不同林分下胖大海幼树幼苗更新分布格局

Distribution pattern of Sterculia lychnophora saplings regeneration in the different forest stands

以越南东南部胖大海天然更新林为研究对象,运用6个聚集度指标分析不同林分优势度和郁闭度等级下胖大海幼树幼苗更新3个阶段的空间分布格局特征,并运用Iwao回归方程和Taylor幂法则模型进行检验,比较胖大海的出现相对频率(Ey)在不同林分优势度和郁闭度等级下的差异性。结果表明:胖大海幼树幼苗的空间分布型呈聚集分布型;不同林分优势度和郁闭度等级对胖大海幼树幼苗更新的影响在第2、第3阶段的Ey存在显著性差异,而在第1阶段差异性不显著;胖大海在优势度低级的Ey,在第1阶段分别是优势度中级和高级的1.05和1.17倍,在第2阶段为优势度高级的30%,在第3阶段分别为优势度中级和高级的99%和31%;胖大海在郁闭度1级的Ey,在第1阶段分别是郁闭度2、3和4级的85%、1.32倍和75%,在第2阶段分别是郁闭度2、3和4级的1.80、1.97倍和69%,在第3阶段依次为郁闭度2、3和4级的1.29、1.10倍和43%。胖大海幼树幼苗基本适应高郁闭度林分,对光照强度要求较低。

The objective of this study is the natural regeneration of Sterculia lychnophora Hance under different forest dominance levels in Southeast of Vietnam, the spatial distribution pattern characteristics of 3 phases of S. lychnophora regeneration were analysed by using 6 aggregate indexes under the different forest dominance and the canopy density levels, and were tested by using Taylor＇s and Iwao＇s models; and the differences of appearance relative frequency of the S. lychnophora natural regeneration under different forest dominances and canopy density levels were compared. The results showed as follows. The distribution pattern of S. lychnophora saplings was an aggregate pattern. The appearance relative frequency of S. lychnophora saplings in the second and third phases under different forest dominances and canopy density levels were of significant difference, but in the first phase the difference was insignificant. The appearance relative frequency of S. lychnophora under the first dominance levels was 1.05 and 1.17 times compared to that under the second and third dominance levels in the first phase, 0.30 times compared to that under the third dominance level in the second phase, 0.99 and 0.31 times compared to that under the second and third dominance levels in the third phase. The appearance relative frequency under the first canopy density levels was 0.85, 1.32 and 0.75 times compared to that under the second, third and fourth levels in the first phase, 1.80, 1.97 and 0.69 times compared to that under second, third and fourth canopy density levels in the second phase, 1.29, 1.10 and 0.43 times compared to that under second, third and fourth canopy density levels in the third phase. The saplings of S. lychnophora adapted basically to the forest stand of high canopy density levels, and required lower light intensity.