報告書番号

U93017

タイトル（和文）

スギの衰退と大気二次汚染物質との関係

タイトル（英文）

DECLINE OF JAPANESE CEDARS(CNYPTOMERIA JAPONICA D.DON)AND SECONDARY AIR POLLUTANTS

概要 （図表や脚注は「報告書全文」に掲載しております）

酸性降下物の影響が指摘されているスギの衰退現象を解明する一環として，おもに野外生態の観点から衰退の諸特徴を明らかにし，スギの衰退に関与している要因について検討した。スギの衰退は関東甲信地方，関西瀬戸内地方などで認められたが，仙台平野，宮崎平野などでは，健全に生育していた。これらスギの衰退地域において衰退木の形態的特徴，衰退木の発生状況，衰退林の地理的・地形的分布など衰退の諸特徴やスギの樹幹流・スギ林土壌の化学性などについて種々検討した結果，乾性の大気二次汚染物質の分布やそれに伴う諸特徴がよく一致し，スギの衰退には大気二次汚染物質が関与し，その影響の発現には降雨条件が間接的に作用している可能性が高いと考えられた。

概要 （英文）

THE RELATION SHIP BETWEEN SECONDARY AIR POLLUTANTS AND THE DECLINE OF JAPANESE CEDERS IS DISCUSSED ON THE BASIS OF VARIOUS SYMPTOMS AND CHARACTERISTICS OF DAMAGED TREES AND STANDS NATIONWIDE. SYMPTOMS OF DAMAGE ARE DISCOLOURATION OF 3 AND 4-YEAR-OLD NEEDLES,UNNATURAL DEFOLIATION AND SLOW DIEBACK.THE SYMPTOMS ARE OBSERVED IN BIG TREES,PARTICULALY ISOLATED FEES AND TREES PROJECTING FROM THE FOREST CANOPY.SEVERE DAMAGE IS OBSERVED IN THE KANTO-KOSHIN AND KANSAI-SETOUCHI DISTRICTS.THE DISTRIBUTION OF DAMAGED STANDS ROUGHLY COINCIDES WITH THE REGIONS OF HIGHLEVEL SECONDARY AIR POLLUTANTS IN THE WARM PERIOD FROM MAY TO SEPTEMBER.HOWEVER,DE SPITE HIGH-LEVEL SECONDARY AIR POLLUTANTS,THE DAMAGE IS LESS PRONOUNCED IN AREAS WITH PRECIPITATION OF MORE THAN800 MM IN THE WARM PERIOD.MEANWHILE,IN AREAS WITH LOW-LEVEL SECONDARY AIR POLLUTANTS,THE TREES ARE HEALTHY REGARDLESS OF PRECIPITATION LEVELS.A COMBINATION OF HIGH-LEVEL SECONDARY AIR POLLUTANTS AND LOW PRECIPITATION DURING THE CEDER GROWING SEASON IS A MAJOR FACTOR CONTRIBUTING TO DAMAGE.CHEMICAL ANALYSIS OF THE STEM FLOW OF THE TREES AND SOIL UNDER THE TREES SUGGESTS THAT:(1)DAMAGE TO CEDER TREES RESULTS FROM EXPOSURE TO DRY DEPOSITIONS;(2)SECONDARY AIR POLLUTANTS TRAPPED IN THE TREE CANOPIES ARE WASHED INTO THE SOIL BY STEM FLOW AND THROUGHFALL;AND (3)SOIL CHEMICAL PROPERTIES ARE NOT CONTRIBUTING TO CEDER DECLINE.

報告者

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