2022 Volume 104 Issue 3 Pages 154-161
Although line-thinning is recommended for coastal forest, no study has examined the effects of line-thinning on a densely planted coastal forest. To examine the effect of the first line-thinning, we established line- and zigzag-thinning plots and un-thinned plots in a coastal Larix gmelinii var. japonica stand in Hokkaido, in 2014. During line-thinning, one line was thinned and two lines were preserved. We measured the diameter at breast height and tree height of living trees in the plots in 2014 just before thinning, and in 2017 and 2020. Hemispherical photographs were taken in 2015 and 2020 to evaluate canopy gap closure. Wind speed was measured in the gap in two thinned plots and under the canopy in the control plot. The thinning effects of line- and zigzag-thinning were the same for improved diameter growth. Although the canopy remained open in the line-thinning plots after 6 years, a thinning effect was observed only for the first 3 years. No strong winds were observed in the gaps in either line- or zigzag-thinning plots. These results imply that more trees should be removed if we expect a persistent thinning effect. However, there is no concern about wind damage when thinning a young coastal stand.