Effects of Understory Foliage on Patterns of Light Attenuation near the Forest Floor
Effects of Understory Foliage on Patterns of Light Attenuation near the Forest Floor
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林下树叶对森林地面附近光衰减模式的影响
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发表时间：
2004
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影响因子：
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通讯作者：
R. Montgomery
中科院分区：
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作者：
R. Montgomery
林下光照可利用性是林冠育苗环境的重要组成部分。了解是什么导致林下光可获得性的变化，是理解调节苗木银行的过程的一个步骤，苗木银行是热带森林更新的开始资本。在森林地面附近，光可利用性的变化可能会受到林下植被的结构和组成的强烈影响。我研究了五个新热带森林(哥斯达黎加La Selva生物站=LS；巴拿马巴罗科罗拉多自然纪念碑=BCI；秘鲁马努国家公园Cocha Cashu生物站=CC；巴西马瑙斯41公里=KM41；法属圭亚那Nouragues=NG)的落叶丰富和光衰减模式。我使用半球树冠照片估计了森林地面以上两个高度(0.65米和1.7米)的光照可用性，并计算了这两个高度之间的树叶数量。不同站点之间的光照可用性差异很大，站点排名取决于测量高度。在0.65m处，NG的平均光可利用性显著低于CC，KM41、LS和BCI相当于和居中。在1.7m处，NG的光能利用率仍然最低，CC的光能利用率最高，但LS的水平与CC相似，而KM41和BCI仍处于中等水平。在不同地点，光衰减与树叶密度呈正相关。LS林下落叶最多，在0.65~1.7m范围内光衰减最大，KM41、NG和CC的落叶量中等，光衰减中等。BCI的林下叶密度最低，两个测量高度的光照差异不大。结果表明，林下树叶对林下光照有显著影响，不同立地林木苗木的选择环境不同。
Understory light availability is an important component of the environment for canopy tree seedlings. Understanding what generates variation in Understory light availability represents one step in understanding processes regulating seedling banks, the beginning capital of regeneration in tropical forests. Near the forest floor, variation in light availability may be strongly influenced by the structure and composition of the understory. I examined abundance of Understory foliage and patterns of light attenuation in five Neotropical forests (La Selva Biological Station, Costa Rica = LS; Barro Colorado Nature Monument, Panama = BCI; Cocha Cashu Biological Station, Manu National Park, Peru = CC; Kilometer 41, Manaus, Brazil = KM41; and Nouragues, French Guiana = NG). I used hemispherical canopy photos to estimate light availability at two heights (0.65 and 1.7 m) above the forest floor and counted foliage between these heights. Light availability differed significantly among sites, and site rankings depended on measurement height. At 0.65 m, NG had significantly lower mean light availability than CC, with KM41, LS, and BCI equivalent and intermediate. At 1.7 m, light availability was still lowest at NG, and highest at CC, but LS had levels similar to CC while KM41 and BCI remained intermediate. Across sites, light attenuation was positively related to foliage density. LS had the most understory foliage and the highest light attenuation between 0.65 and 1.7 m. KM41, NG and CC had intermediate amounts of foliage and intermediate light attenuation. BCI had the lowest density of understory foliage and no difference between light at the two measurement heights. My results show significant effects of understory foliage on understory light and indicate that the selective environment of canopy tree seedlings differs among sites.