A comparison of GPP by two forests stands Fagus crenata and Alnus japonica

*Tomoyo Nakano, Kohsuke Moriyama, Tatsuya Toda, Kohei Koyama, and Kihachiro Kikuzawa (Ishikawa Prefectural University)

Leaf longevity and lifetime carbon gain by a single leaf of two contrasting leafing deciduous-tree species, Fagus crenata and Alnus japonica were compared. Gross primary production (GPP) of Fagus and Alnus was estimated.

We marked some shoots and counted the number of leaves on the Fagus and Alnus from April to November 2008.We also marked some leaves and measured photosynthetic rates (Amax) under sufficient light(1500μmol m-2s-1) at one-or two-week intervals. We also made light-response curves of photosynthesis of these leaves several times (around one-month interval within a season).We set light sensors, and measured PPFD. By using these values, we estimated lifetime photosynthetic gains by single leaves.

Although mean leaf longevity of Alnus (around 86 days) was shorter than mean leaf longevity of Fagus (around 177 days), lifetime carbon gain of Alnus by a single leaf was greater than that of Fagus.

Using these values, we calculated gross primary production values of these forest stands.