Conversion of total to projected leaf area index in conifers
Conversion of total to projected leaf area index in conifers
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DOI：
10.1139/cjb-78-4-447
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发表时间：
2000-04-01
期刊：
影响因子：
--
通讯作者：
Goodman, D
中科院分区：
文献类型：
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作者：
Barclay, HJ;Goodman, D
叶面积指数(LAI)目前有几个定义，但它们之间的关系并不清楚。为了比较各种研究的结果，需要从一种定义转换为另一种定义。提出了6种针叶树种叶面积指数在4种定义之间的换算因子：大冷杉Abies Grand is(Dougi.Don)Lindl.、褶皱Thuja plicata donn ex D.Don.、异叶铁杉Tsuga Heterophylla(Raf.)Sarg.、西氏云杉Picea Sitchens(Bong.)Carr.)、圆叶松(Pinus Conorta Dougl.)和油松(Pseudotsuga menziesii(MIRB)France)。在叶面积指数的四种定义中，两个极端涉及(I)叶的总面积和(Ii)非水平叶在树上的投影面积。如果树叶在空间中的方向是随机的，那么定义I和II之间的转换系数应该是0.25。这六种植物中有四种的转换系数非常接近这个值，这四种植物中有三种相对不耐阴。剩下的两个物种，大沙棘和褶皱沙棘，由于其叶片的大致水平方向，其转换系数约为0.35。这两种植物都是相对耐荫的，而水平叶的趋势可能是一种适应，以帮助耐荫。敏感度分析表明，当光线几乎从头顶直射过来时，大多数树种的树叶都能最大限度地增加收集的光量，就像许多遮荫的林木一样。
Several definitions of leaf area index (LAI) presently exist in the literature but the relationships among them are not clear. To compare the results of various studies, there is a need to convert from one definition to another. Factors for converting among four definitions of LAI are presented for six conifer species: Abies grandis (DougI. ex D. Don) Lindl., Thuja plicata Donn ex D. Don., Tsuga heterophylla (Raf.) Sarg., Picea sitchensis (Bong.) Carr.), Pinus contorta Dougl., and Pseudotsuga menziesii (Mirb) France). Among the four definitions of LAI, the two extremes involve (i) the total area of the leaf and (ii) the projected area of nonhorizontal leaves, as they occur on the tree. If leaves are randomly oriented in space, then the conversion factor between definitions i and ii should be 0.25. Four of the six species have conversion factors very close to this value, and three of these four are relatively shade-intolerant. The remaining two species, A. grandis and Thuja plicata, have conversion factors of approximately 0.35, owing to the approximately horizontal orientation of their leaves. These two species are both relatively shade-tolerant, and the trend toward horizontal leaves might be an adaptation to assist in shade tolerance. A sensitivity analysis indicated that the foliage of most of the species maximized the amount of light gathered when the light was coming from almost straight overhead, as is the case with many shaded forest trees.