Abstract
We investigated the influence of thinning (thinning intensities were 20.5 and 38.5%) on the sheltereffect of inland windbreaks for protecting outdoor activities. Both thinnings were intended to improve the overcrowd-ed condition. The shelter effect was evaluated by the shelter distance at which the wind speed returned to the critical wind speed (which causes initial damage to the protected object) on the leeward side of the windbreak. Wind speeds before and after thinning were measured at a height of 1.5 m. As a result, the shelter effects after 20.5 and 38.5% thinning were evaluated to be the same as or slightly lower before than those thinning when the wind speed on the windward side was less than 2.9 m/s. When the wind speed on the windward side was over 2.9 m/s, the shelter effect covered about 70% of the park next to the windbreak. It was thus found that the shelter effect after thinning to preserve this windbreak was the same as or not much less than that before thinning.
