山地落叶阔叶林优势树种米心水青冈幼苗的定居

在郁闭的林冠下、模拟林窗和林间空旷地3种光照环境中，研究了施肥和未施肥的米心水青冈幼苗生存和生长发育过程．结果表明，幼苗在林下的发育受到光照不足的严重抑制，生长在林下的幼苗比生长在林窗和空旷地幼苗死亡快，死亡率高，幼苗在郁闭林下能够生存的时间不超过12周．施肥处理的幼苗比对照的幼苗死亡快，死亡率高．幼苗死亡很可能与土壤中的病原生物有关．虽然由林下光照强度增加到模拟林窗的光照强度后，幼苗发育有明显改善，但幼苗在模拟林窗环境和空旷地的生长没有显著差异．结果说明，米心水青冈新出土的幼苗在郁闭林冠下易受伤害，更新立苗阶段需要有比较好的光照条件，肥沃土壤可能也无助于改善郁闭林冠下幼苗的定居．

Seedling establishment of Fagus engleriana ,a dominant in mountain deciduous forests

The survival and growth of Fagus engleriana seedlings in three light levels,and with and without supplying additional fertilizer (F 1 and F 0, respectively) for each light level were studied. The three light levels were to simulate the light regimes in the understorey, small gaps and clearings (L 1, L 2 and L 3 about 1%, 18% and 100% of full sunlight, respectively).The seedling development in L 1 was severely inhibited by low light intensity. Seedling mortality was remarkably higher in L 1 than in L 2 and L 3, and in F 1 than in F 0. The death of the seedlings seemed to result from attack of fungal pathogens. Although seedling survival and growth were significantly improved as light intensities increased from L 1 to L 2, seedlings in L 3 developed similarly as those in L 2. It is suggested that the young seedlings could not tolerate the shade of closed forest canopy, and fertile patches on the forest floor might not improve seedling establishment.Successful regeneration of the species in the forests needs better light conditions such as those in gaps than those under the closed forest canopy, at least during the phase of seedling establishment.