Velázquez Jorge, Allen Robert B, Coomes David A, Eichhorn Markus P
School of Physics and Astronomy, The University of Nottingham, Nottingham NG7 2RD, UK Facultad de Ciencias Físico Matemáticas, Universidad Autónoma de Puebla, Puebla, Pue. 72001, México.
Landcare Research, P.O. Box 69, Lincoln 8152, New Zealand.
Proc Biol Sci. 2016 Jan 27;283(1823). doi: 10.1098/rspb.2015.2404.
Plant sizes within populations often exhibit multimodal distributions, even when all individuals are the same age and have experienced identical conditions. To establish the causes of this, we created an individual-based model simulating the growth of trees in a spatially explicit framework, which was parametrized using data from a long-term study of forest stands in New Zealand. First, we demonstrate that asymmetric resource competition is a necessary condition for the formation of multimodal size distributions within cohorts. By contrast, the legacy of small-scale clustering during recruitment is transient and quickly overwhelmed by density-dependent mortality. Complex multi-layered size distributions are generated when established individuals are restricted in the spatial domain within which they can capture resources. The number of modes reveals the effective number of direct competitors, while the separation and spread of modes are influenced by distances among established individuals. Asymmetric competition within local neighbourhoods can therefore generate a range of complex size distributions within even-aged cohorts.
种群内的植株大小常常呈现多峰分布，即使所有个体年龄相同且经历相同的环境条件。为了确定其成因，我们创建了一个基于个体的模型，在空间明确的框架下模拟树木生长，该模型使用来自新西兰森林长期研究的数据进行参数化。首先，我们证明不对称资源竞争是同种群内形成多峰大小分布的必要条件。相比之下，招募期间小规模集群的遗留影响是短暂的，并且很快就会被密度依赖的死亡率所掩盖。当成年个体在其能够获取资源的空间域内受到限制时，就会产生复杂的多层大小分布。峰的数量揭示了直接竞争者的有效数量，而峰的间距和离散程度则受成年个体之间距离的影响。因此，局部邻域内的不对称竞争甚至可以在同龄种群中产生一系列复杂的大小分布。
