National Parks and Monuments are not immune to exotic plant species’ negative impacts on natural resources and visitor experience. Exotic plant species modify native landscapes and natural disturbance regimes.  Aztec Ruins National Monument was established in 1923 to preserve ancient Pueblo structures and artifacts. The use of Park land historically for agricultural and grazing purposes and more recent development and gas wells surrounding the Park have all contributed to the establishment of exotic plant species.  The objective of this study was to quantify if exotic plant species differed among various land cover types and soil disturbance levels within the Park.  Fifty-six grid cells, each approximately two ha in area, were classified into six land cover types.  Within each grid cell, we established a variable width belt along a 50-m transect and we assigned all exotic species within each belt a cover class percentage.  In addition, we surveyed the entire grid cell to identify any additional exotic species.  We also measured environmental variables and took photos along each 50-m transect.

Results/Conclusions

Total exotic plant cover was 27%. Kochia scoparia (common kochia) had the highest (7.4%) plant cover for the entire Park.  Five other exotic species had an average plant cover over one percent: Bromus inermis (smooth brome) at 4.3%, Elaeagnus angustifolia (Russian olive) and Salsola tragus (Russian thistle) at 3.5% each, Thinopyrum intermedium (intermediate wheatgrass) at 2.1% and Carduus nutans (musk thistle) at 1.1%. The Riparian/Floodplain land cover type had the highest average exotic plant cover followed by the Old Fields/Cultivated Lands cover type.  We found a total of 57 exotic species within the 56 grid cells.  Eight exotic species had frequency values of 50% or higher meaning that these individual species were found in more than half of the 56 grid cells.  Bromus tectorum (cheatgrass) had the highest frequency of 94.6.  Soil disturbance was highest in the Orchards land cover type and lowest in the Uplands/Slopes land cover type.  The best method to manage exotic species is to prevent their establishment and spread by avoiding management actions that encourage invasion and to monitor for exotic species each year. There is no one optimum method for controlling and eradicating all exotic species.  The establishment of self-sustaining native plant communities is one of the most effective methods to prevent future exotic plant invasions and should be the ultimate goal of any restoration efforts to remove exotic species.