| Budget Amount *help |
¥1,900,000 (Direct Cost: ¥1,900,000)
Fiscal Year 1988: ¥500,000 (Direct Cost: ¥500,000)
Fiscal Year 1987: ¥1,400,000 (Direct Cost: ¥1,400,000)
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| Research Abstract |
This research was conducted on a representative tree within a 13-year-old plantation of hinoki (Chamaecyparis obtusa (S. et Z.) Endl.). The tree height, stem girth at 1.0 m aboveground, and stem volume were respectively 4.9 m, 19.1 cm, and 8.2 dm^3 as of June, 1988. The aboveground part of the forest-tree was enclosed with an assimilation chamber made of polyvinyl chloride films 0.2 mm thick (ca.90% transmissivity of photosynthetically active radiation). Temperature inside the chamber was synclonized with that outside the chamber by means of a temperature controller. CO_2 content in air at the inlet and outlet of the chamber was determined with an infrared gas analyzer. The amount of the air entering the chamber was 60 to 120 m^3 h^<-1> in the daytime, while 10 to 60 m^3 h^<-1> in the nighttime, as measured with a thermal flow meter. Radiation was measured above the crown using a photometric sensor.
The respiration rate RT (gCO<@D22@>D2 tree<@D1-1@>D1 h<@D1-1@>D1 of the aboveground part was exponentially related to the temperature T ( C) inside the chamber: R<@D2T@>D2 = R<@D20@>D2.exp(k.T), where R<@D20@>D2 and k are coefficients specific to each month. The Q<@D10@>D2 value ("exp(10.k)) for respiration was in the range from 2.5 to 3.0 during the winter season with the temperature variation of -1.5 to 10.5 C, while from 1.4 to 1.6 during the summer season with the temperature variation of 18 to 30 C. This fact shows that the Q<@D210@>D2 has high values in the winter season than in the summer season. The daily gross photosynthesis was assessed from adding the net gain to the daiuly respiration, which was calculated from considering the above equation of the R<@D2T@>D2 - T relation. The relationship between the daily gross photosynthesis P<@D2g@>D2 (gCO<@D22@>D2 tree<@D1-1@>D1 d<@D1-1@>D1) and the daily illuminance I (klx.h d<@D1-1@>D1) was formulated in the form: 1/Pg =A/2 + B, where A and B are coefficients specific to each month.
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