Effect of gap size on the regeneration in plantation.

We conducted a survey on seedlings (height <1 m) and saplings (height ≥1 m, diameter at breast height <5 cm) in 20 gaps of plantations on Guandi Mountains, Shanxi to analyze regene-ration density, growth indicators, and spatial distribution of seedlings and saplings under four gap sizes (<60 m, 60-120 m, 120-180 m, and ≥180 m). The results showed that growth indicators (ground diameter, height) of seedlings and saplings and regeneration density of seedlings were highest in small gaps (14-60 m). The sapling regeneration density was highest in medium gaps (60-120 m), and sapling density exceeded seedling density in each size category. seedlings and saplings exhibited favorable regeneration in small and medium gaps, while large gaps (120-180 m) and extra-large gaps (≥180 m) were unfavorable for regeneration. seedlings and saplings were mainly distributed within the canopy projection area and along the edge of canopy gap area. Controlling gap size within the range of 14-120 m through artificial interventions, such as planting and thinning, could promote the regeneration of .