林窗大小和位置对丽江云杉自然更新幼苗存活和生长的影响

通过 1997～ 2 0 0 0年对 32个林窗的连续观测调查 ,研究了滇西北玉龙雪山自然保护区云杉坪亚高山丽江云杉林林窗大小和林窗位置对自然更新幼苗存活和生长的影响 .4个生长季节的观测结果表明 :林窗与林下非林窗内的幼苗大小和幼苗存活数量差异明显 .林窗由小到大 ,单位面积内的自然更新苗木数量逐渐减少 ,小林窗中更新苗为大林窗的 5倍左右 ,而林下的更新苗很少 ,0 .2ind .10m-2 .中等林窗和小林窗内的幼苗数量在从南到中心到北的位置上几乎没有明显的差异 ;大林窗中存在由南到北的位置差异 ,更新幼苗数量逐渐减少 .从更新幼苗的生长来看 ,中等林窗内的幼苗 ,高度最大、生长最快 ,定居阶段的平均年高生长为 (7.1± 0 .5 )cma-1,小林窗次之 ,大林窗和林下幼苗个体最小 ,生长最慢 .进一步从林窗位置来看 ,中、小林窗幼苗大小几无位置差异 ,大林窗则由南到北 ,幼苗由大变小 .从幼苗存活数量和大小来看 ,中等林窗大小是丽江云杉幼苗更新的适宜面积 ,对该类型退化亚高山针叶林恢复提供了一定的参考 .图 4表 2参 2 3

ON THE SURVIVAL AND GROWTH OF NATURALLY REGENERATED PICEA LIKIANGENSIS SEEDLINGS

The survival and growth of Picea likiangensis seedlings were investigated for 4 years in variously sized canopy gaps and with-in gap position on the Yulong Snow Mountain in northwestern Yunnan, China. There are small (gap area<50 m2), medium (gap area 50～100 m2) and large (gap area>100 m2) gaps in P. likiangensis forest, and they account for 25%, 41% and 34%, respectively. The experiment was conducted in the three different sized gaps and understorey, and with-in gap position (north, south and center) in each gap. The seedlings were originated from natural seed rain. The results showed that there were significant differences in size and number of seedlings between gap and understorey. After four growing seasons, seedlings in large gaps were found 5 times more than in small ones, but those in control areas were seldom found (only 0.2 ind.10 m-2). The survival of P. likiangensis tended to reduce from south through center to north positions within the larger gaps, whereas it was not varied with-in gap position in small and medium ones. The seedling size in terms of height and basal diameter in different sized gaps were as: medium > small > large > understorey, and so was relative growth rate. The average annual growth of height was (7.1±0.5) cm in medium gaps. The size of seedlings was not different with-in gap position in medium and small gaps, but seedling height peaked just south of gap and declined towards the center, north edges in large gaps. The seedling establishment was greater in gaps than in closed-canopy areas. Due to adapt to light condition in medium gaps the seedling's relative growth rate was the greatest, but was relatively low relative growth rate in portion of large gaps more exposed to direct solar radiation as well as in the portion of small gaps shaded to weak solar radiation. The author suggests that medium gap size be suitable for regeneration of P. likiangensis forest based on the changes of survival and growth of seedlings for four growing years in the early period. Fig 4, Tab 2, Ref 23