Ecological dynamics

The reference plant community for this site is tallgrass and midgrass communities along with a good forb component and a few shrubs. The vegetation on the slopes is little bluestem (Schizachyrium scoparium) dominant with some smaller amounts of Indiangrass (Sorghastrum nutans), sand bluestem (Andropogon gerardii) and sideoats grama (Bouteloua curtipendula). The vegetation on the convex ridgetops is sideoats grama, blue grama (Bouteloua gracilis), and a smaller amount of little bluestem. The draws and canyon bottoms are similar to the slopes but generally have slightly more Indiangrass present. The warm-season grasses are C-4 metabolism plants, while the cool-season grasses have C-3 metabolism.

Soil and slope affect vegetation more than other factors. The soil on the ridgetops tends to be deeper and less erosion has occurred over time. There is usually less calcium carbonate present in the surface layer than in the same soil series on the slopes. The more calcium carbonate present, the more little bluestem usually found. The high gyp content of the soils also favors little bluestem. The ridgetops have always been subject to more grazing pressure, even when bison were the primary grazers. Even on the best managed ranches, this distinction in plant communities can be seen.

Fire has played a major role in the development of the plains grassland region. The taller grass species, especially sand bluestem (Andropogon hallii), Indiangrass, and little bluestem respond very positively to occasional fire. The midgrasses and shortgrasses are more fire neutral in response. Shrubs were damaged by fire and thereby are kept in check. It is difficult for shrubs to compete with thick stands of tallgrasses and the fuel loads for fire were such that fires were more damaging to woody plants in pre-settlement times. Most grassland ecologists speculate that fires occurred perhaps every 7 to 12 years on the average. Fire frequency varied of course with the random way fires occurred. Tallgrasses benefited by having old growth removed that had built up in good rainfall years. Old plants that were becoming moribund were replaced by younger plants and the nutrient cycling process was enhanced. Diversity was increased as the fire stimulated forb growth. Wildlife came to the burned areas and grazed the fresh vegetative growth. Shrubs resprouted and offered higher quality browse. Fire helped to maintain plant community balance in keeping with the sites capabilities.

Climatic fluctuations affect annual vegetative production from year to year. Generally speaking, plant communities developed in this fluctuating set of conditions and have adapted to them. The possible exception is that of serious long term drought which occur at times, perhaps only two or three times in a century. Long-term drought (those lasting greater than 5 years) along with abusive grazing may effect plant community balance to such a degree that the former vegetative state may not be quick to be restored.

Grazing distribution is difficult to achieve on this site. The topography limits accessibility and the slopes and dissecting draws affect livestock movement. The ridgetops receive a greater share of grazing pressure. This is true today and was likely true when bison were the principal grazers. The slopes are often in better condition ecologically due to more limited grazing pressure. Abusive grazing is first noticed on the ridgetops and draw bottoms. With abusive grazing, the tallgrasses decrease and sideoats grama and blue grama increase in community makeup. Reference community forbs also decline and woody shrubs begin to become more numerous. Sand sagebrush (Artemisia filifolia) and mesquite (Prosopis glandulosa) both tend to increase with heavy grazing. Mesquite tends to occur more on the ridgetops and sage on the slopes. If the grazing abuse is long-term, then grasses like sand dropseed (Sporobolus cryptandrus), perennial threeawn (Aristida spp.), and buffalograss (Bouteloua dactyloides) will become more and more prevalent and the sideoats grama will decrease to only a token amount. With further abuse, western ragweed (Ambrosia psilostachya) and various annual forbs will become prolific. The blue grama will remain but will become sod bound and very low producing. Once in this degraded state, it is doubtful that a community similar to the reference would be possible to restore, and certainly not with management alone.

The hydrologic function of the site is critically dependent upon the tall and midgrass cover that typifies the reference community. This site yields a good deal of runoff even with good vegetative cover. If cover is poor, then runoff is greatly increased and water erosion is visible. This can create a serious problem with sedimentation downstream. Plant community integrity must be maintained if nutrient cycling is to carry on at maximum levels. This site is a prime example of how productive and functional a site can be with a good plant community and how unproductive and dysfunctional it can be with a degraded community.

The animal community that uses the site for habitat is diverse. In reference condition, this site is ideal habitat for the lesser prairie chicken. There are still a few places where this species can be found on this site. White-tailed deer do use the site but the shrub and tree cover is not sufficient for that specie’s habitat needs. Mule deer utilize the site, and where some shrub cover does occur, bob-white quail will be found. Coyotes, bobcats, jackrabbits, small mammals, and occasional pronghorn will be seen. It is basically a grassland community so most wildlife species are those which inhabit a grassland ecosystem.

Plant Communities and Transitional Pathways:

Narrative:
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 in the diagram. Those shown are some of the most common states observed. This information is intended to illustrate the changes that can occur in certain 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. Changes may occur slowly or fairly rapidly depending on the type of events occurring. At some point in time thresholds are crossed. This means that once changes in vegetation have progressed to some certain point, the balance of the community has been altered to the extent that a return to the former vegetative state is generally not possible, that is, not possible without some form of energy being 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 more easily restored. Usually, changes in management practices alone, such as different grazing methods, will not result in major changes to the community. An example of energy input that might be required to effect change might be the implementation of chemical brush management and complete growing season rest to reduce domination of woody shrubs and change the community to one or more perennial grasses and forbs. This action might have to be done more than once and might take several years. Such a vegetative shift could surely not be accomplished by regulation of grazing alone. The amount of energy required to effect change would depend on the present vegetative state and the desired state.