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

Edgard Bontempo E Silva,Akihiro Sumida,Toshihiko Hara,Kiyomi Ono

doi:10.1038/npre.2010.5298.1

Abstract

Abstract Background/Question/Methods _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 period was from spring 2009 to summer 2010. Results/Conclusions 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.

Highlights

Spruce and Fir dominate many of the boreal and alpine forests of the world
The study site was a hardwood-mixed forest located at the Uryu Experimental Forest of Hokkaido University (N 44o 19’, E 142o 15’)
Size classes were found to be homogeneous (p

Summary

Introduction

Spruce and Fir dominate many of the boreal and alpine forests of the world These forests hold more than 25% percent of the carbon stored in terrestrial ecosystems and are likely to be affected by global climate change (Easterling et al, 2007). Abies and Picea populations have received considerable attention in Japan (e.g., Kubota et al, 1995; Takahashi, 1997) and it has been recently proposed that reversals in competitive superiority at different life stages could play an important role in the coexistence and co-dominance of these species (Nishimura et al, 2009). In this work, we attempted to analyze juvenile trees of Abies sachalinensis (Sakhalin Fir) and Picea Glehnii (Sakhalin Spruce) from an ecophysiological perspective, testing for differences between seedlings and saplings of both species, aiming to provide mechanistic background to explain the observed patterns of their coexistence in the sub-boreal forests of Hokkaido

Methods

Results

Conclusion