Canadian Forest Service Publications
Forest recovery trends derived from Landsat time series for North American boreal forests. 2016. Pickell, P.D.; Hermosilla, T.; Frazier, R.; Coops, N.C.; Wulder, M.A. International Journal of Remote Sensing. Vol. 37, No. 1, pp. 138-149.
Available from: Pacific Forestry Centre
Catalog ID: 36522
CFS Availability: PDF (download)
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A critical component of landscape dynamics is the recovery of vegetation following disturbance. The objective of this research was to characterize the forest recovery trends associated with a range of spectral indicators and report their observed performance and identified limitations. Forest disturbances were mapped for a random sample of three major bioclimate zones of North American boreal forests. The mean number of years for forest to recover, defined as time required to for a pixel to attain 80% of the mean spectral value of the 2 years prior to disturbance, was estimated for each disturbed pixel. The majority of disturbed pixels recovered within the first 5 years regardless of the index ranging from approximately 78% with normalized burn ratio (NBR) to 95% with tasselled cap greenness (TCG) and after 10 years more than 93% of disturbed pixels had recovered. Recovery rates suggest that normalized differenced vegetation index (NDVI) and TCG saturate earlier than indices that emphasize longer wavelengths. Thus, indices such as NBR and the midinfrared spectral band offer increased capacity to characterize different levels of forest recovery. The mean length of time for spectral indices to recover to 80% of the pre-disturbance value for pixels disturbed 10 or more years ago was highest for NBR, 5.6 years, and lowest for TCG, 1.7 years. The mid-infrared spectral band had the greatest difference in recovered pixels among bioclimate zones 1 year after disturbance, ranging from approximately 42% of disturbed pixels for the cold andmesic bioclimate zone to 60% for the extremely cold and mesic bioclimate zone. The cold and mesic bioclimate zone had the longestmean years to recover ranging from 1.9 years for TCG to 4.2 years for NBR, while the cool temperate and dry bioclimate zone had the shortestmean years to recover ranging from 1.6 years for TCG to 2.9 years for NBR suggesting differences in pre-disturbance conditions or successional processes. The results highlight the need for caution when selecting and interpreting a spectral index for recovery characterization, as spectral indices, based upon the constituent wavelengths, are sensitive to different vegetation conditions and will provide a variable representation of structural conditions of forests.
Plain Language Summary
Due to free and open access to satellite data we now have better environmental monitoring products and science. An understanding of regeneration of forest vegetation and the linkage to remotely sensed spectral indices remains to be determined. The objective of this research was to characterize the recovery trends associated with a range of spectral indicators of forest recovery and report the performance and identified limitations observed with each indicator. The majority of disturbed pixels recovered within the first five years regardless of the index (ranging from 77.9% with Normalized Burn Ratio to 95.3% with Tasselled Cap Greenness) and after 10 years more than 93% of disturbed pixels had recovered.
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