Models of Clonal Plant Growth Based on Population Dynamics and Architecture
Models of Clonal Plant Growth Based on Population Dynamics and Architecture
复制标题
基于种群动态和结构的克隆植物生长模型
作者：
T. Callaghan;B. Svensson;H. Bowman;D. Lindley;B. Carlsson
石松（Lycopodium annotinum）是一种具有匍匐茎/根茎生长形式的模块化克隆维管隐花，其分支模式是使用建筑和种群动态模型的组合进行模拟的。有关形态、存活和繁殖力的数据是在瑞典拉普兰实地收集的，并用于在两个模型中生成一系列生长规则。最初的、简单的、确定性的生长模型反映了 L. annotinum 在均匀环境中的生长形式。从该模型得出的结论是，顶端优势和分枝角度是两个重要的内部控制，它们优化了地面利用和避免植物内部对光、水和养分的竞争之间的平衡（植物被定义为由活组织物理连接的树枝的聚集体）。根据现场数据，将随机元素引入模型中，产生了各种模拟植物形态，与现场的植物形态明显可比。模拟植物的横向蔓延形状差异很大，从紧凑、密集、一年生节短的形式到松散、广泛传播、长一年生节的形式。游击队和方阵生长形式在模拟中都发生，只是作为随机过程的一部分。克隆（即来自共同祖先的植物聚集体）的存活时间从 1 年到模拟持续时间不等，表明它们具有无限生长的潜力，尽管相当数量（51%）仅存活 2 至 5 年。基于种群动态的架构模型非常稳健，敏感性分析表明，在克隆做出反应之前，生存概率必须改变 20%，而繁殖力值需要更大程度的变化（-100% 到 +50%）才能克服模型的随机因素。这反映了克隆植物所建议的鲁棒性，这也通过它们来自转移概率矩阵的低敏感性值来表明，但与一般转移概率矩阵的高敏感性形成鲜明对比。敏感性分析还表明，最敏感的年龄组是 2 至 6 岁。随机模型的一个主要限制是特定年龄死亡和繁殖的种群过程、根产生和节段伸长的生长过程以及植物的几何形状都“不智能地”变化。现在需要一种机械方法将这些过程与环境变量和内部反馈联系起来。
The branching pattern of Lycopodium annotinum, a modular and clonal vascular cryptogam with a stoloniferous/rhizomatous growth form, was simulated using a combination of architectural and population dynamics models. Data on morphology, survival and fecundity were collected in the field in Swedish Lapland and used to generate a series of growth rules in two models. An initial, simple, deterministic growth model reflected the growth form of L. annotinum in a homogeneous environment. From this model, conclusions were drawn that apical dominance and branching angles are two important internal controls which optimize the balance between ground exploitation and the avoidance of competition for light, water and nutrients within plants (plants being defined as the aggregations of branches physically connected by living tissues). The introduction of stochastic elements into the model, based on field data, produced a wide range of simulated plant forms, clearly comparable to those in the field. Lateral spread in simulated plants varied greatly in shape, from compact, dense forms with short annual segments to loose widely spread forms with long annual segments. Both guerilla and phalanx growth forms occurred in the simulations simply as part of a stochastic process. Survival of clones (i.e. aggregations of plants from a common ancestor) varied from 1 yr to the duration of the simulation, indicating their potential for indefinite growth, although a substantial number (51%) survived for only 2 to 5 yr. The architectural model based on population dynamics was robust and a sensitivity analysis showed that survival probabilities had to be changed by 20% before the clone reacted, while a much greater degree of change of fecundity values was required (-100% to +50%) to overcome the stochastic element of the model. This reflects the robustness suggested for clonal plants also indicated by their low sensitivity values from transition probability matrices, but is in marked contrast to the great sensitivity of transition probability matrices in general. The sensitivity analysis also showed that the most sensitive age classes were 2 to 6 yr. A major limitation of the stochastic model is that the population processes of age-specific death and fecundity, the growth processes of root production and segment elongation, and the geometry of the plant all vary "unintelligently". A mechanistic approach is now required to relate these processes to environmental variables and internal feedback.