Radial growth response of understory sugar maple (Acer saccharum Marsh.) surrounding openings

Abstract Understory sugar maple around openings 15 to 75 m in diameter in mature hardwood stands gave a radial response over a 5-year period. Size of opening and distance into the uncut stand from opening edge, especially, affected the increase in diameter growth. The trend of response with distance ranged from a nearly 300% increase near the opening to 12% at 30 m into the stand, with opening sizes grouped, indicating that the openings affected growth more than 30 m into the stand. The interaction, opening size × distance, gave a strong relationship, significant at the 0.005% level because effect of opening size diminished as distance from opening increased. Sunlight intensity and available soil moisture were collected from three new openings, 15, 30, and 45 m in diameter and one new clearcut. Sunlight intensity dropped from about 33% along the opening edge to about 5% at 15 m into the stand. Percentage sunlight was directly related to percentage radial response (significant at 0.01% level) similar to the response relationship. However, no relationship were found for the interaction of available soil moisture with radial response as the moisture data ranged from 10 to 14% throughout the 30 m distance.