Survey of plant communities of kipukas within Craters of the Moon National Monument and Preserve

Huntly, Nancy

We visited and sampled kipukas at Craters of the Moon National Monument and Preserve (CRMO) during 2004 and 2005, focusing in particular on their plant communities, but also recording other attributes, including cultural and natural resources. Some putative kipukas proved either to be misclassified from aerial images or were false kipukas (apparently areas of lower lying lava over which some soil had drifted), and we updated the CRMO GIS kipuka database to reflect this. For the true kipukas, we sampled the plant community by visual survey, by using a point-frame to estimate percent cover of each species present, or both. We also recorded kipuka attributes and evidence of cultural and natural resources, using a checklist (Resource Observation Form) that was developed by CRMO personnel. We sampled 88 distinct kipukas during the 2-year survey using one or both methods. Additionally, percent cover of all species was sampled for a set of 12 randomly selected kipukas both in both years to provide a baseline of annual variation and longer term trends in abundances of plant species. We identified 174 total species from the 88 kipukas that were surveyed in 2004 and 2005. This species list is not exhaustive, as some plants could not be identified because they did not have diagnostic characters at the time a kipuka was visited. A list of species identified in this survey is included as Appendix A, and lists of species recorded from each sampled kipuka are included as Appendix B. No state-listed noxious species were found on any of the surveyed kipukas, but 17 non-native species were recorded. The invasive annual grass, Bromus tectorum (cheatgrass) was the most abundant and widespread of the non-natives and was on most of the kipukas that were surveyed, excepting those of the North region of CRMO, where it was neither common nor abundant. B. tectorum was present on 84% of the sampled kipukas, was present on 78% of the kipukas that were sampled by point-frame in 2005, and was often the most abundant or one of the most abundant species on a kipuka. Additionally, there were fewer total species of plants on kipukas where B. tectorum was more abundant. The most abundant and frequent of the non-native forbs were Sisymbrium altissimum (tall tumblemustard), Draba verna (spring whitlow grass), Lactuca serriola (prickly lettuce), Tragopogon dubius (dandelion), and Alyssum desertorum (desert madwort). Because kipukas are insular patches of sagebrush steppe vegetation surrounded by lava, one might expect that measures of insularity, particularly kipuka size and isolation, would predict the diversity of plant species present in the flora of a kipuka. We examined this possibility, but found that neither area nor isolation was a strong predictor of plant species diversity. Larger kipukas had a weak tendency to have more species, but some small kipukas had as many plant species as the larger kipukas. Isolation explained somewhat more of the variation in plant diversity of kipukas, but the relationship was not as expected. Kipukas that were more distant from the edge of the lava flows, so more isolated from the surrounding historic sagebrush steppe landscape, had more plant species, contrary to the expectation that habitat isolation results in lower diversity. 1 Another measure of isolation, distance to the nearest other kipuka, explained somewhat more of the variation in plant diversity of kipukas. Kipukas that were nearer other kipukas had higher numbers of plant species than kipukas that were farther from other kipuka. Collectively, these results suggest that isolation from the landscape surrounding the lava flows of CRMO has helped preserve the diversity of the sagebrush steppe flora of the kipukas, perhaps by protecting kipukas from intensive use by people, reducing the likelihood of fire, or reducing likelihood of establishment of ...

Survey of plant communities of kipukas within Craters of the Moon National Monument and Preserve

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