The time of first blooming and fruiting of birch varied greatly in different habitats and origins.On the same habitat,seed\|origin plant bloomed over 6 years later than that from sprouts.The first flowers in mesic site appeaired earlier than those in wet site.Blossom date within a year also varied among different stands.Catkin module number,reproductive branch number,and the number of catkins per reproductive branch were directly related to the age of tree.The number of catkin modules in middle\|aged trees>...