Upper Columbia Basin Network aspen monitoring report 2007–2017: City of Rocks National Reserve and Craters of the Moon National Monument and Preserve

Strand, Eva; Bunting, Stephen; Johnson, Timothy; Lonneker, Jeff; Dicus, Gordon

doi:10.36967/2298956

The mission of the National Park Service is “to conserve unimpaired the natural and cultural resources and values of the national park system for the enjoyment of this and future generations” (NPS 1999). To uphold this goal, the Director of the NPS approved the Natural Resource Challenge to encourage national parks to focus on the preservation of the nation’s natural heritage through science, natural resource inventories, and expanded resource monitoring (NPS 1999). Through the Challenge, 270 parks in the national park system were organized into 32 inventory and monitoring networks. Quaking aspen was selected as a priority vital sign for the Upper Columbia Basin Network (UCBN), specifically within two UCBN parks—City of Rocks National Reserve (CIRO) and Craters of the Moon National Monument and Preserve (CRMO). Aspen is a focal resource at CIRO and CRMO because of its biological and aesthetic significance. Although aspen comprise only a small percentage of the land cover in the parks, the community type contributes significantly to species diversity and richness. Current observations of aspen decline and die-off in the western states are of concern to natural resource managers and scientists. The sampling design for aspen is divided into three sampling panels. Panel 1 consists of aspen stands in CRMO while panel 2 and 3 consist of aspen stands in CIRO. In 2007, 2010, and 2015, 102 plots in 21 stands were sampled in CRMO. Panel 2, consisting of 85 plots in 15 stands in CIRO, was sampled in 2008, 2011, and 2016, and panel 3 consisting of 49 plots in 10 stands in CIRO was sampled in 2009, 2012, and 2017. This report details status estimates for aspen and conifer densities by size class in CIRO and CRMO and a statistical trend analysis for stands sampled 2007–2017. Park average stem densities (stems per hectare) for aspen and conifer species are summarized in Table ES-1. The aspen protocol (Strand et al. 2009b) was approved in September 2009. The methods presented in this report reflect that version, version 1.0 of the protocol. The majority of the aspen stands sampled in CRMO and CIRO 2015–2017 are regenerating and contain a distribution of age classes. There are however stands with relatively low mature aspen stem density, low regeneration, and/or high numbers of dead aspen stems. Regeneration lower than 1000 stems/ha was recorded in three stands in CRMO in 2015: stand #5, stand #26, and stand #27. Mature stem density lower than 100 stems/ha was recorded in four stands in CRMO in 2015: stand #5, stand #12, stand #13 (0 stems/ha), and stand #20 (0 stems/ha). Regeneration lower than 1000 stems/ha was recorded in CIRO in two stands in 2016–2017: stand #24 and stand #51. The stand with the lowest mature stem count in CIRO was stand #72 (149 stems/ha). Even though a few stands in both parks had a low to no density of mature stems, they were still suckering and recruitment of young stems was occurring. The number of stands in CRMO with conifers in the regeneration class increased from one stand in 2007 to ten stands in 2015, ranging from 25 to 199 stems/ha in 2015. The number of stands with conifers in the seedling class in CRMO increased from seven in 2007 to eleven in 2015, ranging from 25 to 398 stems/ha in 2015. Density of mature conifers was low in CRMO and decreased from 14 to 6 stems/ha between 2007 and 2015. In CIRO, the number of stands with conifers in the regeneration class stayed constant at 13–14 stands (33–398 stems/ha) while in the seedling class we observed an increase from nine in 2008/2009 to twelve in 2016/2017 ranging from 50 to 497 stems/ha in 2016/2017. The number of stands with mature conifers increased from eight to twelve in CIRO from 2008/2009 to 2016/2017, ranging from 33 to 597 stems/ha in 2016/2017. Data from 2007 to 2017 were tested for a change in stem density in aspen and conifers within size groups between sampling periods using a linear mixed model analysis. Significant increases (p<0.05) were detected for the aspen regeneration class in CRMO from 2007 to 2010 and from 2007 to 2015. A significant decrease in dead aspen stems was detected between 2007 and 2015 in CRMO. There were no statistically significant differences in aspen sucker density or mature stem density in CRMO although mature aspen density decreased by 16.5% from 2007 to 2015. An increase in aspen suckering was observed in panel 2 between 2008 and 2011 and in panel 3 between 2009 and 2012 in CIRO, but no change was detected in CIRO’s panels between 2008 and 2016 or 2009 and 2017. Increases in the aspen regeneration class was observed in CIRO in panel 2, 2008 to 2011 and 2008 to 2016, while a decrease in aspen regeneration was observed in panel 3 2009 to 2017. Significant increases in stem density of the mature class was observed in CIRO in both panels across all time periods. An increase in dead aspen stems occurred between 2008 and 2011 but there was no difference between 2008 and 2016 or in panel 3. General observations suggest that stands on warmer aspects (south and west), lower elevation, and higher on the hillslope have lower aspen regeneration density. An increase in the conifer regeneration class was detected in CRMO while a decrease was detected in panel 2 in CIRO 2008 to 2016. An increase in conifer seedlings was detected in panel 3 in CIRO 2009–2017.

Upper Columbia Basin Network aspen monitoring report 2007–2017: City of Rocks National Reserve and Craters of the Moon National Monument and Preserve

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