Effects of canopy species dominance on understorey light availability in low-elevation secondary forest stands in Costa Rica
Effects of canopy species dominance on understorey light availability in low-elevation secondary forest stands in Costa Rica
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DOI：
10.1017/s0266467400010038
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发表时间：
1996-11-01
影响因子：
1.4
通讯作者：
Chazdon, RL
中科院分区：
文献类型：
--
作者：
Kabakoff, RP;Chazdon, RL
在哥斯达黎加的大西洋低地的La Selva生物站，研究了Pentaclethra macroloba和Goethalsia meiantha，两个常见的树种，具有对比的树冠结构的次生林林下的光可用性的树冠物种优势的影响。在每六个12至16岁的演替林占主导地位的这些物种之一，相对丰度和断面积的焦点物种内确定20米× 50米的情节。在1米高度的光可用性进行了测量，在每个地块内使用Licor-2000植物冠层分析仪在27个位置，并通过分析半球形的照片在10个位置。在整个林分，平均叶面积指数值显着负相关与冠层开放度。林下微网站下Pentaclethra有显着较高的光的可用性比微网站下Goethalsia。然而，在整个看台上，光的可用性是不相关的，无论是总断面积或干密度大于或等于10厘米胸径的树木。这些结果表明，断面积和干密度的树木在上层的森林冠层是穷人的预测光穿透到下层。这里提出的一个假设是，密集的亚冠层和林下植被在热带次生林可以强烈影响林下的光水平。或者，上层森林树冠的透光率特性可能会受到树冠结构或树叶密度的物种特异性差异的影响，这些差异独立于树木的直径和密度。
The effect of canopy species dominance on understorey light availability in secondary forests was examined for Pentaclethra macroloba and Goethalsia meiantha, two common tree species with contrasting canopy architecture at La Selva Biological Station in the Atlantic lowlands of Costa Rica. In each of six 12- to 16-year-old successional stands dominated by one of these species, relative abundance and basal area of the focal species were determined within a 20 m x 50 m plot. Light availability at 1 m height was measured within each plot using a Licor-2000 Plant Canopy Analyzer at 27 locations and by analysing hemispherical photographs taken at 10 locations. Across stands, mean LAI values were significantly negatively correlated with canopy openness. Understorey microsites beneath Pentaclethra had significantly higher light availability than microsites beneath Goethalsia. Across stands, however, light availability was not correlated with either total basal area or stem density of trees greater than or equal to 10 cm DBH. These results indicate that basal area and stem density of trees in the upper levels of the forest canopy are poor predictors of light penetration to the understorey. One hypothesis suggested here is that dense subcanopy and understorey vegetation in tropical secondary forests can strongly influence understorey light levels. Alternatively, light transmittance characteristics of the upper forest canopy may be influenced by species-specific differences in canopy architecture or foliage density that vary independently from tree diameter and density.