Winter satellite images always provide a completely different perspective of ecosystems and landscapes. The Blue Marble images of NASA's WorldWind can be used to demonstrate this point. This March 2004 composite image shows the physiographic and ecological zones of Canada and parts of the US. The transition from the bare Prairies through the tree covered dark grey Boreal zone, the sparsely vegetated sub arctic (light grey) and the bare arctic is clearly visible. In essence this is an image reflects the density of vegetation and trees.
Figure 1 Winter Image March 2004, NASA Blue Marble
Figure 2 Enlarged Portion of the above image.
While the small scale version above shows the ecological zones, the more detailed image shows the intricate vegetation pattern developed as result of a long wildland and forest fire history. The white snow cover underneath the vegetation cover actually enhances visualization of formerly burned areas. Typically the most recent burns are devoid of vegetation and show as white patches. Older burns can be "dated" based on the darkness of the grey patches: the darker is usually older.
Figure 2 NASA 2000 Landsat Psuedo Color Image. This WorldWind image shows the same area with a false colour satellite image. The near infrared shows the very young fire regeneration (1-3 years) after the burn in deep red colours. Older regrowth after fires show as pinks, and areas burned more than 10 years ago will start to look green again.
Figure 3 NASA
1990 Landsat Psuedo Color Image. This composite satellite image shows a totally different the fire pattern 10
years earlier in 1990. It is interesting to see that most of the
red areas in the south western part of the image (mid boreal
zone)have turned from red (below) to green on the image above. In
the north
eastern
half
which (the north boreal and subarctic zone) the recuperation of
the vegetation cover is different and many areas are still pink 10
years later.
Figure 4 Google Earth Perspective. The image below shows the abundance of recent and old fires as well, but the distinct pattern is partly obscured by the strips of high resolution imagery. Still it is clear that in the period of about 20 years covered by these satellite images over 50% of this area was burned. While most of the fires are probably the result of lightning, the Churchill- Nelson Hydro electric development project construction has contributed as well.
Figure 5. This figure provides an easier comparison between the various dates of satellite images. The area around A was burned around 1985, it is still visible as pink in the 2000 image, and to winter image shows the area as white, indicating that the sparse tree cover has not reestablished itself.
