NLCD shrub component historical products characterize the percentage of each 30-meter pixel in the Western United States covered by shrub, sagebrush, herbaceous, annual herbaceous, litter and bare ground for each year from 1985-2018 - providing change trends for 33 years (imagery for 2012 was unavailable). Because of file size limitations, individual component products are packaged in three historic intervals including 1985-1995, 1996-2006, and 2007-2018. Trend analysis for each component is also available as a zip file for the full 1985-2018 period to help users understand the magnitude of change.
Trend products in the zip file include slope, standard error and t-statistic calculated from least squares linear regression. The slope represents the average percent cover change per year over the times-series, the standard error measures the departure from the linear slope model across all yearly observations in each pixel and the t-statistic reflects the confidence of change in each pixel.