Vegetation mapping inventory project: National Park of American Samoa

Green, Kass; Kittel, Gwen; Lopez, Chad; Ainsworth, Alison; Selvig, Meagan; Vaivai, Visa; Akamine, Kathryn; Tukman, Mark; Kudray, Greg

This report details the methods used and results of the vegetation inventory for The National Park of American Samoa (NPSA). NPSA’s unique ecosystems span 5500 ha (13,590 ac) on the Samoan Islands of Tutuila, Ofu, and Ta‘ū and include approximately 1600 ha (4000 ac) acres of coral reef and ocean. While Congress has authorized the inclusion of portions of Olosega into the park, the Olosega lands have not yet been added to the current land lease agreement. However, because this project included mapping the proposed park areas of Olosega, the report also includes the work done on Olosega. The park’s dynamic landscape, and extreme range of elevation and climate combine to create a distinctive and exciting national park. The vegetation inventory was a team effort managed by the National Park Service (NPS), Pacific Island Network Inventory and Monitoring Program (PACN), and staffed by personnel from the NPS, University of Hawaii (UH), Cogan Technology, Inc., NatureServe, and Kass Green & Associates (KGA). The NPS collected 136 vegetation classification plots and observation sites. NatureServe used these data to create a key and descriptions for 17 vegetation associations at NPSA. To ensure data compatibility throughout the NPS and other agencies the National Vegetation Classification Standard, Version 2 was used to characterize NPSA’s vegetation. Quickbird, Ikonos, Worldview2 and digital airborne optical and lidar imagery of NPSA were obtained from NOAA and the US Department of Agriculture – National Resource Conservation Service (USDA - NRCS). The imagery was segmented in eCognition software and both the imagery and the segments were taken to the field to support the calibration trip. Following the calibration trip, KGA labeled the segments using the imagery, ancillary data sets, and classification and regression tree analysis to create a preliminary map. The preliminary map was reviewed by PACN staff and manual edits based on the comments were made to the preliminary map to create NPSA’s draft vegetation map. PACN personnel collected 249 accuracy assessment (AA) samples of NPSA’s vegetation. The sample reference labels were compared to the draft map labels at each sample location to create an error matrix. Because of confusion in the registration of the imagery and in the AA, a validation trip was undertaken by KGA, NPSA, UH, and PACN staff. As a result, the draft map was reregisterd to the 2012 airborne imagery. Overall draft map accuracy of NPSA is 68% using the primary reference label, and 70% when the secondary label is accepted. Using the AA results and the results of the validation trip, PACN and KGA personnel decided which associations would be collapsed into map classes for creation of NPSA’s final vegetation map, resulting in 23 vegetated and three unvegetated map classes. The draft map was extensively manually edited using the new high resolution airborne imagery for errors discovered during AA and the validation trip, and the final map was delivered.

Vegetation mapping inventory project: National Park of American Samoa

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