Biomass allocation and light partitioning among dominant and subordinate individuals in Xanthium canadense stands
Biomass allocation and light partitioning among dominant and subordinate individuals in Xanthium canadense stands
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DOI：
10.1006/anbo.1998.0729
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发表时间：
1998-11-01
期刊：
影响因子：
4.2
通讯作者：
Hirose, T
中科院分区：
文献类型：
--
作者：
Anten, NPR;Hirose, T
研究了密集林分和孤立林分植物的地上生物量分配和光捕获模式与林分高度的关系。建立了一个冠层模型来计算单株植物的光吸收。该模型结合了双子叶一年生苍耳（Xanthium canadense Mill）的林分结构、单生植物和不同高度植物的生物量分配模式。有4个林分，林分高度随林龄和养分有效性的增加而增加。林分植物与孤立生长植物之间以及林内不同高度植物之间的高质量异速生长关系存在显著差异。随着株高的增加，叶片中茎部质量的比例呈下降趋势，但单生植株的LMR高于同高度竞争植株。因此，与先前的假设相反，竞争植物的LMR并不是严格由生物力学约束决定的，而是由响应竞争的生物量分配的塑性变化引起的。单位叶质量平均叶面积（SLA）随光合光子通量密度（PPFD）的增加而降低，与养分有效性无关。因此，林分中较高、较占优势的植物的叶面积比（LAR: LAR = LMR x SLA）低于较矮、较次要的植物。优势植物单位叶面积（Phi（面积））和单位质量（Phi（质量））吸收的光都比劣势植物多。它们的较大的Phi（面积）超过了较低的LAR （Phi（质量）= Phi（面积）x LAR）。我们得出结论，优势植物的较大Phi（质量）是定量证据，表明竞争光的成功与茎的大小不成比例地相关（即不对称竞争）。据我们所知，没有其他研究证明了这一点，并定量估计了光获取与植物大小的关系。这一结果与以往在多特定林分中优势种和从属种的Phi（质量）相似的研究结果形成了对比，并讨论了为什么光竞争在单特定林分中是不对称的，而在LAI相似或更大的多特定林分中是大小对称的。(C) 1998年植物学年鉴。
Patterns of above-ground biomass allocation and light capture by plants growing in dense stands or in isolation were studied in relation to their height. A canopy model was developed to calculate light absorption by individual plants. This model was combined with data on canopy structure and patterns of biomass allocation for solitary plants and for plants of different heights in dense mono-specific stands of the dicotyledonous annual Xanthium canadense Mill. There were four stands, and stand height increased with age and nutrient availability. The allometric relationship between height and mass differed considerably between plants in stands and those growing in isolation and also between plants of different heights within stands. The proportion of shoot mass in leaf laminae (LMR) decreased with increasing plant height, bur solitary plants had a higher LMR than competing plants of the same height. Thus, in contrast to previous assumptions, LMR of competing plants is not strictly determined by biomechanical constraints but results from a plastic shift in biomass allocation in response to competition. Average leaf area per unit leaf mass (SLA) decreased with increasing photosynthetic photon flux density (PPFD) independent of nutrient availability. Consequently, taller, more dominant plants in stands had a lower leaf area ratio (LAR: LAR = LMR x SLA) than shorter, more subordinate plants. Dominant plants absorbed more light both per unit leaf area (Phi(area)) and per unit mass (Phi(mass)) than subordinate plants. Their greater Phi(area) more than compensated for a lower LAR (Phi(mass) = Phi(area) x LAR). We conclude that the greater Phi(mass) of dominant plants is quantitative evidence that success in competing for light is disproportionately related to the size of the shoot (i.e, asymmetric competition). We know of no other study which has demonstrated this with quantitative estimates of light acquisition in relation to plant size. This result is contrasted with previous studies on multi-specific stands in which Phi(mass) of dominant and subordinate species is similar, and we discuss why light competition in mono-specific stands is asymmetric whereas it can be size-symmetric in multi-specific stands, with similar or greater LAI. (C) 1998 Annals of Botany Company.