Photosynthesis characteristics of Alnus cremastogyne of two stand age

Photosynthetic rate of growing season about the two stand age(3-year-old,8-year-old) of Alnus crematogyme were measured and analyzed.The results show that: 3-year-old Alnus,the adjacent two parts of an average diurnal variation showed a single peak,peak occurred at 12:00.8-year-old Alnus showed two peaks,peak at 10:00 and 16:00.The two Alnus's annual net photosynthetic rate of upper leaves was higher than the lower leaves;the 8-year-old Alnus's Pn values in seasons was much more bigger than 3-year-old ones,the order from large to small of both plantation Alnus's Pn values of each season affeced by orientations was: June April September October,Pn of 8-year-old Alnus in four directions was higher than that of 3-year-old Alnus.There was significant difference(p= 0.017) between the three factors including two stand ages,different part of the leaves,different seasons.There was significant interaction between stand age and season,while no significant interactions between the other two factors.