Health assessments of riparian forests using the Landsat archive

Abstract

The archive of satellite imagery from the Landsat Program between 1984 and 2020 was leveraged to assess the health status of riparian cottonwood forests along the regulated Oldman River in semi-arid southern Alberta, Canada. An extension of the near-infrared reflectance of vegetation, NIRvP, was adopted as a health indicator and validated to be a practical yet meaningful proxy of primary production. NIRvP was correlated with streamflow and a climatic soil moisture index from year-to-year. Forests responded to reduced streamflow with curtailed productivity, but were vigorous with return of adequate moisture. Forests did not respond to low flow characteristics, including reoccurring dewatering during the mid--late summer in years prior to the Oldman River Dam. These results supported that cottonwoods avoided, resisted, and were resilient to relatively short drought-like conditions imposed by streamflow reductions. Under current conditions, the outlook on the health of the riparian corridor is positive.