Risk Associated with Rangeland Health and Sustainability
Risk Management for Texans Series
RLEM No. 5 August 2000
Allan McGinty
Professor and Extension Range Specialist
Texas AgriLife Extension Service
San Angelo, Texas
Introduction
Texas rangelands are a multiple use natural resource. From rangelands meat and fiber are produced, most of the wildlife in the state are found, and the majority of the water used by our cities, agriculture and industry is captured for storage in lakes or underground aquifers. Also, rangelands provide recreational opportunities such as hiking, off road recreational vehicle use, birding, camping, etc. as well as providing aesthetic beauty to the landscape. The health and sustainability of Texas rangelands are important to every citizen of this state.
What is Healthy Rangeland?
Healthy rangelands as compared to unhealthy rangelands usually have a greater diversity of plant and animal species. Plant communities are dominated by perennial plants as compared to annuals. Healthy rangelands have minimum erosion, because the soil surface has sufficient plant cover to protect it from the impact of raindrops. This plant cover also serves to slow the movement of water across the soil surface, resulting in greater water infiltration rates as compared to unhealthy rangelands. Healthy rangelands produce a greater and more dependable quantity of herbaceous forage for use by livestock and wildlife. And most importantly, healthy rangelands ecological processes, including the hydrologic cycle, nutrient cycle and energy flow are all functioning, supporting healthy biotic populations and communities.
What are the Risks of Unhealthy Rangelands?
Unhealthy rangelands have accelerated loss of soil through excessive water or wind erosion. This soil loss increases sedimentation of streams, rivers and above ground aquifers, reducing their storage capacity and life. Unhealthy rangelands also have reduced recharge of underground aquifers due to lower infiltration rates. Soil loss from accelerated erosion reduces the volume of soil available for storage of water and thus the production potential for livestock and wildlife. Unhealthy rangelands have less diverse populations of animals and plants which reduces the ecosystems resilience to adverse conditions. Unhealthy rangelands generally produce less forage for livestock. Unhealthy rangeland have reduced habitat value, essential as cover and food for wildlife. Unhealthy rangelands function poorly or are have completely dysfunctional basic ecological processes required to sustain the ecosystem over time. In many cases, mis-management resulting in unhealthy rangelands is irreversible.
What are Some Warning Signs of Unhealthy Rangeland?
Pedicelled plants: Grass plants, each setting on a small pedicel of soil, is a warning sign of sheet erosion on the site. The plant root system and crown protects the soil directly underneath, but soil between plants is lost downslope with each rainfall event. Soil depth is important for the storage of water for plant growth between rainfall events. It is possible, with unprotected soil to loose over an inch of topsoil during a single rainstorm event, which in turn may take centuries to replace through natural processes.
Bare Ground: Large areas or increasing areas of bare ground are a symptom of unhealthy rangeland. The soil must be covered with vegetation or mulch to protect the soil surface from the impact of raindrops. Unprotected soil becomes dislodged during rainfall events, and moves downslope into gullies, streams and rivers. Unprotected soil is susceptible to forming crusts, due to a loss of structure and organic matter at the soil surface, which reduces water infiltration, recharge of underground aquifers and the quantity of water stored in the soil profile for plant growth.
Browse Lines: A distinct absence of woody plant vegetation from ground-line to a height that browsers like goats and deer can reach, is an indication of excessive use of this component of the plant community. Too heavy use of any part of a plant community will result in reduced plant diversity and lower overall range health. The strength of rangeland ecosystems is their diversity, in both animals and plants. Diversity protects both the health and sustainability of the system over time.
Gullies and Steep Denuded Stream Banks: Gullies and steep stream banks devoid of vegetation are another sign of excessive erosion and poor rangeland health. Vegetation on stream banks hold soil and slow water movement during high stream-flow events, while dissipating stream-flow energy. Treatment to counteract the formation of gullies and steep stream banks should not only include slowing water movement through these areas, but also careful examination and correction of the factors that led to their development in the first place.
Plant Communities Dominated By Annual Plants: Unfortunately, if rangelands are abused through over-use, the plant communities will change from perennial species to annual species. Annual species have life cycles that permit them to take advantage of short-term, favorable growing conditions. Unfortunately they do not provide the soil surface with dependable, continuous protection from raindrop impact, or provide dependable forage for livestock and wildlife.
How Do I Monitor for these Warning Signs?
Monitoring rangelands are important because it improves the owner/managers ability to make proper and timely decisions. Rangelands are very complex. Any given pasture may be composed of several different range sites, each with different plant communities. Each plant community has its own mix of grass, forb and woody plant species. This mix of species changes over time due to the impact of weather, seasons, brush and weed management, and grazing pressure by livestock and wildlife. Any monitoring system should key on changes in this plant community and any observable symptoms of accelerated erosion. The owner/manager must monitor these changes to insure 1)management is not causing damage to soil, water quality and the rangeland resource base, and 2) that past decisions are producing expected results.
Rangelands can be monitored using a variety of methods. Some of the more common techniques include vegetation sampling, excluding small areas from grazing or photo points. The latter method is one of the easiest to use by most individuals. By comparing photographs and detailed notes for the exact same location over time, change and current rangeland health can be observed and documented. The photographs, notes and interpretations serve as a permanent record for each location and situation. These observations and photographic record are necessary to establish the cause for changes in resource conditions. Photo points provide a means of monitoring rangeland health with a minimum of input in terms of time and expense.
When comparing photographs for a specific photo point over time, look for changes in the amount of forage, brush, weeds, bare ground, litter and evidence of erosion; for changes in the types of plants found in the photographs (plot); and for the absence or presence of specific plants. Records, i.e. grazing use, brush management and rainfall will be invaluable in interpreting these photographs. For detailed information on how to set up and interpret photo points to monitor range health obtain publication L-5216 “Range Monitoring with Photo Points” from the local county Extension agent or through the Internet (http://texaserc.tamu.edu/catalog/topics/Rangelands.html).