National Park Service Vegetation Inventory Program: Grand Portage National Monument, Minnesota

Hop, Kevin; Lubinski, Sara; Dieck, Jennifer; Menard, Shannon; Drake, Jim; Faber-Langendoen, Don

Photointerpreters, ecologists, and botanists collaborated to identify and describe vegetation types within the National Vegetation Classification Standard (NVCS) and to determine how best to map them by using aerial photographs. The team collected 23 vegetation sampling plots within the GRPO project extent. Furthermore, data from 147 accuracy assessment (AA) sites were collected (of which all were used to test accuracy of the vegetation map layer). These data sets led to the identification of 20 vegetation associations in the NVCS at the GRPO. Additional vegetation types are recognized at the group level in the NVCS. A total of 35 map classes were developed to map the vegetation and general land cover of GRPO and environs, including the following: 31 map classes representing natural/semi-natural vegetation types at various levels in the NVCS, one map class representing cultural vegetation (e.g., developed) in the NVCS, and three map classes representing non-vegetated units (e.g., open water bodies). Features were interpreted by using high-quality stereoscopes over light tables and 1:12,000-scale, color-infrared aerial photographs dated October 2006 (during fall leaf change). Polygon units were mapped to a 0.25-ha minimum mapping unit. An ancillary set of 1:8,000-scale, true-color aerial photos dated May 2003 (during leaf-off conditions) covering the entire GRPO lands were used for additional reference during mapping. The interpreted data were digitally and spatially referenced, making the spatial database layers usable in a geographic information system. A geodatabase containing various feature class layers and tables show the locations of vegetation types and general land cover (vegetation map), vegetation plot samples, AA sites, project boundary extent, and aerial photographic centers. The feature class layer for the GRPO vegetation map provides 423 polygons of detailed attribute data covering 291.8 ha, with an average polygon size of 0.7 ha. Of the area mapped, 413 polygons (97.6%) represent natural/semi-natural types in the NVCS, encompassing 279.2 ha (690 acres; 95.7%) of the total map extent. Summary reports generated from the vegetation map layer indicate that forest types dominate the vegetation landscape (types from the NVCS), populating 93.7% of the polygons and covering 96.5% of the area, and are largely dominated by Spruce - Fir - Aspen Forest and Aspen - Birch / Boreal Conifer Forest associations. Although not common throughout the GRPO, the White-cedar - Boreal Conifer Mesic Forest association was mapped more frequently on the westward end. The White Pine / Mountain Maple Mesic Forest association was mapped intermittently throughout the GRPO. Some associations were mapped only to the Lake Superior area around Preface viii the village of Grand Portage, including Jack Pine / Balsam Fir Forest, Boreal Pine Rocky Woodland, and Boreal Hazelnut - Serviceberry Rocky Shrubland. Several other ruderal vegetation types growing in response to the human history of this area were also mapped. An herbaceous wetland association—Water Horsetail - Spikerush Marsh—was mapped only to the Pigeon River at the opposite end of the GRPO. A thematic AA study was conducted of map classes representing floristic types within the NVCS. Results present an overall accuracy of 91.8% (Kappa index of 90.7%) based on data from 147 AA sites. Most individual map-class themes exceed the NPS VIP standard of 80%, with a 90% confidence interval.

National Park Service Vegetation Inventory Program: Grand Portage National Monument, Minnesota

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