Thomas Landzert Block 3 4/27/10 A.P.E.S. Rangeland Study Guide Rangelands: Rangelands are being compromised by overgrazing and desertification. The federal government is trying to mange and sustain the rangelands. 1. Overgrazing: Overgrazing, which was the theme of the essay “The Tragedy of the Commons,” occurs when plants are exposed to grazing for too long without sufficient recovery periods. When a plant is grazed severely, it uses energy stored in its roots to support regrowth. As this energy is used, the roots die back. The degree to which the roots die back depends on the severity of the grazing. Root dieback does add organic matter to the soil, which increases soil porosity, the infiltration rate of water, and the soil’s moisture holding capacity. If sufficient time has passed, enough leaves will regrow and the roots will regrow as well. A plant is considered overgrazed when it is regrazed before the roots recover. Overgrazing can reduce growth by up to 90%. Consequences to overgrazing include pastures becoming less productive, soils having less organic matter and becoming less fertile, and a decrease in soil porosity. The inflation rate and moisture holding capacity of the soil drops and susceptibility to soil compaction increases. Additionally, desirable plants become stressed, while weedier species thrive in harsher conditions. Overgrazing causes biodiversity to decrease by destroying banks and streambeds, thereby increasing silting. Eutrophication increases due to cattle wastes. Therefore, aquatic environments are negatively impacted. Predator prey relationships and the balance achieved through predator control programs are affected. Overgrazing increases the incidence of disease in native plant species. Finally, land is affected to the point where sustainability is threatened. 2. Desertification: Desertification is the conversion of marginal rangeland or cropland to a more desert like land type. It is often caused by 1. Overgrazing 2. Soil Erosion 3. Prolonged drought 4. Or climate changes as well as the overuse of available resources such as nutrients and water. Desertification proceeds with the following steps. 1. Overgrazing results in animals eating all available plant life. 2. Rain washes away the trampled soil, since nothing holds water anymore. Wells, springs, and other sources of water dry up. What vegetation is left dies from drought or is taken for firewood. 3. Then weeds that are unsuitable for grazing maybe begin to take over. The ground becomes unsuitable for seed germination. 4. Finally, wind and dry heat blow away the topsoil.
3. Deforestation: Deforestation is the conversion of forested areas to nonforested areas. They are used as grasslands for livestock grazing, grain fields, mining, petroleum extraction, fuel wood cutting, commercial logging, tree plantations, and urban sprawl. Natural deforestation can be caused by tsunamis, forest fires, volcanic eruptions, glaciations, and desertification. Deforestation results in a degraded environment with reduced biodiversity and reduced ecological services. Deforestation threatens the extinction of species with specialized niches, reduces the available habits for migratory species of birds and butterflies, decreases soil fertility brought about by erosion, and allows runoff into aquatic ecosystems. It also causes changes in local climate patterns and increases the amount of carbon dioxide released into the air from burning and tree decay. In addition to the direct effects brought about by deforestation, indirect effects caused by edge effects and habitat fragmentation can also occur. Methods that are currently employed to mange and harvest trees include: Even age management Essentially the practice of tree plantations Uneven age management Maintain a stand with trees of all ages from seedling to mature Selective cutting Specific trees in an area are chosen and cut High grading Cutting and removing only the largest and best trees Shelterwood cutting Majority of trees are removed except for scattered, seed producing trees used to regenerate a new stand. Clear Cutting All of the trees in an area are cut at the same time. This Technique is sometimes used to cultivate shade intolerant tree species Strip cutting Clear cutting a strip of trees that follows the land contour. The corridor is allowed to regenerate. Deforestation alters the hydrologic cycle, potentially increasing or decreasing the amount of water in the soil and groundwater. This then affects the recharge of aquifers and the moisture in the atmosphere. Shrinking forest covers lessens the landscape’s capacity to intercept, retain, and transport precipitation. Instead of trapping precipitation, which then percolates to groundwater systems, deforested areas become sources of surface water runoff, which moves much faster than subsurface flows. The faster transport of surface water can translate into flash flooding and more extreme floods than would occur with the forest cover. Deforestation also contributes to decreased evaportationspriation. This lessens atmospheric moisture and precipitation levels. It also affects precipitation levels downwind from the deforested area as water is not recycled to downwind forest but, instead, is lost in runoff and returns directly to the oceans. Forests are also important carbon sinks. Forests can extract carbon dioxide and pollutants from the air, thus
contributing to biosphere stability and reducing the greenhouse effect. Forest are also valued for their aesthetic beauty and as a cultural resource and tourist attraction. 4. Federal Rangeland Management Rangelands comprise about 40% of the landmass of the United States and are the dominate type of land in arid and semiarid regions. Nearly 80% of lands of the western United States are classified are rangelands, whereas only 7% of some areas near the East Coast are classified as rangelands. Rangelands provide valuable grazing lands for livestock and wildlife. Rangelands serve as a source of high quality water, clean air and open spaces. They benefit people as a setting for recreation and as an economic means for agriculture, mining, and living communities. Rangelands serve multiple purposes: A habitat for a wide array of game and nongame animal species A habitat for a diverse and wide array of native plants species A source of high quality water, clean air and open spaces A setting for recreational hiking, camping, fishing, hunting, and nature experiences The foundation for low input, fully renewable food production systems for the cattle industry Jurisdiction of public grazing rangelands is coordinated through the Forest Service and the Bureau of Land Management (BLM). Before 1995, grazing policies were determined by rancher advisory boards composed of permit holders. After 1995, resource advisory councils were formed made up of diverse groups representing different viewpoints and interests. 40% of all federal grazing permits are owned by 3% (or approximately 2000) of all livestock operators. Federal grazing permits average about 5 cents per day per animal through federal subsides. The True cost of doing business would make this fee closer to $10 to $20 per animal per day. Methods of rangeland management include: 1) Controlling the number and distribution of livestock so that the carrying capacity is not exceeded 2) Restoring degraded rangeland 3) Moving livestock from one area to another allow the rangeland to recover 4) Fencing off riparian areas to reduce damage to these sensitive areas 5) Suppressing the growth of invasive plant species 6) Replanting barren rangeland with native grass seed to reduce soil erosion 7) Providing supplemental feed at selected sites 8) Locating water holes, water tanks and salt blocks at strategic points that do not degrade the environment Land administered by the BLM is inhabited by 219 endangered species of wildlife. Livestock grazing is the fifth rated threat to endangered plant species, the fourth leading threat for all endangered wildlife, and the number one threat to all endangered species in arid regions of the United States.