| Budget Amount *help |
¥2,000,000 (Direct Cost: ¥2,000,000)
Fiscal Year 1996: ¥700,000 (Direct Cost: ¥700,000)
Fiscal Year 1995: ¥1,300,000 (Direct Cost: ¥1,300,000)
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| Research Abstract |
The highest salt content in stem flow water was shown at measuring point 1 (sea side edge tree), showing of decreases in salt content at measuring point 2 (in the forest) and at measuring point 3 (land side edge tree) in this order. In making mutual comparison of the salt content of stem flow water at each measuring point and the salt content in rainwater, the salt content at measuring point 1 showed a remarkable high value, 2.8 times the value at measuring point 2,4.8 times the value at measuring point 3 and 40.0 times the value in rainwater. And the value at measuring point 2 showed 1.8 times the value at measuring point 3 and 14.6 times the value in rainwater. The value at measuring point 3 showed 8.3 times the value in rainwater. Consequently, it seems to us that the shorter the distance from coast is, the more salinity is caught by trees, and with the distance from coast, the amount of caught salinity decreases.
The vegetation on the strand and the rocky reef was surveyed on south
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coast of Itoman City located in the southern part of Okinawa Island and Aguni Island. The zonate difference was clearly observed from drift line to inland in the vegetation. On the strand vegetation there was growing Sporobolus hancei community -> Hibiscus tiliaceus- Pandanus odoratissimus community -> Casuarina equisetifolia forest in Itoman and Ipomoea pes-caprae ssp. brasiliensis community-> Cassytha filiflormis- Thuarea involuta community-> Argusia argentia- Crepidiastrum lanceolatuln f. pinnatilobum community -> Hibiscus tiIiaceus community -> Casuarina equisetifolia forest in Aguni Island. There was growing Zoysia matrella var. pacifica community -> Scaevola taccada community -> Pandanus odoratissimus community on the rocky reef vegetation in Itoman. The damage to plants from typhoon varied with the position at a distance from drift line and species.
Diseases of Coastal stands of Ryukyu pine (Pinus luchuensis) and mangroves were actually surveyed in Okinawa, Miyako and theYaeyama Islands. The pitch canker disease was found in all pine stands. Analysis on promoting factors of the pitch canker showed that typhoon does not directly promote epidemic of this disease. A newly-reported dieback of Kandelia candel were found in mangroves in Okinawa and the Yaeyamas. Cryphonectoria sp., Botryosphaeria sp., Pestalotiopsis sp. were isolated from the lesions, and the first two showed pathogenicity after inoculation. Dieback of Rhizophora stylosa was also found in the Yaeyamas, which main cause was still not clear.
Properties of mangrove forest as an Okinawan coastal prevention forest were examined. Several stand parameters were measured at 15 plots in Iriomote Island and Ishigaki Island. The maximum of mean tree height and diameter at breast height was 8.4m and 14.0cm, and the minimum was 1.9m and 3.6cm. 98.6% of the former plot was occupied by Bruguiera gymnorrhiza and 85.7% of the latter was occupied by Rhizophora stylosa. Stand density corresponded to the plots obtained the above values was 1,850 and 12,600 (1/ha). Significant high correlation was recognized among parameters of tree height, diameter at breast height, stem volume and crown area of each tree in a plot. And there was significant high correlation among stand parameters of each plots. Less
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