Evaluation of spacing impact on quantitative and qualitative characteristics of Alder (Alnus subcordata C. A. Meyer) plantation

Current research was conducted for evaluation of spacing impact on quantitative and qualitative characteristics of alder (Alnus subcordata C. A. Meyer) in fifteen years period (1999-2004) by Randomized Completely Block Design with 5 treatments based on spacing in three replications at Ladjim forest region. Spacing trial treatments included 1×1, 1×2, 2×2, 2×3 and 3×3 meter. Results indicated that mean dbh was significantly different in spacing treatments. Hence, dbh and height for spacing 1 m × 1 m and 1 m × 2 m were minimum, while in spacing 3 m × 3 m were maximum. The results showed that decreasing in spacing causes increasing in slenderness coefficient. Also the slenderness coefficient significantly varied with age and spacing of alder stands. Overall, in current study till fifteen years experiment of spacing trials, we are able to conclude that spacing 2 m × 3 m is suitable for reforestation in north of Iran based on maximum amounts of dbh, annual diameter increment, mean total height, annual height increment, and optimum slenderness coefficient.