Grand Canyon National Park-Grand Canyon / Parashant National Monument vegetation classification and mapping project

Kearsley, Michael; Green, Kass; Turkman, Mark; Reid, Marion; Hall, Mark; Ayers, Tina; Christie, Kyle

Ecologists and botanists from NatureServe, Northern Arizona University and the National Park Service created the vegetation classification based on 1496 vegetation classification plots within the mapping area. Vegetation data from a USGS data set provided guidance on classification of riparian vegetation in the Colorado River Corridor which was not sampled for this project. Map calibration and accuracy assessment data identified two communities which had not been documented during the initial classification data collection. The final classification included 222 NVC Association-level plant communities. Of these, 139 represented existing Associations, 47 required the creation and description of new Associations, and four represented NVC Alliance-level communities. The 32 remaining communities were considered “Park Specials” because, although unique and outside the described boundaries of existing Alliances, they lacked sufficient information and abundance to justify creating new Associations. A dichotomous key to the vegetation Associations was created by and tested by NatureServe, Northern Arizona University and KGA personnel both in the field and using existing data sets. The classification work done for this project demonstrated both the strengths of using a dynamic standard like the NVCS, and the challenges it presents. Many of the described Associations represented refinements of types described from more limited geographic areas. The Goodding’s willow Woodland had been described from samples in New Mexico and Texas, where mesquite and ash trees were common associates, rather than the tamarisk and willow-leaf Baccharis which are associates in Grand Canyon. Similarly, descriptions of new Associations like the Crucifixion-thorn Grand Canyon Shrubland are likely to be revised and renamed when they are analyzed from the many other parts of the southwestern U.S. where they occur. Furthermore, during the course of this project, the botany underlying the classification was undergoing its own changes; the desert Ceanothus (Ceanothus greggii) in Arizona will be moved to Mojave Ceanothus (C. vestitus) and Emory Baccharis (Baccharis emoryi) has been synonymized with B. salicina. Both of these changes will eventually require updates to the USNVC as soon as the process defined by the NVCS is completed. The final map contained 87 map classes with a minimum mapping unit of 0.5 hectares across more than 560,000 hectares. The classes included 41 NVC Associations, 36 NVC Alliances, seven NVC Group-level classes and three classes of unvegetated surfaces (built-up, water, and bare soil/rock). Accuracy assessment (AA) was done for 1847 map segments, distributed based on map class abundances. Accuracy by map class varied between 13% (Pinyon – Juniper / Talus or Canyon Slope Scrub) and 100% (Douglas Fir / Snowberry Forest and 5 others); project-wide accuracy was 77%. Roughly one-third of the mis-identified samples were among closely– related vegetation types. Others were among classes which were found in similar habitats (e.g., constrained tributary beds) and had very similar spectral signatures.

Grand Canyon National Park-Grand Canyon / Parashant National Monument vegetation classification and mapping project

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