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general_design_topics:when_key_areas_aren_t_anymore [2010/05/17 19:15] jasonkarl |
general_design_topics:when_key_areas_aren_t_anymore [2010/05/17 20:03] (current) jasonkarl |
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| Key areas are selected based on management objectives with an understanding of how different management and natural processes interact to impact the environment (i.e, create patterns on the ground) (BLM 1996). Key areas should be placed within a single ecological site or plant community (i.e., not in transition zones or ecotones), and in areas that are likely to show a response to management actions. The number of key areas needed depends on the size and variability of the area and the management objective. | Key areas are selected based on management objectives with an understanding of how different management and natural processes interact to impact the environment (i.e, create patterns on the ground) (BLM 1996). Key areas should be placed within a single ecological site or plant community (i.e., not in transition zones or ecotones), and in areas that are likely to show a response to management actions. The number of key areas needed depends on the size and variability of the area and the management objective. | ||
| - | For instance, in arid rangeland in the western U.S., livestock are often limited in their distribution to within a relatively short distance to water (generally less than 2 miles), with the degree of use of land by livestock decreasing as you move away from the water source. Beyond approximately 2 miles, there is little grazing impact because the animals rarely get out there, so there is little need to monitor this area. Areas close to the water source get lots of use, are also not representative of the impact of grazing, and generally are not monitored as key areas (although the condition and trend of these areas may be monitored separately as critical areas). In the simple example illustrated in figure 1, key areas might be located in a doughnut-shaped buffer around the water source (see figure below). | + | For instance, in arid rangeland in the western U.S., livestock are often limited in their distribution to within a relatively short distance to water (generally less than 2 miles), with the degree of use of land by livestock decreasing as you move away from the water source. Beyond approximately 2 miles, there is little grazing impact because the animals rarely get out there, so there is little need to monitor this area. Areas close to the water source get lots of use, are also not representative of the impact of grazing, and generally are not monitored as key areas (although the condition and trend of these areas may be monitored separately as critical areas). In the simple example illustrated in Figure 1, key areas might be located in a doughnut-shaped buffer around the water source (see figure below). |
| {{:general_design_topics:key_area1.png?width=350|}}\\ | {{:general_design_topics:key_area1.png?width=350|}}\\ | ||
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| Considering the grazing example, a stratified random sample may not be as efficient as the key area approach because it involves sampling more locations, but it offers several important advantages: | Considering the grazing example, a stratified random sample may not be as efficient as the key area approach because it involves sampling more locations, but it offers several important advantages: | ||
| - | * Because the sample locations could be located anywhere in the entire area, the stratified random sample preserves the [inference space] as the full extent of the allotment. In other words, conditions measured at the random sample locations can be statistically extended to the larger area of interest. | + | * Because the sample locations could be located anywhere in the entire area, the stratified random sample preserves the [[inference space]] as the full extent of the allotment. In other words, conditions measured at the random sample locations can be statistically extended to the larger area of interest. |
| * As long as the sample locations were selected using a randomized procedure, estimates derived from the random sample locations are statistically unbiased. | * As long as the sample locations were selected using a randomized procedure, estimates derived from the random sample locations are statistically unbiased. | ||
| * Because they were selected at random from all possible locations within the allotment, the random sample locations can be used to address several different assessment and monitoring objectives. In contrast, because the key areas were selected to evaluate the impacts of grazing, they can only be reliably used for that purpose (and only while the conditions under which they were originally selected remain). | * Because they were selected at random from all possible locations within the allotment, the random sample locations can be used to address several different assessment and monitoring objectives. In contrast, because the key areas were selected to evaluate the impacts of grazing, they can only be reliably used for that purpose (and only while the conditions under which they were originally selected remain). | ||
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| {{:general_design_topics:key_area3.png?width=350|}}\\ | {{:general_design_topics:key_area3.png?width=350|}}\\ | ||
| - | <sub>Figure 3. The same system and sample locations as in Figure 2 above, but with the addition of a new natural gas well and improved roads.</sub> | + | <sub>**Figure 3.** The same system and sample locations as in Figure 2 above, but with the addition of a new natural gas well and improved roads.</sub> |
| The gas well and the improved roads both have influence over conditions in a portion of the allotment. These areas may overlap the influence zones of grazing. The random sample locations are capable of recording any changes in condition associated with the new well because they are stratified by ecological site and located in the allotment without regard to any particular management activity. On the other hand, the key areas, because they were placed to monitor grazing management, do not provide a good indication of representative conditions with regard to impacts of the gas well. Additionally, the influences of the gas well and improved roads may affect the key areas and make them no longer very representative of grazing impacts. This kind of effect could lead to determination of adverse grazing effects when in fact, the change was due to some other management activity! | The gas well and the improved roads both have influence over conditions in a portion of the allotment. These areas may overlap the influence zones of grazing. The random sample locations are capable of recording any changes in condition associated with the new well because they are stratified by ecological site and located in the allotment without regard to any particular management activity. On the other hand, the key areas, because they were placed to monitor grazing management, do not provide a good indication of representative conditions with regard to impacts of the gas well. Additionally, the influences of the gas well and improved roads may affect the key areas and make them no longer very representative of grazing impacts. This kind of effect could lead to determination of adverse grazing effects when in fact, the change was due to some other management activity! | ||