Tending methods for useful tree species invaded into unmanaged plantations and improving CO2 fixation capacity

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Photosynthetic characteristics of leaves of seedlings and trees of deciduous broadleaved forests were studied from a leaf to stand level to access canopy photosynthetic production in connection with satellite data. Photosynthetic traits of seven deciduous broad-leaved trees was detected with use of a canopy tower and showed specific pattern of each species. In ash and maple, maximum net photosynthetic rate at sunny midday in summer was detected at the second layr of a crown but not surface part of the crown. Surface part of a crown may act as shelter for avoiding strong light flux. Leaf senescence started from the inner part of the crown in alder and birch, but originated either in the outer or top portion of the canopy for ash, basswood and maple. Chlorophyll to nitrogen ratio in leaves increased with decreasing photon flux density, which was detected by portable machines. There is a clear positive correlation between chlorophyll content and photosynthetic rate in one species, however, not among species. Nitrogen concentration was positively correlated well with light saturated photosynthesis in a species. Photosynthetic capacity of tree seedlings regenerated in a gap or floor of forests with deciduous leaf habit changed drastically through the season. Moreover, year-to-year variation of the photosynthetic rate at ambient CO_2 concentration was markedly large. This variation may be due to the diffusion resistance in a leaf because it disappeared at saturated CO_2. Potential capacity of photosynthesis of deciduous broad-leaved trees can be estimated by a portable nitrogen detector in field, which may be monitored by satellite image by way of leaf nitrogen content.