Triggers are within-season guides for livestock managers to make changes or move livestock, ensuring that end-point indicators (described below) are met (not to be confused with state and transition model triggers). For instance, animal movements may be triggered by use levels. The University of Idaho Stubble Height Review Team (2004) described proper use of triggers for riparian management. Triggers must be location and management-plan specific. Also, recording use level at the end of grazing, when this occurs within the growing season, is useful even when the move was not triggered by the level of use. See grazing response index in the Ranchers' Monitoring Guide (Perryman et al. 2006; Wyman et al. 2006).
Triggers may be included in grazing management plans after cooperative development by land and livestock managers. Triggers and end-point indicators, along with other required management practices, are expected to achieve long-term desired conditions. When using within-season triggers and end-point indicators, the monitoring strategy must not only measure and evaluate whether or not the allowable numeric value was met, but also whether the value is correct. If measures of annual use indicate that the desired grazing intensity or strategy is too much or too little, or is inconsistent with achieving the desired resource objectives, then the agency and the permittee should implement corrections. This is part of the adaptive management process.
End-point indicators are end-of-season guides for land managers to assess resource use impacts at the end of the grazing and growing season, whichever comes last. Assessment of both triggers and end-point indicators helps to determine if grazing use left resources in an appropriate condition for moving toward objectives. Generally, end-point indicators cannot by themselves determine whether a particular grazing system is contributing to recovery or conversely, contributing to degradation (BLM 1999b). This is especially true of a single year's values (Smith et al. 2005).
Across broad and diverse areas, different values of a given indicator or different indicators would be selected for different vegetation types and objectives. For example, crested wheatgrass, with its resilience to grazing pressure and tendency toward wolf plants (plants that have grown large and accumulated unpalatable thatch through lack of use), might have a higher utilization level than would be suitable for bluebunch wheatgrass, a species more susceptible to defoliation impacts. A pasture might have a higher acceptable target utilization level if grazed in a rotation with a short-use period than for the same area if grazed every year for a longer period, especially if that grazing use coincided with the reproductive phase of plant growth.
Swanson, S., Schultz, B., Novak-Echenique, P., Dyer, K., McCuin, G., Linebaugh, J., Perryman, P., Tueller, P., Jenkins, R., Scherrer, B., Vogel, T., Voth, D., Freese, M., Shane, R., McGowan, K., 2018, Nevada Rangeland Monitoring Handbook (3rd) | Chapter 05 - Triggers and Indicators, Extension | University of Nevada, Reno, SP-18-03
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