but studies are currently under way to monitor. One result is that the soil is protected for a long time. There will be a need for maintenance to treat juniper and other species as they re-establish.

Transition T1A
State 1 to 2

Continuous season long grazing at moderate to heavy stocking with mixed classes of livestock rate suppress tall grasses. Removal of fire and the lack of brush management as well as adverse weather contribute to the change in the 1.1 plant community to the 1.2.

Transition T1B
State 1 to 3

A lack of fire, integrated brush management and abusive grazing with cattle over long periods of time (30+ years). Alterations of hydrologic cycle, mineral cycle and nutrient cycle are contributing factors. Complete destocking for several years will also lead to a similar situation.

Transition T1C
State 1 to 4

Land clearing, brush management and tillage are the primary drivers to convert land.

Restoration pathway R2A
State 2 to 1

Prescribed grazing coupled with brush management and possibly range planting to restore the ecological process of energy flow and hydrology are needed. Fire should be used strategically in the recovery process. Prescribed grazing with mixed classes of livestock coupled with fire and brush management will help manage resprouts.

Transition T2A
State 2 to 3

Removal of mixed classes of herbivory, a lack of fire and brush management along with the increase of woody plants drive this transition.

Transition T2B
State 2 to 4

Land clearing, brush management and tillage are the primary drivers to convert land.

Restoration pathway R2B
State 3 to 1

Combinations of mechanical treatment, chemical treatments, and many times range planting will be needed to restore this plant community. Prescribed grazing will also be needed. Unless fire is used, prescribed grazing with mixed livestock and brush management will be needed over time.

Transition T3B
State 3 to 4

Land clearing, brush management and tillage are the primary drivers to convert land.

Transition T3A
State 3 to 5

Mechanical hydro mulching is used to reduce canopy and understory.