Vegetation Recovery Since Establishment of Spur Roads for Thinning in Coniferous Plantations

27 Mar Vegetation Recovery Since Establishment of Spur Roads for Thinning in Coniferous Plantations

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Abstract

間伐後1～7年経過した複数のスギ人工林で，作業道の植生回復を調査した。GLMによる解析の結果，ほとんどのモデルにおいて種数または植被率に対して作業道を開設してからの年数が要因として選択された。しかしながら，枝条散布の有無は選択されなかった。平均種数は，開設後3年目で12.4種/m2 となり，5～7年は10.9種/m2であった。平均植被率は，3年で58%となり，5～7年で86%となった。草本の種数と植被率は，開設後3年目まで増加しそれ以降減少したのに対し，木本は5年まで増加しそれ以降横這いとなった。一方，チマキザサの植被率は年数にともなって増加する傾向がみられた。これらの結果から，作業道での植生回復は，開設後3～5年に草本から木本やササへの優占変化をともないながら枝条散布とは関わりなく増加し，路面の安定化に寄与しているものと考えられる。

English Abstract

We investigated the recovery of vegetation on the spur road established in several Cryptomeria japonica plantations from one to seven years after thinning. From GLM a lysis, the year after establishment was considered the primary factor for the recovery of vegetation in most models. The scattering of branches had no effect. The mean number of species at the third year after establishment was 12.4 per m2 and it was 10.9 per m2 at the fifth to seventh year. The mean vegetation coverage was 58％ at the third year and 86％ at the fifth to seventh year. The number of species and vegetative coverage of herbaceous plants increased until the third year and decreased thereafter whereas these of woody plants increased by the fifth year and did not change thereafter. Meanwhile, vegetative coverage of Sasa palmate increased with the year. From these results, vegetation recovery of the spur road is considered to increase irrespective of the scattering of branches with a change of domi nce from herbaceous to woody plants or bamboo grass at the third to fifth year after the establishment, and to contribute to the stabilization of road surface.