جستجوی مقالات مرتبط با کلیدواژه « دانگ تجدیدحیات » در نشریات گروه « کشاورزی »

The effect of management was studied on the variation of some crucial forest stand features in the district nine of Shafaroud Gilan during a 20-year period. The survey was conducted in the regeneration affectation on 1985 and 2007. The measurement were done with a similar design (systematic randomized sampling in a 150×200m grid and 0.1 ha circular field plots) in 1985 and 2007, respectively. A set of qualitative/qualitative factors were measured including the species type, DBH, height of two control trees, regeneration and tree qualitative condition in each plot. The results showed a significant difference (in 1% level) between DBH of mean basal area, basal area ha-1, number of trees ha-1, standing volume ha-1, Lorey height, regeneration rate ha-1 and qualitative degree in two surveys. Standing volume ha-1 decreased amongst the entire species, showing an increase in Alnus subcordata and a decline in Fagus orientalis portion. Besides, regeneration decreased in Fagus and Alnus, while the rate increased in common maple and hornbeam, respectively. In terms of qualitative features, the results showed an increase in 2, 3 and 4-grade trees, whereas the portion of 1 grade trees declined. It was thus concluded that the predefined goals of shelterwood system have not been reached to the 20-year period due to the problems existing within the regeneration affectation. Based on our conclusion, it is tough to meet the primary objectives of the regeneration affectation in the end of the period. The fact that the structure of Iranian north forests are uneven aged, it seems that our efforts would not be useful in order to convert the uneven aged forests stand to even aged forests stand. Even after two cuttings regarding shelterwood method, we can gradually transform the shelterwood method to selective method.