Synchronous NDVI and surface air temperature trends in Newfoundland: 1982 to 2003

Abstract

We investigated two unusual systematic normalized difference vegetation index (NDVI) growing season trends in Newfoundland from 1982 to 1999 within a satellite data record from 1982 to 2003 and attempted to determine their causes. We found direct correlations between increasing NDVI and increasing surface air temperature for the 1982–1990 and 1991–1999 growing seasons, punctuated by sharp simultaneous decreases in both surface temperature and the NDVI in 1991 from 1990 that were associated with the volcanic eruption of Mt. Pinatubo. No covarying trend between NDVI and surface air temperatures was found from 2000 to 2003. The responses of increasing plant growth, as indicated by the increasing NDVI, to increasing surface air temperature from 1982 to 1990 and 1991 to 1999, were also associated with a lengthening of the growing seasons of ∼9 and ∼17 days for these two periods, respectively. We found no systematic variations in precipitation, the presence of early season and late season snow cover, systematic variation in down‐welling photosynthetically‐active radiation, post‐forest fire succession, regrowth following logging of coniferous forests, and other land use changes that contributed to the 1982–1990 and 1991–1999 increasing NDVI trends. Our results document the influences of surface air temperature upon boreal forest plant growth and the cooling effects of major volcanic eruptions in this ecological system.