Inventory of Exotic Plant Species Occurring in Aztec Ruins National Monument

Korb, Julie

For national parks in the Southern Colorado Plateau Inventory and Monitoring Network, the first step to controlling exotic plants is to complete an exotic species inventory. The inventory results may then be combined with other information to prioritize which exotic species should be controlled first based on their invasiveness and/or feasibility of control and to prioritize which park areas should be controlled first based on their conservation status and/or restoration potential. The objectives of this project were to complete an exotic plant inventory, collect voucher specimens for new exotic species in the park, and write a report on exotic plant species occurring in Aztec Ruins National Monument. Sampling followed a systematic, grid-based approach to ensure rapid and repeatable data collection. Within each grid cell, a diagonal 50-m transect, along which vegetation and environmental data was collected, was mapped through the cell center. The inventory was conducted from June to July 2008 during the peak-growing season. In late July and August, a general resurvey of the area was completed to determine if any new species had emerged since sampling. Each of the 56 grid cells was classified into one of six land use types: Core Cultural Area, Farmer’s Ditch, Old Fields/Cultivated Lands, Orchards, Riparian/Floodplains, and Uplands/Slopes. The botanist documented the exotic species along the 50-m variable width belt transect and assigned a cover class for each exotic species. A GPS was then used to walk the perimeter and the area inside the entire grid cell to identify any additional exotic species found within the grid cell but not within the 50-m variable width belt transect. Soil samples were collected and aspect, slope, tree canopy cover, and soil disturbance were measured. Total exotic plant cover in Aztec Ruins National Monument was 26.98%. Kochia scoparia (common kochia) had the highest overall plant cover for the entire park—an average of 7.43%. The Riparian/Floodplain land use type had the highest average exotic plant cover with 76.7% cover. We found a total of 39 exotic species within the 56 belt transects, which contained a total of approximately 1 ha sampled area, and 57 exotic species within the 56 grid cells, which contained a total of approximately 112 ha sampled area. The average number of exotic species within the 56 belt transects was 4.4 species and 13.1 species in the grid cells. The Orchards land use type had the highest average number of exotic species for both the belt transects and grid cells followed by the Core Cultural Area, Old Fields/Cultivated Lands, Riparian/Floodplain, Farmer’s Ditch, and Uplands/Slopes land use types.

Inventory of Exotic Plant Species Occurring in Aztec Ruins National Monument

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