石门台亚热带森林不同演替阶段冠层结构与林下光照特征

Characteristics of Canopy Structure and Understory Light in Subtropical Forest Community at Different Successional Stages in Shimentai Nature Reserve

以时空替代法在广东石门台自然保护区选择3种分别处于演替前期、中期、后期的森林群落为研究对象,探讨了亚热带森林群落在不同演替阶段的冠层结构与林下光照特征.结果显示:亚热带森林不同演替阶段冠层结构与林下光照差异均极显著(P<0.000 1),且随演替进展,其林冠开度和林下光照显著减少、叶面积指数显著增加(P<0.01).相关分析表明,林下光照因子与林冠开度呈显著正相关(P<0.01),与叶面积指数呈显著负相关(P<0.05).典型相关分析进一步表明,林冠开度对冠层结构的反映程度比叶面积指数高,冠层结构对林下散射光的影响比对直射光大.综合分析表明,随着演替进展,亚热带森林群落冠层逐渐郁闭,林下光照也随之减少,采用林冠开度评价冠层结构演替动态效果最佳,林下直射光比散射光变化更复杂.

Characteristics of canopy structure and understory light of subtropical forest community at different successional stages in Shimentai Nature Reserve were investigated with the study object of 3 forest communities in the early,middle and late stages of succession,respectively. The results showed that significant differences in canopy openness and understory total light were found at different successional stages（ P〈0. 000 1）. With succession progresses,canopy openness and understory light decreased significantly,and the leaf area index increased significantly（ P〈0. 01）. The correlation analysis showed that there was a significant positive correlation between undergrowth and canopy opening（ P〈0. 01） and a significant negative correlation with leaf area index（ P〈0. 05）. The canonical correlation analysis further showed that canopy openness reflected higher canopy structure than leaf area index,and the effect of canopy structure on understory light is greater than that of direct light. The comprehensive analysis showed that with the progress of succession,the canopy of the subtropical forest community was gradually closed,and the understory light also decreased. The canopy opening is the best method to evaluate the dynamics of canopy structure succession,and the understory light is more complex than the succession of diffuse light.