Normalized difference vegetation index data for Saddle snowfence, 1994.

A snowfence was built in 1993 on the Niwot Ridge Saddle grid to determine the effects of changes in snowpack on a number of variables, one of which was vegetation greenness (measured through the normalized difference vegetation index). The study area of the snowfence was 60m x 125m. Spectral data in the red and near infra- red bands were recorded at sixty plots (points) in four rows located approximately at 10, 25, 45, and 75 meters east of the fence (the drift area). The plots were marked with thin wire stakes put into the ground and flagged (for visibility) and given aluminum tags with their plot identification code. All the plots were located in Kobresia myosuroides communities. In each row there were ten plots located in control areas just to the north and south of the area affected by the snowfence -- five to the north and five to the south -- and five plots located in the drift area of the snowfence. The individual plots were broken into groups of five according to their location (i.e., their distance from the fence (row), and location within their row (north, south, or within the snowfence area)). Within each of these groups, the plots were given a number starting with one and going to five. The plots were then given unique codes made up of plot type (c for control and sf for snowfence), location within a row (for the control plots only - n for north and s for south), the distance in meters of the row from the snowfence (10, 25, 45, or 75), and the number that uniquely identifies each plot within a group (one through five). For example, the code cn10_1 represents plot number one of the group of control plots north of the snowfence and 10 meters east of the snowfence. The location of each plot was measured as set of coordinates within the snowfence area. The southern terminus of the snowfence was used as the origin, with the y-axis running along the snowfence and the x-axis running perpendicular to the snowfence at it's southern end. The first coordinate was the distance in m from the y-axis in an easterly direction, and the second coordinate was the distance in m from the x-axis in a northly direction. Note that the 10, 25, and 45 meter rows are actually at roughly 15, 30, and 50 meters east of the snowfence whereas the 75 meter row is actually at 75 m. east of the snowfence. It is also important to note that the plots are not necessarily in numerical order in each row, and that the x and y locations were only approximately measured.