Relationships between the light intensity under the canopy and floor vegetation cover in Sugi (Cryptomeria japonica D. Don) plantations in Iwate Prefecture
國崎, 貴嗣 ,
蓮沼, 友紀子 ,
上石, 有吾 ,
KUNISAKI, Takashi ,
HASUNUMA, YukikoAGEISHI, Yugo
20 , 2015-06-01 , 岩手大学農学部附属寒冷フィールドサイエンス教育研究センター
The relationship between light intensity under the canopy and floor vegetation cover were investigated in unthinned young and overcrowded mature plantations of Sugi (Cryptomeria japonica D. Don) in Iwate Prefecture. In 2012, thinning with an intensity of 38% of stand tree density was carried out in an overcrowded mature plantation, in 2014, a total of 20quadrats were established in the young and mature plantations, and floor vegetation cover, height increment of saplings and the relative photon flux density (rPFD) 0.8m above the ground were studied. The abundance of floor vegetation cover was positively correlated with the rPFD and was ＞ 75% when the rPFD was higher than 12.5%. The mean height increment of saplings was estimated to be 19cm per year when the rPFD equaled 12.5%. A yield index based on a stand density diagram was 0.598 when the rPFD equaled 12.5%. Thinning with an intensity of 50% or more of stand tree density is probably needed to improve the light condition under the canopy and to maintain luxuriant ground vegetation in overcrowded plantations of Sugi.