The stratification theory for plant coexistence promoted by one-sided competition
The stratification theory for plant coexistence promoted by one-sided competition
复制标题
DOI：
10.1111/j.1365-2745.2009.01490.x
复制
发表时间：
2009-05-01
影响因子：
5.5
通讯作者：
Takada, Takenori
中科院分区：
文献类型：
--
作者：
Kohyama, Takashi;Takada, Takenori
植物的一个基本特征是，较高水平的叶子比较低水平的叶子更容易获得光。因此，较大的植物通常比较小的植物在争夺光线方面更成功。本文利用一个简单易行的分层种群模型，分析了这种大小不对称或单边竞争对植物种间成功共存的影响。在该模型中，同一层中的植物表现出与任何其他植物相同的拥挤效应，而与物种无关。一个上层繁殖，下层幼年的两层种群具有唯一稳定的（植物大小加权）平衡密度，只要其繁殖力足以补偿其死亡率。我们还计算了一个独特的阈值低层密度的分层种群时，没有上层植物。除完全双边竞争情况外，该阈值下层物种密度大于与上层物种的加权平衡密度，两层物种可以与单层下层物种稳定共存，而双边竞争则不能。共存条件是单层粒子的平衡密度介于阈值下层粒子密度和双层粒子的平衡密度之间。对于一个下层物种成功地与两层物种共存，任何优势的人口统计性能，最突出的是在一个足够高的繁殖力每株植物必须抵消不利的生活在黑暗的conditions.Results模型的多层种群表明，几个物种不同的最大层和繁殖力可以共存的条件下，单边竞争。我们展示了一个例子，稳定共存的八个物种。该模型预测的种间权衡对应于在雨林中观察到的模式。我们提出了一个分层理论，解释了植物物种的成功共存的生成和维护。在单侧竞争条件下，利用逃避林下竞争的冠层种群表现出入侵密度高于其平衡密度的林下种群的能力，这为高繁殖力和/或耐荫性的林下种群提供了共存的机会。共享最大冠层高度的物种的预测共存是最明显的热带雨林的树木。
It is an essential feature of plants that leaves at higher levels have better access to light than those at lower levels. Thus, larger plants generally enjoy greater success in competing for light than smaller ones. We analyse the effect of such size-asymmetry, or one-sided competition, on the successful coexistence of plant species, using an analytically tractable model for stratified populations, in which a plant in the same layer exhibits the same crowding effect as any other, irrespective of species.A two-layer population that is reproductive in upper layer and juvenile in lower layer has a uniquely stable (plant-size-weighted) equilibrium density, as long as its fecundity is sufficient to compensate for its mortality rate. We also calculate a unique threshold lower-layer density of this layered population when there is no upper-layer plant. This threshold lower-layer density is larger than the weighted equilibrium density with upper layer, except for the case of perfect two-sided competition.A two-layer species can stably coexist with a one-layer, understorey species as a result of one-sided, but not two-sided competition. The coexistence condition is that the equilibrium density of the one-layer species lies between the threshold lower-layer density and the equilibrium density of the two-layer species. For an understorey species to coexist successfully with a two-layer species, any advantage in demographic performance, most prominently in a sufficiently high fecundity per plant must offset the disadvantage of living in dark conditions.Results from a model of multi-layer populations suggest that several species differing in terms of maximum layer and fecundity can coexist under conditions of one-sided competition. We demonstrate an example of the stable coexistence of eight species. The inter-specific trade-offs predicted by the model correspond to patterns observed in a rain forest.Synthesis. We propose a stratification theory that explains the generation and maintenance of the successful coexistence of plant species. Under the condition of one-sided competition, a canopy population that takes advantage of escaping from understorey competition shows an ability to invade an understorey with a density higher than its own equilibrium density, and which offers opportunities for an understorey population with high fecundity and/or shade tolerance to coexist. The predicted coexistence of species that share maximum canopy height is most pronounced for trees of tropical rain forests.