Vegetation classification and mapping project report: Great Sand Dunes National Park and Preserve

Salas, David; Stevens, Joe; Schulz, Keith; Artmann, Mike; Freisen, Beverly; Blauer, Steve; Schweiger, E.; Valdez, Andrew

This vegetation classification and mapping effort encompasses 167,148 ha(413,031 acres ) within the San Luis Valley, west of the Sangre de Cristo Mountains in south central Colorado. The mapping boundary is made up of several management units from a variety of government and private agencies (and a small amount of private property). These include the National Park Service (Great Sand Dunes National Park and Preserve – 60,354 ha, 149,137 acres), U.S. Fish & Wildlife Service (Baca National Wildlife Refuge – 37,483 ha, 92,623 acres), U.S. Forest Service, Bureau of Land Management (Blanca Wetlands), and the Nature Conservancy (Medano-Zapata Ranch – 13,243 ha, 32,725 acres). The mapped area includes portions of Saguache and Alamosa Counties. The actual mapping boundary reflects the U.S. Forest Service fire management plan area and is thus an effort by the NPS-USGS mapping program to encompass not only lands within the NPS but also those that are in proximity and that have some type of ecological or management cohesiveness. This mapping effort is part of the National Park Service national inventory and monitoring program and will provide core or 'baseline‘ information that park managers need to effectively manage and protect park resources. This vegetation inventory was conducted in accordance with specified protocols and quality assurance standards. Data obtained through this inventory are compatible with other efforts, allowing for synthesis and analysis at broader levels. To classify the vegetation, we sampled 603 representative plots and 208 observation points during the summers of 2005 and 2006 over the entire mapping area. Analysis of the plot data using ordination and clustering techniques produced 198 distinct plant associations, 22 of which are newly described. These associations were then combined into 51 vegetated map units. Other map units not derived from plot data include sparsely vegetated, non-vegetated, and various cultural features such as roads, urban and farmed lands. The digital vegetation map was produced using a combination of machine processing and visual interpretation. We used two primary image sources. These included 2006 1:12,000-scale infrared aerial photography for the areas west of the Sangre de Cristo Mountain range that was subsequently processed by the USFWS and 2006 National Agricultural Imagery Program (NAIP) imagery, and ground-truthing to interpret the complex patterns of vegetation and landuse at GRSA. Other referenced imagery included 2006 and 2007 Quickbird imagery which covered portions of the project area. All of the interpreted and remotely sensed data were converted to Geographic Information System (GIS) databases using ArcInfo© software. Draft maps created from the vegetation classification were field-tested and revised before independent ecologists completed an assessment of the map‘s accuracy during 2008. During the summer of 2008 we sampled 1,537 accuracy assessment points to establish a final overall accuracy of 73.7%. This metric is subject to considerable interpretation and is discussed in detail in the results section.

Vegetation classification and mapping project report: Great Sand Dunes National Park and Preserve

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