بررسي تغييرات مشخصه هاي كمي و كيفي توده هاي جنگلي بعد از يك دوره جنگلداري (مطالعه موردي: سري جنبه سرا- گيلان)

Evaluation of quantitative and qualitative forest stands changes during a Period of forest management Plan (case study: Janbe sara district-Guilan)

In order to investigate the qualitative and quantitative changes in forest stands of Janbe Sara district, some raw data collected in 1993 and 2003 were compared. Inventory in both years was carried out using systematic random sampling with network dimensions of 150x200 meter and 0.1 ha sample plot. In each sample plot, such factors as type of species, diameter at breast height in cm, height of two trees in each plot in meter, regeneration conditions and qualitative class of trees were measured. The results of comparison between 1993 and 2003 data show significant difference between mean of regenerationʹs density, stand density, average diameter of basal area and Lorey height in this period. Standing volume per hectare was significantly reduced about 19.63 silve/ha in 1993 comparing to 2003 (p-value < 0.05). Based on results, the average diameter of basal area was reduced from 42.638 in 1993 to 37.64 in 2003. Also average Lorey height had 2.42 meters of reduction and there were significant differences (p-value < 0.05) between average diameter of basal area and Lorey height in 1993 and 2003. The number of regeneration per hectare regarding to all species including Fagus orientalis, Tilia begonifolia, Carpimts betulus, Acer velutinum, Alnus sp., Fraxinus excelsior and other species increased during the period. But, percentage of first class trees in 2003 has been reduced. Also the percentage of second, third and fourth class trees increased in 2003 and these changes are significant.