Annual and seasonal variations in photosynthetic capacity of Fagus crenata along an elevation gradient in the Naeba Mountains, Japan
Quan Wang (1, 2), Atsuhiro Iio (1), John Tenhunen (3) and Yoshitaka Kakubari (1)
1. Institute of Silviculture, Shizuoka University, Shizuoka 422-8529, Japan / 2. Corresponding author () / 3. Department of Plant Ecology, University of Bayreuth, Bayreuth D-95440, Germany / Received May 6, 2007; accepted July 9, 2007; published online December 3, 2007
Summary
Canopy photosynthetic capacity, measured as leaf maximum carboxylation rate (Vcmax), is a key factor in ecosystem gas exchange models applied at different scales. We report seasonal and interannual variations
in Vcmax of natural beech stands (Fagus crenata Blume) along an altitudinal gradient in the temperate climate zone of Japan. Estimates are based on 6 years of gas exchange
measurements. Pronounced seasonal and interannual variations in Vcmax normalized to 25 °C (Vc,25) were found for sun leaves. The seasonal pattern of Vc,25 generally followed an inverse parabolic curve, with an increase in spring, peak values in the middle of the growth period
and a decline in autumn.
Leaf nitrogen concentration (Nl) and leaf mass per area were significantly related to Vc,25 during spring and summer, but were unrelated in autumn when Vc,25 declined. Annual peak Vc,25 ranged from 40.1 to 97.0 µmol m–2 s–1 and varied over as much as a twofold range at a particular site. Annual peak Vc,25 occurred about 28 days before annual peak Nl, with which it was poorly related. Our results show that it can be inappropriate to include constant values of photosynthetic
parameters in ecosystem gas exchange models.
