Ecological dynamics

The Reference Plant Community consists of mid and shortgrasses with few tallgrasses. Some perennial forbs are present with small numbers of annual forbs and a few scattered woody shrubs. Productivity is moderate with most of the production coming from sideoats grama (Bouteloua curtipendula) and blue grama (Bouteloua gracilis). Lesser amounts of buffalograss (Bouteloua dactyloides), hairy grama (Bouteloua hirsuta), sand dropseed (Sporobolus cryptandrus), and perennial three-awn (Aristida wrightii) are found on the site. Vine mesquite (Panicum obtusum) and western wheatgrass (Pascopyrum smithii) are found growing in depressional areas. Small pockets of sand bluestem (Andropogon hallii) and Indiangrass (Sorghastrum nutans) may be found scattered throughout the site. Little bluestem (Schizachyrium scoparium) will occur in small amounts where the soil becomes shallower. The more commonly found forbs are dotted gayfeather (Liatris punctata), scarlet globemallow (Sphaeralcea coccinea), Engelmann’s daisy (Engelmannia peristenia), baby white aster (Chaetopappa ericoides), halfshrub sundrop (Calyophus serrulatus), trailing ratany (Krameria lanceolata) and annual forbs. The primary woody species found are yucca (Yucca glauca) and broom snakeweed (Gutierrezia sarothrae), with an occasional catclaw mimosa (Mimosa aculeaticarpa var. biuncifera) and plains pricklypear (Opuntia polycantha); however, trees are seldom found on this site.

The site occurs on slightly to moderately sloping areas on upland plains where some small amount of geologic erosion may have occurred and the soils are somewhat “thinner” than those of the associated Deep Hardland ecological site that occurs on the more level terrain. Higher calcium carbonate content throughout the soil profile accounts for the amount of sideoats grama growing on this site. This differs from the closely associated Deep Hardland site that is dominated by blue grama. The forb component is more apparent in years of above average rainfall. Pronghorn favor this site because of the variety of forbs present. Cryptogamic crusts are more common on this site than on nearby Deep Hardland sites. Production on this site is quite close to that of the Deep Hardland sites. The two main indicator plants on the Limy Upland ecological site are sideoats grama and yucca. Yucca has a tendency to increase on limy upland sites that have had regular spring and early summer deferment for many years with good yucca seed production. Yucca blooms are very palatable to deer, pronghorn and cattle.

Fire played a role in the ecology of this site as well as all other high plains sites. The general role of fire was to sustain natural grassland and suppress shrubby species. Fire helped to keep a balance between the grasses, forbs and shrubs. However, in the shortgrass region, fire was probably secondary to climate in promoting the historic vegetative state. A drier climate (50 percent). Typical herbaceous vegetation will be perennial three-awn, low quality shortgrasses, and low vigor, sod bound blue grama. The large, connected bare areas will have numerous annual species present. The loss of herbaceous cover and increased bare ground encourages accelerated erosion. Nutrient cycling, the water cycle, watershed protection and biological functions are not functioning well in this phase. Restoration of the Shortgrass/Annuals Community (3.1) to reference conditions will require major energy, economic and management inputs. Conservation practices required include prescribed grazing with several consecutive (3-4 years) rest periods during the growing season, re-seeding bare areas with adapted native grass species, and chemical brush and pest management. Prescribed burning is not an option in this phase. Full recovery and maintenance of the reference community requires continued proper grazing management as well as occasional brush and pest management.

NOTE: Rangeland Health Reference Worksheets have been posted for this site on the Texas NRCS website (www.tx.nrcs.usda.gov) in Section II of the eFOTG under (F) Ecological Site Descriptions.

STATE AND TRANSITIONAL PATHWAYS: (DIAGRAM)
The following diagram suggests some pathways that the vegetation on this site might take in response to various treatment or natural stimuli over time. There may be other states not shown on the diagram. Those shown are some of the most commonly seen. This information is intended to illustrate the changes in vegetative states that can occur in a given set of circumstances, and may not happen this way in all cases. Local professional guidance should be sought when making plans to manipulate plant communities for specific purposes.

As a site changes in the structure and makeup of the plant community, the changes may be due to management or due to natural occurrences or both. At some point in time thresholds are crossed. Once changes have progressed to a certain point, the balance of the community has been altered to the extent that a return to the former state is generally not possible. Some form of energy must be applied in order to make the community respond in that direction. These changes in plant communities occur on all ecological sites with some sites being more resistant to change than others. Also, some sites seem to be more resilient being able to heal or restore more easily than other sites. Usually, changes in management practices alone, such as different grazing methods, will not result in restoration of former vegetative states. An example of an energy input that might be necessary to effect change might be the implementation of chemical brush management and complete growing season rest to reduce domination of woody shrubs and promote more perennial grasses and forbs. This might have to be done more than once and could take several years. Such a vegetative shift could not be accomplished by regulation of grazing alone. The amount of energy required to effect a change would depend on the present vegetative state and the desired state.