Centripetal Fall Colors

December 04, 2011


ChinesetreeIMG_3221 (2)

: Bruce Gervais 
Summary Author: Bruce Gervais

This handsome Chinese pistache (Pistacia chinensis) put on a nice display of fall colors in late November of 2011 after a cold snap at mid month. Fall colors and subsequent leaf abscission are triggered both by photoperiodism (changing day length) and by decreasing nighttime temperatures. The Chinese pistache featured here is showing centripetal fall color maturation -- the onset of fall coloration occurs from the top down. During the longer nights of autumn, emitted longwave radiation cools the upper tree canopy, but the leafy canopy hinders radiational cooling near the base of the tree. This results in delayed onset of fall colors closer to the ground. The surrounding buildings on this college campus enhance this effect by decreasing airflow and thermal mixing. So, by the time the leaves at the base turn color, the topmost leaves will begin abscising. Photo taken on November 22, 2011.

Photo details: Camera Maker: Canon; Camera Model: Canon PowerShot SD1300 IS; Focal Length: 8.022mm; Aperture: f/3.5; Exposure Time: 0.013 s (1/80); ISO equiv: 80; Exposure Bias: none; Metering Mode: Matrix; White Balance: Auto; Flash Fired: No (enforced); Orientation: Normal; Color Space: sRGB; Software: Microsoft Windows Photo Viewer 6.1.