تاثير حذف درختان اشكوب فوقاني روي برخي ويژگي هاي كمي و كيفي درخت شمشاد

Influence of elimination of upperstorey trees on some quantitative and qualitative characteristics of Buxus hyrcana (in Si-Sangan Forest Reserve)

Response of some quantitative and qualitative characteristics of Buxus hyrcana to elimination of upperstorey trees was investigated in Si-Sangan Forest Reserve (north of Iran). For this purpose, three Buxus thicket groups (treatments) of lacking upperstorey occurring at relatively circular gap sizes of 100-200, 300-400 and 1000-1200 rrr, as well as one Buxus thicket group under upperstorey (control) were selected at three replications. Stem quality, stem forking, crown vitality and diameter increment of Buxus thickets (with d.b.h. > 7 cm) were reordered at center of 100 m^ circular plots. The results revealed that stem quality was not affected by gap size; however, frequency of first-grade stem quality was greater under complete crown canopy (control) and 100-200 m^ gap size. In contrast, frequency of first-grade vitality, as well as two-branched trunks, was greater in 1000-1200 m^ gap than in other gap treatments. Recent 20-year d.b.h. increment appeared in complete crown canopy was thinner than those in other treatments. Generally, it could be deduced that with elimination of upperstorey, some qualitative or quantitative characteristics of B. hyrcana thickets were declined and some others were improved, it can be also stated that Vitality does not decline when created full light woth removal of upperstorey.