巴山松针叶群体数量和寿命的水平与垂直变化趋势分析

HORIZONTAL AND VERTICAL FLUCTUATION OF NUMBER AND LONGEVITY OF LEAF POPULATIONS IN HENRY PINE(PINUS HBNRYI)FOREST

根据对巴山松针叶群体的水平和垂直变化特征及趋势进行的研究，得到如下结果：（１）单株木的针叶总数和各龄针叶总数随胸径增加而增多，随密度增加而减少；当年生针叶数量所占比例随径阶增加而增大，２年生针叶比例与此相反，而１年生和３年生针叶比例基本保持稳定。（２）单株木的径阶愈小，针叶平均寿命亦愈长；就针叶平均生存期限而言，劣势太最短，优势木次之，而平均木最长。（３）各龄级针叶群体的数量一般在树冠中部所占比例最大，下部所占比例次之，上部比例最小。在林分中处于不同地位的林木表现形式略有差异，与树冠内光照的分布有关。（４）针叶的内禀增长率随着径阶的增大、树高的增加及相对光照强度的增高而增加；树冠中针叶的平均寿命随树高增加而减小。另外，对产生上述结果的原因也进行了部分探讨。

I analyzed the horizontal and vertical dynamic characteristics,fluctuating trends and the demography of leaf populations of Henry pine stands,and ob-tained tlie following results: (1)The leaf nuniber per tree and number of leaves of varying ages inc-reased with stem diameter,but decreased with stand density.The percentageof current-year leaves Incrcased with stem diameter, but the opposite was truefor 2-year-old leaves,The ratio of 1-year-old leaves to 3-year-old leavds kept stable. (2)The stem diameter was negatively correlated to the leaf life expect-ancy.The life expectancy of the leaves in the inferior trees were the shortest,and the average trees the longest,while the dominant trees fell in between.(3) Generally,the number of leaves of,varying age classes was highest in the middle part of the canopy,but difference existed in the structure ofleaf populations among tree types.This could be ascribed to the light eondi-tions in the canopy. (4)The intrinsic rate of increase of the leaf ppulations increased withstem diameter,tree height and relative light intenstity in the canopy.The lifeexpectancy of leaves in different branck cohorts decteas with tree height.It was inferred that the life expectancy of leaves in the same in the branch cohortwould increase with branch age.