白桦的开花时间及生殖构件的数量与树龄和树冠层次的关系

白桦的初始开花结实年龄在不同生境、不同起源情况下是有很大差别的。在相同地生境下，实生苗比萌生苗的始花年龄晚６ａ以上，中生生境的林分始花期要早于湿生生境的林分，在同一年中花期的早晚因林龄而异。花序构件种群、生殖技构件种群以及生殖枝花序数量都与树龄直接相关。花序构件数量壮年期〉老龄期〉结实初期。在同一生殖个体上，构件数量雄花序为中层〉上层〉下层，雌花序数量为土层〉中层〉下层，每个生殖枝平均的花序构件数

The blooming and production of reproductive modules in relation to tree age and their position within crowns in Betula platyphylla

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>...