Vegetation inventory project report: City of Rocks National Reserve

Erixson, John; Cogan, Dan

A three-year, three-phase program was initiated to complete the tasks of sampling, classifying, and mapping the plant associations and vegetation alliances within City of Rocks National Reserve (CIRO). Phase-one, resulted in the plant association and vegetation alliance classification using the National Vegetation Classification System (NVCS). Vegetation classification was based on the 2009 field sampling of 190 representative classification plots located within the boundary of CIRO and adjoining Castle Rocks State Park. Analysis of the classification plot data occurred in 2010. Through this process 35 distinct plant associations were identified as were two vegetation alliances. Vegetation alliance and plant association local descriptions and a field key to determine each association in the field are included in this report. Phase-two, resulted in creation of the digital vegetation and land use map and project geodatabase. Mapping was conducted primarily by interpreting vegetation-specific and non-vegetated site signatures from the 2009 National Aerial Imagery Program (NAIP) ortho-photo products. CTI reliably discerned 34 vegetation, 10 land use/land cover, and one geology/sparse vegetation map units. The mapping process relied on manual digitizing of homogenous photo-signatures supported by on-site verification. All interpreted data were converted to Geographic Information System (GIS) databases using ArcGIS software. The final map layer contains vegetation, land-use, and geologic exposure polygons with corresponding map class, NVC, and modifier attributes. Draft maps were printed, field tested, reviewed, and revised based on the field observations. Following verification, edits were applied to create the final vegetation map product for accuracy assessment (AA). In Phase-three the AA was conducted during the 2010 field season. Sampling required selecting 597 random point locations throughout the study area based on frequency and abundance for each vegetation map unit. AA locations were accessed, the vegetation at each target was keyed to the proper association, and representative photographs of each location were acquired. The field data were compared to the electronic vegetation map following the final assessment and three map units with low accuracy were combined with similar map units to increase the accuracy. The AA analysis on the modified vegetation layer revealed an overall thematic accuracy of 88%. Completion of the project in Phase-four included producing the standard project deliverables as described and presented in this report.

Vegetation inventory project report: City of Rocks National Reserve

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