Photosynthetica 2008, 46(1):151-155 | DOI: 10.1007/s11099-008-0025-9

Photosynthetic water use efficiency in tree crowns of Shorea beccariana and Dryobalanops aromatica in a tropical rain forest in Sarawak, East Malaysia

Y. Kitahashi¹, T. Ichie², Y. Maruyama³, T. Kenzo³, S. Kitaoka^1,3, S. Matsuki^1,4, L. Chong⁵, T. Nakashizuka⁶, T. Koike^2,*

¹ Graduate School of Agriculture, Hokkaido University, Sapporo, Japan

² Hokkaido University Forests, Sapporo, Japan

³ Forestry & Forest Products Research Institute, Sapporo, Japan

⁴ Forest Research Institute of Sarawak, Kuching, Sarawak, Malaysia

⁵ Faculty of Agriculture, Iwate University, Morioka, Japan

⁶ Institute of Humanity and Nature, Kyoto, Japan

Photosynthetic water use efficiency (PWUE), stomatal conductance (g _s), and water potential were measured at two different positions in the tree crown of two emergent tropical tree species (Shorea beccariana Burck, Dryobalanops aromatica Gaertn. f.). The trees were about 50 m high, in a tropical rain forest in Sarawak, East Malaysia. In both species, g _s at the upper crown position at midday was lower than at the lower crown position, even though both positions were exposed to full sunlight; the difference was greater in S. beccariana. Hydraulic limitation occurs in the upper crown position in both species. A midday depression was observed in the photon saturated photosynthetic rate in both species, especially at the upper crown. However, PWUE was markedly higher in the upper crown than the lower crown at midday, even though no morphological adjustment was observed in the leaves; this difference was greater in S. beccariana.

Keywords: Dipterocarpaceae species; hydraulic limitation; leaf area and thickness; nitrogen; saturation irradiance; specific leaf area; stomatal conductance; water potential

Received: October 31, 2005; Accepted: August 24, 2007; Published: March 1, 2008Show citation