Friday, August 6, 2010

PS 96-67: Differential photosynthetic adaptation between size-classes of Spruce and Fir juveniles help to explain the co-existence of the two species

Edgard A. Bontempo e Silva, Toshihiko Hara, Akihiro Sumida, and Kyiomi Ono. Hokkaido University


Abies sachalinensis (Sakhalin Fir) and Picea glehnii (Glehn’s Spruce) are major components of the sub-boreal forests of Hokkaido, Japan. Similar Spruce-Fir forests can be found in many other places in the northern hemisphere and will probably be impacted by global warming. Therefore, detailed knowledge of these species’ physiology and life-history strategies at different growth stages is important to understand present communities and to support reliable prediction of possible consequences of global climate change.

Accordingly, the objective of this study was to establish relations between community dynamics, life-history strategies and photosynthetic adaptation of these species, on different developmental stages.

The study is taking place on a sub-boreal forest plot in north Japan (N 44º 19’, E 142º 15’). Twenty shade-growing individuals of both species were divided into two height classes: seedlings, if height < 50cm; and saplings, if height > 100cm. The canopy coverage over each individual was assessed by analyzing hemispherical photography and average light incidence. Leaf pigments are being analyzed by chromatography. Light response curves and chlorophyll fluorescence are being measured seasonally, except in winter. Results are analyzed through General Linear Models. The study started in spring 2009 and will continue until early-summer 2010.


Preliminary results show an inversion of the photosynthetic adaptation between seedlings and saplings, and also between species. Picea seedlings and Abies saplings have greater total chlorophyll content and higher photosynthetic rates than Picea saplings and Abies seedlings. As a consequence, the superior competitor between similar sized individuals of both species appears to change between size-classes, with Abies presenting higher photosynthetic rates at the sapling class and Picea at the seedling class. Nevertheless, no significant growth has been observed in any of the groups until now. Results also disagree with some of the previously reported photosynthetic characteristics of these species, with Picea seedlings displaying more traits usually associated with shade adaptation than Abies seedlings.