تاثیر سطح روزنه تاج پوشش بر نرخ فتوسنتز خالص و ویژگی‌های برگ نهال‌های راش در دو توده شاهد و مدیریت شده

Fagus orientalis is one of the most important species in the northern Iranian forests. Regeneration establishment is created by canopy opening resulted from the mortality of overstorey trees. The opening area has a significant effect on survival and growth of seedlings. The present research focused on determining optimum canopy opening area for natural Beech stands at Shastkola forest, also the effect of the opening areas on environmental factors, affecting on net photosynthesis rate and leaf characteristics. All stages of the research procedures have been replicated in both managed (by selection method) and natural (control) stands. The field categorization of canopy opening areas indicated that there were seven classes of canopy closure and also seven canopy opening areas ranging from 9 to 53 m2. Leaf growth characteristics and net photosynthesis rate were evaluated in each of the canopy opening areas by LCA3 and compared by variance analysis and Duncan test. Also the mean opening area per hectare was 1338 and 1957m2 per hectare for the control and managed sections, respectively. The results indicated that the mean opening area per hectare and opening area above each regeneration area of Beech stands were the major factors in controlling photosynthesis condition in such a way that seedlings establishment in the areas with smaller average opening area per hectare and larger opening area above the regeneration areas exhibit higher net photosynthesis rate per unit leaf area and also for the total net photosynthesis rate. The research also indicated that there was non-significant relationship between leaf area and opening areas in the control section but significant negative correlation in the managed section.