Long-term impact of selection cutting management on frequency of stem deformity in mixed beech forests, northern iran

Abstract

The aim of this study was to evaluate the long-term effect of selection cutting management on the stem quality of remaining trees in forest. For this purpose, three parcels managed for three decades by selection cutting as managed stand (MP), and two protected parcels without tree felling were selected as control stands (PP). First, the frequency of deformed stems in each parcel was determined through circular 1000 m2 area of each plot by systematic sampling of 100 m × 100 m grid dimensions, then stem deformity index was estimated for each of the deformed stems. Results showed that the frequency of stem deformity in the MP (6.5%) was significantly lower than the PP (20.7%) (p <0.01). In addition, frequency of all types of stem deformities in the MP was significantly lower than the PP. Furthermore, selection cutting management reduced the indices of twisting, decaying, conicity, forking, and ellipticity by 58.4, 53.9, 34.7, 8.4 and 6.8%, respectively. The results of the correlation between frequency of stem deformity and diameter at breast height (dbh) of trees showed that the curves follow a parabolic shape in both the MP (r = 0.83) and PP (r = 0.80), which the frequency of deformed stems reduced with increasing tree dbh (up to 75 cm in MP, and up to 65 cm in PP), and then it increases with greater dbh. Selection cutting management, regardless of tree species, improved the stem form. Decaying accounted for a high proportion (24.1%) of the total deformity in the MP, mainly due to logging damage. Overall, the results of this study showed that selective management has been successful in improving the quality of tree boles in the studied mixed beech stands. Regular and long-term stand monitoring and statistical quality control (SQC) can be a good approach to aligning ecological and economic goals in forest management.