This dataset includes a polygon vector shapefile that provides information pertaining to the sampling universe (i.e., the potential sampling units within the study area) from which nest sampling areas were selected.
To delineate sampling units (i.e., survey areas), we overlaid the northwest portion (i.e., northwest of the Marsh Creek Anticline) of the 1002 Area of the Arctic NWR with a grid of 16 ha plots (400 × 400 m each) in ArcGIS 10 (Environmental Systems Research Institute, Redlands, CA, USA; Alaska Albers Equal Area Conic NAD83). Given the logistical constraints for obtaining permission to access private lands within the Arctic NWR, we limited our spatial sampling to public lands administered by the U.S. Fish and Wildlife Service using the National Wildlife Refuge Land Status Data for Alaska (U.S. Fish and Wildlife Service 2014). This process resulted in a total of 11,913 plots or 1,906 km2 as potential sampling units.
Information for each potential sampling area includes location, percentage of habitat classifications (obtained from Jorgenson, J. C., P. E. Joria, T. R. McCabe, B. R. Reitz, M. K. Raynolds, M. Emers, and M. A. Wilms. 1994. Users guide for the land-cover map of the coastal plain of the Arctic National Wildlife Refuge. U.S. Fish and Wildlife Service, Fairbanks, Alaska, USA), and stratum.
To delineate strata for each sampling unit, we used a previous habitat classification for the Arctic NWR (Jorgenson et al. 1994). Similar to Brown et al. (2007), we created four habitat strata (wetland, moist, riparian, upland); by combining similar habitat categories from the Jorgenson et al. classification (wetland: ‘wet sedge tundra’ + ‘wet/moist sedge tundra with 10-50% wet inclusions’; moist: ‘moist sedge-willow tundra with 10-50% wet inclusions’ + ‘moist sedge-willow tundra’ + ‘moist sedge-dryas tundra’; upland: ‘moist sedge tussock tundra’ + ‘moist shrub tussock/watertrack’ + ‘moist shrub tundra on high-centered polygons’ + ‘moist shrub tundra’ + ‘dryas-graminoid alpine tundra’; riparian: ‘riparian shrub’ + ‘dryas river terrace’ + ‘partially vegetated’ + ‘barren’). Habitat strata was assigned to plots based on which habitat comprised the greatest percentage of the plot. In strata calculations water (‘water’ + ‘ice’) and unclassified (‘shadow’ + ‘unprocessed pixel due to poor quality data’) were excluded.
The data providers have invested considerable effort in QA/QC, but it is possible that undetected errors remain. It is strongly recommended that careful attention be paid to the contents of the metadata file associated with these data to evaluate data set limitations, restrictions or intended use. The originators of this dataset shall not be held liable for improper or incorrect use of the data described and/or contained herein.
Potential users of these data should first contact the data authors listed below, as potential biases may occur within the data depending on the intended use. Therefore, potential users should contact the data authors to discuss intended use and how these data may or may not be applicable.
General field methods are available in annual protocol documents that detail specific annual methodologies.
