Demographic monitoring of Spalding's catchfly (Silene spaldingii S.Watson) in Idaho canyon grasslands, Snake and Salmon Rivers (2004-2013) Final Report

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Spalding’s catchfly (Silene spaldingii S.Watson) is a rare plant endemic to the bunchgrass, sagebrush-steppe, and open pine communities of the inland Pacific Northwest. Large portions of these habitats have been eliminated by cultivation or degraded by livestock grazing and non-native plant invasion. Spalding’s catchfly was listed as Threatened by the U. S. Fish and Wildlife Service (USFWS) in 2001. The USFWS contracted the Idaho Natural Heritage Program (IDNHP, then the Idaho Conservation Data Center) to establish long-term demographic and habitat monitoring plots in the canyon grasslands of the Snake and Salmon Rivers surrounding Craig Mountain, Idaho. Due to some individual plants remaining invisible belowground in a dormant state in any given year, a minimum of 10 consecutive years of demographic monitoring was needed to obtain accurate demographic estimates. The IDNHP established 10 monitoring plots in the Craig Mountain area, eight in the Snake River drainage in 2002 and two in the Salmon River drainage in 2004. In 2002 and 2003, data for the eight Snake River plots were collected once during the growing season at flowering time in late July. The monitoring protocol was modified in 2004 to include both an early season (early June) and a late season (late July/early August) sampling period when it became obvious that demographic data based solely on late season sampling was incomplete and biased. We also collected information on potential threats and habitat characteristics. In July of 2007, the eight Snake River plots burned, providing a rare opportunity to assess the effects of fire on Spalding’s catchfly and its habitat by comparing pre-burn and post-burn data from the same plots. This report summarizes the demographic and habitat data collected on these 10 plots from 2004 through 2013. <br> Over the study period, we identified a total of 795 different, individual plants in all plots. We classified them each year into four life stage classes, three aboveground classes (rosette, single-stem, multi-stem) and one belowground class (dormant). Plants spent 40% of their time in the single-stem class, 35% in the rosette class, 20% in the multi-stem class, and 8% in the dormant class over the study period. Annual recruitment was low, averaging 5% from 2007 to 2010 and then increased markedly, averaging 22% the last three years of the study. Annual dormancy rates were low and varied minimally, averaging 8% over the study. Over the study, 38% of the plants died, with most mortalities occurring during two peak periods of rodent activity. All possible transitions occurred between the four stage classes with most aboveground plants tending to stay in the same class from year to year. Retrogressions from the larger stemmed plant stages to the smaller rosette stage were documented and increased during periods of environmental stress, i.e., rodent activity and fire. Fire caused high mortality of moss and lichens. Recruitment remained low for three years following the fire; however, it increased markedly as moss and lichens began to re-establish at the end of the study. We identified several detectability problems associated with the time of monitoring. All aboveground plants were present and detected at early sampling, however, by late sampling at flowering time, 48% of plants present early had disappeared or were undetectable or unidentifiable. Detectability of all aboveground stage classes declined considerably by flowering time (time-dependent) and affected the small, ephemeral, rosette stage disproportionately (stage-dependent). The early season sampling period was critical for discovering new life history and demographic information for this species, revealing several detectability problems associated with this species, and obtaining unbiased demographic information.