Variance and power for trend assessment of pilot data, integrated upland monitoring, Canyonlands National Park
Witwicki, D. 2010. Variance and power for trend assessment of pilot data, integrated upland monitoring, Canyonlands National Park. Natural Resource Report. NPS/NCPN/NRR—2010/171. Natural Resource Program Center. Fort Collins, Colorado
This report describes the power analysis conducted by the Northern Colorado Plateau Network to identify an “affordable” sample size that optimizes tradeoffs between trend and status estimation and overall operational reality for its integrated uplands monitoring protocol at Canyonlands National Park. Power analysis provides an a priori understanding of our ability and confidence to estimate the condition (i.e., status) of a resource and detect trends in that resource over time. This report describes the power analysis conducted by the Northern Colorado Plateau Network to identify an “affordable” sample size that optimizes tradeoffs between trend and status estimation and overall operational reality for its integrated uplands monitoring protocol at Canyonlands National Park (NP). Forty plots were monitored at Canyonlands NP for three consecutive years. Key response measurements for (1) understanding the susceptibility of soil to wind and water erosion and (2) detecting shifts in vegetation were used in this analysis. For each key response, we estimated the variance separately for shrub and grassland ecological site types, using linear mixed-effects models. We also examined power and precision of standard error of status for alternative revisit designs and sample sizes, as well as for the ability to detect different amounts of annual trend. The operational survey and revisit designs for Canyonlands NP are presented in the report. Graphs of power for trend are presented in Appendix A.
- Type
- Published Report
- Authors
- Witwicki,, Dana
- Date of Issue
- 2010-01
- Publisher
- Natural Resource Program Center
- Units
- CANY , NCPN , NRSS
- Keywords
- Colorado Plateau, Grasslands, Monitoring, NCPN Uplands Monitoring, Plant Studies, power analysis, revisit design, Shrublands, Upland, Uplands