スギ巣植林の成長(III) : 30年生林分の成長

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植栽後30年経過したスギ巣植林についてその成長が調べられた．巣間隔が広く，巣間に空間があるA，C区と巣間隔が狭く，すでに完全に巣間の空間がうっ閉されているB区とでは生存率，個体成長にかなりの違いが生じていることが明らかになった．生存率については巣本数間でかなりの差がみられ，被圧され枯れる個体が多くなっていた．とくに6本植えの枯損がめだった．巣閣隔の狭いB区からは完全な6本巣は消滅していた．胸高断面積でみた平均個体の成長は巣本数が多いほど小さく，小本数の巣との差は増大する傾向にあった．巣内最大個体は本数の多い巣ほど小さい傾向がみられた．前回の調査ではA，C区で巣断面積合計に頭打ちの傾向がみられたが，今回の調査ではB区でもその傾向が見られた．巣本数密度が多いほど巣内に於ける順位1位木と最下位木との差が拡大しているが，順位1位木と2位木の差は比較的小さかった．最大木の順位はこの17年間60％以上の巣で不変であった．A 30-year-old sugi stand planted in clumps was surveyed. Because of the wide clump spacing, the crown closure by tree crowns of plots A and C was incomplete. However, plot-B with narrow spacing was completely closed. There were large differences in survival rate and individual growth between plot B and other plots. A large number of trees died due to oppression by adjacent trees and difference in survival rates increased between the clumps. A particular large number of trees had died in clumps of six trees. The entire clump of six trees disappeared from plot B due to narrow clump spacing. The greater the number of trees per clump, the smaller the individual mean basal area became, and the difference of individual mean between great clumps and small clumps showed a tendency to increase. The greater the number of trees per clump, the smaller the largest tree in the clump became. In the previous survey, even if the number of trees per clump increased, the basal area per clump showed a tendency to reach a ceiling in plots A and C. In this survey, this tendency was also observed in plot B. The greater the number of trees per clump, the greater the difference between the maximum and minimum trees in clump became, but the difference between the maximum and second trees was relatively small. The rank of maximum trees were fixed in over 60 percent of clumps over the 17 year period.
九州大学の論文

スギ巣植林の成長(III) : 30年生林分の成長

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