Canopy photosynthetic production in a Japanese larch stand. I. Seasonal and vertical changes of leaf characteristics along the light gradient in a canopy |
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Authors: | Nahoko Kurachi Akio Hagihara Kazuo Hozumi |
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Institution: | (1) Laboratory of Silviculture, Faculty of Agriculture, Nagoya University, 464-01 Nagoya, Japan;(2) Present address: Forestry and Forest Products Research Institute, 305 Tsukuba, Ibaraki, Japan;(3) Present address: Hattori 2-13-5 Ikaruga-cho Ikoma-gun, 636-01 Nara, Japan |
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Abstract: | In an 18 year old Japanese larch stand, leaf characteristics such as area, weight, gross photosynthetic rate and respiration
rate were studied in order to obtain basic information on estimating canopy photosynthesis and respiration. The leaf growth
courses in area and weight from bud opening were approximated by simple logistic curves. The growth coefficient for the area
growth curve was 0.155–0.175 day−1, while that for the weight growth was 0.112–0.117 day−1. The larger growth coefficient in area growth caused the seasonal change in specific leaf area (SLA) that increased after bud opening to its peak early in May at almost 300 cm2 g−1 and then decreased until it leveled off at about 140 cm2g−1. The change inSLA indicates the possibility that leaf area growth precedes leaf thickness growth. The relationship between the coefficientsa andb of the gross photosynthetic rate (p)-light flux density (1) curve (p=bI/(1+aI)) and the mean relative light flux density (I′/I
0) at each canopy height were approximated by hyperbolic formulae:a=A/(I′/I
0)+B andb=C/(I′/I
0)+D. Leaf respiration rate was also increased with increasingI′/I
0. Seasonal change of gross photosynthetic rate and leaf respiration rate were related to mean air temperature through linear
regression on semilogarithmic co-ordinates. |
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Keywords: | gross photosynthetic rate Japanese larch leaf growth leaf respiration rate |
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