The effect of thinning on growth and wood production of Caucasian alder (Alnus subcordata) plantation in Nowshahr region

In order to study the effect of thinning operation on growth and wood production, an alder plantation (Alnus subcordata) on deep and moist soil with medium fertility was selected and thinned during 10 years. All standing and fallen trees were measured in terms of diameter at breast height (d.b.h), total height and standing volume. By thinning, the number of standing trees were decreased from 1700 to 400 stem per hectare. Results show that after thinning, the percentage of mortality decreased from 35% to less than 1% during 10 years. D.B.H growth, total height and standing volume increased 76%, 40% and 17%, respectively. The mean annual increment of standing volume was greater than 20 m3 for alder plantation grown on heavy and moist soil. Thus, Caucasian alder is proposed for intensive wood culture program in such areas (which are not suitable for poplars) in Caspian coastal plains