A photosynthesis model was developed to estimate the seasonal variation of needle photosynthesis (
Pn) of
Larix kaempferi in this study. On the basis of the physiological factors, the seasonal variation of photosynthesis was estimated from the leaf nitrogen content (N). Additionally, the effect of vapor pressure deficit (VPD) on photosynthesis was considered as the environmental factor. A positive correlation between
Pn and N was found. However, there was a decrement in
Pn under high VPD even though N was at the same level. Consequently, the photosynthesis-nitrogen relationships were developed by dividing VPD into two ranges: 0 < VPD < 2 and VPD ? 2. Finally,
Pn was estimated from the photosynthesis-nitrogen relationships. The estimated
Pn was fairly closed to the observed
Pn throughout a year and represented a temporary decline which occurred frequently in summer induced by the water stress.
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