Leaf morphology and photosynthetic adjustments among deciduous broad-leaved trees within the vertical canopy profile
Takayoshi Koike (1, 2, 5), Mitsutoshi Kitao (2), Yutaka Maruyama (2), Shigeta Mori (2, 3) and Thomasi T. Lei (2, 4)
1. Hokkaido University Forests, Sapporo 060-0809, Japan / 2. Forestry and Forest Products Research Institute (FFPRI), Sapporo 062-8516, Japan / 3. FFPRI, Morioka 020-0123, Japan / 4. CSIRO Cotton Research Unit, Locked Bag 59, Narrabri, NSW 2390, Australia / 5. Author towhom correspondence should be addressed () / Received August 18, 2000
Summary
Photosynthetic acclimation of deciduous broad-leaved tree species was studied along a vertical gradient within the canopy
of a multi-species deciduous forest in northern Japan. We investigated variations in (1) local light regime and CO2 concentration ([CO2]), and (2) morphological (area, thickness and area per mass), biochemical (nitrogen and chlorophyll concentrations) and physiological
(light-saturated photosynthetic rate) attributes of leaves of seven major species on three occasions (June, August and October).
We studied early successional species, alder (Alnus hirsuta (Spach) Rupr.) and birch (Betula platyphylla var. japonica (Miq.) Hara); gap phase species, walnut (Juglans ailanthifolia Carrière) and ash (Fraxinus mandshurica var. japonica Rupr.); mid-successional species, basswood (Tilia japonica (Miq.) Simonk.) and elm (Ulmus davidiana var. japonica (Rehd.) Nakai); and the late-successional species, maple (Acer mono Bunge). All but maple initiated leaf unfolding from the lower part of the crown. The [CO2] within the vertical profile ranged from 320–350 ppm in the upper canopy to 405–560 ppm near the ground. The lowest and highest
ambient [CO2] occured during the day and during the night, respectively. This trend was observed consistently during the summer, but not
when trees were leafless. Chlorophyll concentration was positively related to maximum photosynthetic rate within, but not
among, species. Leaf senescence started from the inner part of the crown in alder and birch, but started either in the outer
or top portion of the canopy of ash, basswood and maple. Chlorophyll (Chl) to nitrogen ratio in leaves increased with decreasing
photon flux density. However, Chl b concentration in all species remained stable until the beginning of leaf senescence. Maximum
photosynthetic rates observed in sun leaves of early successional species, gap phase or mid-successional species, and late
successional species were 12.5–14.8 μmol m–2 s–1, 4.1–7.8 μmol m–2 s–1 and 3.1 μmol m–2 s–1, respectively.
