Increment changes of Caucasian alder (Alnus subcordata) in Hyrcanian section of National Botanical Garden, Iran during three decades

Since the establishment of Hyrcanian section of National Botanical Garden in 1972, most of natural Hyrcanian trees have been transferred and planted in this section and they are 30-40 years old now. Due to lack of researches on growth procedure and adaptation of planted species in garden, the increment changes of Caucasian alder (Alnus subcordata) as an important Hyrcanian species was studied. Thirty felled trees were randomly selected and disks from their stumps were prepared. The disks were dried and prepared then annual rings widths were measured in the four geographical aspects using Vernier Caliper. The results showed that the age and diameter of sample disks were 22-30 years and 30-47 cm, respectively. Mean current annual increment was 11.9 mm. Maximum current annual increments and basal area increments were occurred in 5th and 11th years, respectively. Furthermore, drought periods had decreased diameter growth. The growth trends of these samples were matched with silvicultural growth stages.