National Park Service


Date of this Version



Natural Resource Report NPS/NGPN/NRR—2016/1198 / NPS 165/132284, April 2016: viii, 36 pages

Published by the United States Department of the Interior, National Park Service, Natural Resource Stewardship and Science, Fort Collins, Colorado

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Please cite this publication as:

Ashton, I. W. and C. J. Davis. 2016. Plant community composition and structure monitoring for Agate Fossil Beds National Monument: 2011-2015 summary report. Natural Resource Report NPS/NGPN/NRR—2016/1198. National Park Service, Fort Collins, Colorado.


United States government work. Public domain material.


Executive Summary

The Northern Great Plains Inventory & Monitoring Program and Fire Effects Program have been monitoring vegetation in Agate Fossil Beds National Monument for over 18 years. While methods have changed slightly, this report summarizes data from over 80 locations from 1998-2015. We use these data to explore status and trends in upland and riparian plant communities, the occurrence of rare plants, and the effects of the Fossil Hills trail installation on the surrounding vegetation. A summary of the current condition (2011-2015) and trends (based on 1998-2015) in plant communities at Agate Fossil Beds NM (AGFO) is found in Table ES-1.

1. What is the current status of plant community composition and structure of AGFO grasslands (species richness, cover, and diversity) and how has this changed from 1998 to 2015?

Native grasses, such as needle and thread, sand reed, and western wheatgrass, are abundant and the dominant component of the prairie at AGFO. Native plant diversity is at a moderate level compared to other grasslands in the region (Table 7), but diversity is spatially variable. We found no significant trends in native diversity or evenness from 1998 to 2015, but both may become threatened if cover of annual invasive brome grasses increases, as we’ve observed in other Northern Great Plains Inventory and Monitoring units (Figure 8).

2. How do trends in grassland condition correlate with climate and fire history?

Native species richness increased in years with more rainfall and a hot dry year in 2012 corresponded to large declines in native species richness and an increase in exotic species cover. Plots that had not burned in 5 or 6 years had a higher number of native species and a lower cover of exotics than sites that burned more recently and when compared to AGFO averages (Figure 12). This suggests that prescribed fire can benefit the mixed-grass prairie in AGFO, but it may take 5 or more years to see the positive effects following a burn.

3. What, if any, rare plants were found in AGFO long-term monitoring plots?

We identified 22 rare plant species in AGFO between 1998 and 2015; seven of these are considered critically imperiled within Nebraska. We recommend monitoring of rare plant populations and more targeted surveys of rare plant species be completed when funds are available.

4. How did installation of the AGFO Fossil Hills Trail affect the adjacent prairie?

The disturbed prairie adjacent to the Fossil Hills Trail is very similar to the native prairie in other parts of AGFO. This suggests that the prairie in AGFO is resilient and can recover from a moderate level of disturbance. We suggest continued monitoring of these plots to ensure that any increase in exotic species abundance is detected so appropriate control measures can be taken.

5. What is the composition and structure of the riparian corridor at AGFO?

The riparian corridor in AGFO is a fairly diverse assemblage of riparian species such as sedges, willows, and cattails. It is, however, more invaded than the upland areas of AGFO and threatened by high cover of Kentucky bluegrass and pale yellow iris. Since riparian monitoring began in 2012, we have not detected a significant change in the cover of pale yellow iris. Continued monitoring is necessary to determine if exotic treatment is effective over the long-term.