摘要：Analysis of coarse resolution (~1 km) satellite imagery has provided evidence of vegetation changes in arctic regions since the
mid-1980s that may be attributable to climate warming. Here we investigate finer-scale changes
to northern vegetation over the same period using stacks of 30 m resolution Landsat TM and
ETM + satellite images. Linear trends in the normalized difference vegetation index (NDVI) and
tasseled cap indices are derived for four widely spaced national parks in northern Canada.
The trends are related to predicted changes in fractional shrub and other vegetation
covers using regression tree classifiers trained with plot measurements and high
resolution imagery. We find a consistent pattern of greening (6.1–25.5% of areas
increasing) and predicted increases in vascular vegetation in all four parks that is
associated with positive temperature trends. Coarse resolution (3 km) NDVI trends
were not detected in two of the parks that had less intense greening. A range of
independent studies and observations corroborate many of the major changes
observed.
