Ecophysiological Study on Maintenance Mechanism of Boreal Coniferous Forests on Coastal Dunes and Evaluation on Conservant Function of Front Dune

本研究旨在探讨冷杉天然林在海岸沙丘上的维持机制，并评价北海道北部若坂奈海岸森林前沙丘线的保护功能。研究了冷杉再生的空间格局、树木形态与海岸风的关系、沙丘土壤性质、冷杉的生理特征、树冠结构及其对光的利用、树木年轮分析、地上生物量和崩塌模型。冷杉林分密度在26年龄为16万株/ha， 77年以上为600株/ha。冷杉林的更新面积为1000 ~ 4000 m^2，滨海冷杉林面积大于内陆冷杉林面积。森林的崩塌是从海岸开始的。夏季盛行南风（陆风），冬季盛行北风（海风）。冬季平均风速比夏季大。冬天的强风使一群人向下风方向聚集。前沙丘线的切断造成了森林的崩塌和土壤的高氯离子。树木年轮分析表明，前沙丘的砍伐影响了森林的生长和崩塌。冷杉4年以下叶质量占总叶质量的70 ~ 100%。树高限制为12米，80年左右开始倒塌。很明显，前面的沙丘线保护着冷杉林。

The purpose of this study is to investigate the maintenance mechanism of Abies sachlinensis natural forests on coastal dunes and to evaluate the conservant function of a front dune line at Wakasakanai coastal forests, northern part of Hokkaido. The spatial patterns of regeneration, the relationship between tree shapes and coastal wind, the soil properties of dunes, the physiological characteristics of Abies, the crown structures and their utilization of light, tree ring analysis, above-ground biomass and a collapse model were investigated. The stand density of Abies is 160,000/ha in 26-years-old to 600/ha in over 77-years-old. A regeneration area of Abies forests is 1,000〜4,0O0m^2 and the size on coast side is larger than that on inland side. Collapse of forests had begun from coast side. South to east wind (land wind) prevails in summer and north to west wind (sea wind) in winter. Average wind velocity is stronger in winter than in summer. Strong wind during winter caused a clustered to leeward. Cut of the front dune line has caused the collapse of forest and high chloric ion of soil. Tree ring analysis showed that the cut of front dune had affected on the growth and collapse of forests. Leaf mass less than 4-years-old of Abies is 70〜100% of all leaf mass. Limit of tree height is 12 m and collapse will start around 80 years. It is clear that a front dune line protects Abies forest.