Vegetation inventory, mapping, and characterization report, Gila Cliff Dwellings National Monument

Studd, Sarah; Galvin, Jeff

From 2012 to 2015, the Sonoran Desert Network conducted vegetation mapping and characterization at Gila Cliff Dwellings National Monument (NM) over several separate phases. This effort was completed under the National Park Service (NPS) Vegetation Mapping Inventory, which aims to complete baseline mapping inventories at over 270 NPS units. The goal of the project was to provide park managers with a digital map product that meets national standards of spatial and thematic accuracy, while also placing park vegetation into a regional and national context. The data standard was designed to facilitate the production of uniform statistics about vegetation across the nation, enable the translation of data collected at various scales, and allow data sharing, aggregation, and comparison across regions. Vegetation mapping and characterization comprised four major phases: (1) field-based vegetation classification data collection, (2) field-based mapping from aerial imagery (map unit delineation), (3) development of vegetation community types at the National Vegetation Classification System (NVCS) association level, and (4) map thematic accuracy assessment. Phase 1 and the majority of phase 2 were completed during summer 2012, with some additional mapping during summer 2013. Community-type descriptions were subsequently drafted to meet the NVCS standard and applied to each mapped area. This classification was developed concurrently from plot data and field-censused polygon data (map units). Concurrent with the additional mapping in 2013, network staff conducted a thematic validation effort, providing additional data that improved both the detail of the association descriptions and the accuracy of the mapped polygons. A formal accuracy assessment was completed in summer 2015. In the accuracy assessment, plots were distributed proportionally within each vegetation type and sampled by a separate team in an unbiased manner. Following accuracy assessment, final products were developed. Those products include this report, a digital map, and full vegetation descriptions. Gila Cliff Dwellings NM covers 213 hectares (527 ac) and consists of two separate units: the main unit (196 ha/485 ac) and the TJ unit (71 ha/42 ac), separated by two kilometers of U.S. Forest Service (USFS) lands. To provide more useful mapping products, an additional 833 hectares (2,060 ac) of USFS land, as well as the state-administered Heart Bar Wildlife Area, were included in this mapping project. This allowed us to connect the two units of the park and provide an ecologically meaningful buffer around them, for a total of 1,047 hectares (2,587 ac). Management of these lands is highly coordinated across the partners, so an integrated map was more useful for meeting shared natural resource goals. To accurately assess, classify, and describe the monument’s previously undescribed vegetation communities, it was necessary to sample the larger watershed area. This helped ensure we captured the variation within each community and were sampling at the community level, rather than just individual stands. The project area covers a complex landscape of topography, geology, and hydrologic influence. It was also greatly affected by the 2011 Miller Fire and subsequent flooding. A total of 16 distinct communities were described and mapped at Gila Cliff Dwellings NM. These ranged from lush riparian woodlands lining the west and middle forks of the Gila River, dominated by narrowleaf cottonwood (Populus angustifolia) and dewystem willow (Salix irrorata); to drier upland woodlands and tree savannas dominated by two-needle pinyon (Pinus edulis) and alligator juniper (Juniperus deppeana), with an understory of blue grama (Bouteloua gracilis). Overall accuracy for all classes was 86.7% (90% CI: 83.2, 90.2), with a Kappa (a measure of overall accuracy minus chance agreement) of 83.7% (90% CI: 80.0, 87.4). Individual accuracies ranged from 57.7% to 100%.

Vegetation inventory, mapping, and characterization report, Gila Cliff Dwellings National Monument

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