水分条件对白桦天然林生长影响的研究

针对全球变暖导致的降水格局变化，选择生长于不同水分条件（湿生立地和中生立地）的中龄天然白桦林为研究对象，研究其生长状况并分析其生长过程。结果表明，水分条件对白桦天然林的密度和平均胸径具有显著影响（p=0.043 3和0.007 9），中生立地条件下白桦天然林的密度低于湿生立地（降低46.8%），而平均胸径则前者高于后者（增加52.4%）。中生立地白桦天然林的胸径分布为正态分布（p=0.823 9），而湿生立地白桦胸径分布呈明显的左偏（p=0.000 8）。水分条件能影响实生天然白桦胸径、树高生长过程，而对材积生长过程影响不大。湿生立地白桦的胸径速生期持续时间长于中生立地，前者速生期在6~15 a，后者在9~12 a，中生立地白桦胸径的数量成熟龄晚于湿生立地1~2 a；湿生和中生立地白桦高生长的速生期均在6 a，中生立地白桦树高的数量成熟龄晚于湿生立地3~6 a；湿生和中生立地白桦材积的速生期均在24 a以后，湿生和中生立地白桦材积的数量成熟龄均为24 a以后。

Comparison of Growing Progress of Betula platyphylla in Different Natural Habitats

The growth of natural birch(Betula platyphylla) in different habitats (wet and moderate-water habitats) was studied. The results showed that the density and DBH of natural birch in different habitats were significantly affected by soil water. The density of birch forest in moderate-water habitat was lower than that growing in wet habitat, decreased by 46.8%. The DBH of birch in wet habitat was higher than that growing in moderate-water habitat, increased by 52.4%. The DBH distributions of birch in moderate-water and wet habitats were normal and left-skewed distributions, respectively. The DBH and height growing processes were impacted by soil water. The volume growing process was slightly affected by soil water. The fast time of DBH increment in wet habitat was longer than that in moderate-water habitat, the former was 6～15 year, the latter was 9～12 year. The mature age of DBH in moderate-water habitat was 1～2 year older than that in wet habitat. The fast time of height incerment in wet and moderate-water habitat was 6 year. The mature age of height in wet habitat was 3~6 year older than that in moderate-water habitat. The fast time of volume increment in wet and moderate-water habitat was excess to 24 year. The mature age of volume in wet and moderate-water habiat was also excess to 24 year.