Plant community composition and structure monitoring for Devils Tower National Monument: 2011-2015 summary report

Ashton, Isabel; Davis, Christopher

The Northern Great Plains Inventory & Monitoring Program and Fire Effects Program have been monitoring vegetation in Devils Tower National Monument (DETO) for over 18 years. While methods have changed slightly, this report summarizes data from 57 locations from 1998 to 2015. Below, we list the questions we asked and provide a summarized answer. For more details see the full report. A summary of the current condition (2011-2015) and trends (based on 1988-2015) in plant communities at DETO is found in the natural resource condition table below. 1. What is the current status of plant community composition and structure of DETO grasslands (species richness, cover, and diversity) and how has this changed from 1998 to 2015? The ponderosa pine woodlands, mixed-grass prairie, and riparian plant communities within the boundaries of DETO are characterized by low to moderate native species richness. The riparian areas generally maintain a lower species richness and higher exotic cover than the upland areas. The highest plant species richness was found in the prairie dog town. We found no significant trends in native diversity or evenness from 1998 to 2015, but both are threatened by the increasing cover of annual bromes. Annual bromes are an emerging threat in DETO, and keeping them in low abundance will help maintain native plant diversity. Other exotics, such as Kentucky bluegrass, are more prevalent, but there is no evidence of an increasing trend in their cover. 2. How do trends in grassland condition correlate with climate and fire history? The large variability in DETO’s climate makes it difficult to discern strong patterns linking temperature, precipitation, and plant community structure (e.g. exotic cover, diversity). Plant height increased in years with more total precipitation but we found no other significant relationship between climate and vegetation. A longer time series of vegetation data will make it easier to elucidate trends in the future. DETO has been using prescribed burning as a management tool since the 1980s. We found that there was no difference in native diversity or exotic cover among plots that had burned recently and those that had not burned for longer time periods. This suggests that prescribed burning is not having a large effect on herbaceous vegetation in DETO. 3. What, if any, rare plants were found in DETO long-term monitoring plots? We identified nine rare plant species in DETO between 1998 and 2015; eight of these are considered critically imperiled within Wyoming. These plants are found in such low abundance and in such few plots, it is unlikely that plant community monitoring will be able to detect any trends in rare plant abundance. We recommend more targeted surveys of rare plant species of concern be completed when funds are available.

Plant community composition and structure monitoring for Devils Tower National Monument: 2011-2015 summary report

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