Camas monitoring in Nez Perce National Historical Park’s Weippe Prairie: 2012 annual report

Rodhouse, Thomas; Stucki, Devin

This annual report details findings from 2012, and puts these findings within the context of the entire 8-year monitoring program. Trend analysis for the Weippe Prairie camas population over the period 2005-2010 was provided by Rodhouse et al. (2011), reporting an overall estimate of 9% per year increase, on average, in the median number of established camas plants/ m2, excluding seedlings, but with a relatively wide 95% credible interval (CRI) of 0-19%, reflecting the variation in observed trend among the 5 management zones of the prairie. The NPS acquired the Weippe Prairie site in 2003, after many years in which the site was intensively grazed and mowed for livestock hay. Interpretation of this positive trend is that the effect of the NPS management, de facto “passive restoration”, has benefitted the wetland ecosystem of the site and facilitated a rebounding camas population. Based on the 2012 survey, this increasing trend in camas density appears to be abating somewhat. Density counts were lower in 2012 compared with recent years in all zones. Wet spring weather in 2011 and prolonged inundation of parts of the prairie through late spring (Rodhouse and Stucki 2013) may have contributed to this synchronous drop in density counts across the site. Conversely, the warmer temperatures and average precipitation in April 2012 might have suppressed germination and flowering. The patterns of weed frequency in quadrats for two species targeted by park management for control and eradication, orange hawkweed (Hieracium auranticum) and sulphur cinquefoil (Potentilla recta), continue to be highly variable among zones, and over time. It is important to note that the patterns of trend reported here are potentially confounded by spatial variation in microtopography, and, more generally, spatial autocorrelation. Rodhouse et al. (2011) demonstrated the importance of accounting for spatial variation in the first formal model-based trend analysis. A second formal trend analysis will be conducted after the 10th year of monitoring in 2014. A 10-year time series will allow for the influences of winter and spring precipitation to be investigated as well. Therefore, the trends reported here should be considered preliminary and contingent on subsequent modeling.

Camas monitoring in Nez Perce National Historical Park’s Weippe Prairie: 2012 annual report

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