1992 Fiscal Year Final Research Report Summary
Changes in pollen production rates in Sugi stands with increasing stand age and soil fertility.
| Project/Area Number |
02660162
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| Research Category |
Grant-in-Aid for General Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Research Field |
林学
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| Research Institution | Kyoto Prefectural University |
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Principal Investigator |
SAITO Hideki Kyoto Prefectural Univ.Agric.Prof., 農学部, 教授 (20026636)
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| Project Period (FY) |
1990 – 1992
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| Keywords | Air-borne pollen / Cryptomeria japonica / Male flowers / Pollen / Pollen disease / Rates of production / Reproductivity |
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| Research Abstract |
The current increase of air-borne pollen from Sugi (Cryptomeria japonica D.Don) forest plantations, which were expanded through the policy of expensive afforestation after World War II, has contributed to the spread of Sugi pollen disease since 1975. Therefore, we studied changes in pollen (male flower) production of Sugi stands with ageing. Production rates of male flowers in a stand were measured by the litter trap method. The study stands were 11 plantations ranging in age from 12 to 90 yr and having mutual site conditions, and a stand about 600 yr old in the ground of a Buddhist temple. In the productive year 1991, the relationship between the number of open male flowers in a stand and stand age showed a ceiling curve, indicating a constant upper limit for several hundred years after the age of 50 yr. No difference in flower number was recognized among stands over 40 yr old because of the variation among the stands. On the other hand, in the unproductive year 1992, the numbers of flowers decreased to about 1% of that in the previous productive year, and did not vary among stands. The above results also indicate that an increase of pollen dispersal per unit land area is improbable if the final cutting age of Sugi plantations is increased to as much as 120-150 yr. Many closed male flowers fell before opening. In the ancient stand about 600 yr old, most flowers that fell after December at the end of pollen formation had aborted pollen sacs. However, in the other stands less than 90 yr old, most flowers had sound pollen sacs and pollen grains. The fall in the former stand was due to physiological causes, and that in the latter, to physical forces such as strong wind and snow-fall in winter.
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