The effect of growing season and summer greenness on northern forests

We investigate the physiological effects of the elongation of the growing season and the increase in summer greenness on northern hemisphere forests by examining the relationship between NDVI and tree rings. These variables are correlated during June and July only. These results suggest that NDVI proxies the physiological status of trees and that the summer status of the canopy has a larger effect on tree vigor than the duration of the canopy.