Difference in Suppression Effect on Sugi Planted Trees between Miscanthus- and Deciduous-Tree-Dominated Vegetation

Abstract

This study clarified the suppression effects of Miscanthus (Miscanthus sinensis) - and deciduous-tree-dominated vegetation on sugi (Cryptomeria japonica) planted trees with reference to two aspects; limitation of light for photosynthesis and inhibition of crown development. The growth of sugi saplings during the three years after planting and branch volume of sugi in the fourth year were investigated in Miscanthus-dominated vegetation (Miscanthus type: M) and deciduous-broadleaved-dominated vegetation (deciduous broadleaved type: DB). The analyses using generalized linear mixed model demonstrated that the growth of sugi saplings under competitive status where the crown top was not suppressed was significantly lower in M compared to that in DB. The branch volume of sugi saplings at the 61-100 cm in height was also lower in M than in DB. These results suggested that the dense foliage of Miscanthus covering the large part of branches in lower crown of sugi limited light more severely than deciduous trees and/or shrubs. These results also suggested that the contact of Miscanthus foliage might have inhibit the development of sugi crown more strongly than deciduous trees and/or shrubs. We concluded that these suppression effects in M caused a more pronounced reduction in the growth of sugi saplings than DB, suggesting a need of taking into account the suppression on the lower crown and the inhibition of branch development when we consider to reduce the weeding frequency or period in the young plantation site dominated by Miscanthus.