報告書番号

482004

タイトル（和文）

植林地内伐開と隣接の樹木生長との関係－北西斜面における樹令２２～２４年・ヒノキ単純林の場合－

タイトル（英文）

THE GROWTH OF TREES ADJACENT TO CUTTING-OVERAREA UNDER THE TRANSMISSION LINE -CASE OF THE PLANTATION OF 22-24 YEAROLD CYPRESS AT THE NORTHWEST FACING SLOPE-

概要 （図表や脚注は「報告書全文」に掲載しております）

送電線の通過により林内の一部が伐開された林令約２３年のヒノキ植林で，樹木調査を行い，以下の結果を得た。１）伐開前のヒノキの生長には斜面上の位置の違いによる差が存在した。２）伐開後のヒノキの生長は伐開地の隣接地が大きく，伐開地から離れるにしたがって小さくなった。３）伐開によってヒノキの生長が促進される範囲は伐開地より２０メートル位までの範囲であった。４）この範囲においては特に直径生長の促進が著しく，その結果樹形はずんぐりとした形状になる傾向にあった。

概要 （英文）

HEIGHT AND RADIAL GROWTH WERE COMPARED INSIDE A CYPRESS STAND WHERE THE CENTER ZONE WAS CUT-OVER BY PASS OF A NEW POWER TRANSMISSION LINE IN WESTERN JAPAN. SIX PLOTS AND ONE TRANSECT WERE PLACED ON UPWARD AND DOWNWARD SLOPE WITH DIFFERENT DISTANCE FROM THE CUT-OVER ZONE,AND CYPRESS TREES STANDING ON EACH PLOT OR TRANSECT WERE MEASURED FOR HEIGHT AND DBH IN APRIL 1978 WHEN CUT-OVER WAS DONE AND INNOVEMBER 1981. 1.THERE WERE DIFFERENCE FOR TREES IN AGEAND SIZE AMONG STUDY PLOTS. THE AVERAGED AGE OF TREE FOR PLOTS ON UPWARD SLOPE WAS 24 YEARS AND OLDER ABOUT 2 YEARS THAN THAT FOR PLOTS ON DOWNWARD OF THE CUT-OVER ZONE. MOVING DOWNHILL FROM THE UPPER PLOT TO THE LOWER PLOT,SIZEOF TREE DECREASED AND MAXIMAM DIFFERENCE AMONG PLOTS FOR HEIGHT OF TREE WAS ABOUT 60%. 2.THE GROWTH RATE OF TREES DURING 4 YEARS AFTER CUT OVER WAS 16 32% IN HEIGHT GROWTH,12 34% IN DIAMETER GROWTH,AND 47 157% INVOLUME GROWTH. EVERY GROWTH RATE WAS HIGHER AT BOTH NEAREST PLOTS TO THE CUT-OVER ZONE,AND DECREASED WITH INCREASING DISTANCE FROM THE CUT-OVER ZONE. 3.IT WAS ESTIMATED FROM THE REDUCTION OF THE GROWTH RATE WITH INCREASING DISTANCE FROM THE CUT-OVER ZONE THAT THE RANGE WHERE AN ACTION OF CUT-OVER SHOULD PROMOTE THE GROWTH RATE OF THE NEIGHBOURING TREESWAS ABOUT 20 M FROM THE CUT-OVER ZONE. 4.TREE RINGS MEASURED FROM THE INDIVIDUAL TREES AT DIFFERENT DISTANCE FROM THE CUT-OVER ZONE SHOWED THE SAME TIME-SERIES CHANGE PATTERN TO BECOME WIDEST IN 1972YEAR AND SINCE THEN TO REDUCE GRADUALLY WITH INCREASING YEAR. BUT COMPARISON OF THISPATTERN AMONG THE TREES GROUPS OF DIFFERENT DISTANCE BY LIMITING THE PERIODTO DURING 4 YEARS AFTER CUT OVER REVEALED THAT THE DEGREE OF THE REDUCTION WAS SMALLEST IN THE GROUP OF TREES WHICH WAS NEAREST TO THE CUT-OVER ZONE.

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