Verbyla, D. L. 2001.
A test of detecting spring leaf flush within the Alaskan
boreal forest using ERS-2 and Radarsat SAR data.
International Journal of Remote Sensing. 22:1159-1165.
Abstract. This study tests whether ERS-2 and Radarsat
Standard Beam SAR data could be used to detect spring green-up of broadleaf
forests on floodplains in interior Alaska. SAR data were acquired
for pre- and post- budburst dates during the spring of 1997,1998, and 1999.
The images were radiometrically calibrated to dB and then geometrically
co-registered to a color infrared Landsat TM image. Ten broadleaf
and ten conifer floodplain forest polygons were then delineated from the
Landsat TM image for the extent of each SAR image. The mean dB from
each broadleaf and conifer stand was computed from each SAR image to test
whether there was a consistent change in mean dB associated with spring
leaf-out of broadleaf trees. There was no evidence that the
1997 or 1998 ERS-2 dB SAR data were useful for detecting spring leaf flush.
The 1998 Radarsat broadleaf stands all increased in dB after budburst,
but this was attributed to an increase in surface moisture from rain, rather
than due to spring leaf flush. The 1999 RADARSAT stands all decreased
in SAR dB after budburst, while control conifer stands increased and decreased
in dB during the same time period. Confounding factors such as changing
surface moisture, and possibly freezing/thawing effects may mask any change
in ERS or RADARSAT SAR dB due to spring leaf flush.
Email: D.Verbyla@uaf.edu
Last updated: August 2001