Vegetation classification and mapping project report, Glen Canyon National Recreation Area and Rainbow Bridge National Monument

Tendick, Amy; Spence, John; Reed, Marion; Shulz, Keith; Kittel, Gwen; Green, Kass; Wight, Aneth; Wakefield, Gery

The Northern Colorado Plateau Inventory and Monitoring Network (NCPN) worked with the support of the NPS Vegetation Mapping Inventory Program (VMI) to inventory, classify, describe, and map vegetation at Glen Canyon National Recreation Area and Rainbow Bridge National Monument (GLCA/RABR). This collaborative effort involved many project partners, particularly GLCA/RABR park staff, the Western Region office of NatureServe, Northern Arizona University (NAU), and Kass Green Associates. The mapping area is approximately 505,642 hectares (1,249,468 acres), encompassing Rainbow Bridge National Monument, at 65 hectares (160 acres), as well as Glen Canyon NRA. Guided by a gradsect analysis created by Kass Green Associates, vegetation classification plot and observation point data were collected over three field seasons (2011–2013). A portion of GLCA in the Orange Cliffs section had previously been sampled in the fall of 2004 by NCPN ecologists as part of the Canyonlands National Park vegetation mapping effort. Field crew members collected vegetation and environmental data from 1,164 vegetation classification plots and 51 observation points from 2004 and 2011–2013. Using various multivariate statistical and tabular tools, and adhering to the guidelines of the National Vegetation Classification Standard (NVCS),vegetation plot data were analyzed by NCPN, GLCA/RABR, and NatureServe ecologists and revealed 193 National Vegetation Classification (NVC) plant associations for GLCA/RABR, representing 80 NVC alliances and 35 NVC groups. The final assignment of plots to associations of the NVC Standard and the local and global plant association descriptions, based on the classification, were completed in 2014, with minor revisions through August 2016. A full summary of this work is described in the Vegetation Classification and Description section of this report. Aerial photointerpretation was conducted by the Project Manager with the help of an assistant mapper between the fall of 2012 and fall of 2014, using the 2009 1-meter spatial resolution National Agriculture Imagery Program (NAIP) imagery for the Utah portions of GLCA, and the 2010 1-meter spatial resolution NAIP for the Arizona portions of GLCA as the base image layers. The project used the program standard minimum mapping unit (MMU) of 0.5 ha with few exceptions. The majority of the mapping work was performed using ArcGIS editing tools and onscreen, heads-up digitizing, aided by ancillary datasets. Map classes were defined for the project by the primary photointerpreter (PI) with input from the GLCA Chief Scientist. A draft vegetation map and associated spatial database were completed for the Orange Cliffs section of GLCA in the summer of 2014 and for the remainder of GLCA/RABR in the late fall of 2014. Forty-eight map classes represented by 33,691 polygons were developed for GLCA/RABR. A total of 31,058 polygons represent 37 natural or semi-natural vegetation map classes covering 75% of the mapping project area. Eleven additional land use/land cover and geologic map classes describe 2,633 polygons (25% of the area). Average polygon size across all map classes is 23.1 ha (57.2 acres). Blackbrush Shrublands had the highest number of polygons (5,560) polygons covering 14.5% of the total vegetated mapping area. The Pinyon - Juniper Sandstone Woodland Complex is the most extensive map class, delineated on 76,373 ha (188,722 acres) or 20.1% of the vegetated mapping area. A full summary of this work is described in the Vegetation Mapping section of this report. Assessment of map accuracy entailed sampling an additional 1,668 data plots between 2014 and 2015. Field crews were guided by a dichotomous key to the vegetation associations created for the project using the classification (Appendix G). Accuracy assessment (AA) data were analyzed, with results tabulated into a contingency matrix.

Vegetation classification and mapping project report, Glen Canyon National Recreation Area and Rainbow Bridge National Monument

Series

Collections