Population dynamics of Aster kantoensis based on a multi-layer lattice model

构建了关东紫菀种群动态和灭绝风险的多层格点模型，分别对应于整体种群、区域种群和局部种群三个层次。种子传播是在这三个层次上考虑的。对于洪水特征，我们改变了它们在一个区域内的规模、频率、同步和发生地点。利用投影矩阵计算了小、大莲座和开花三个阶段的局部种群过程。假设由于其他多年生植物的入侵（盖度：β），在局部开放斑块被洪水淹没后，幼苗的发芽率和建立率随时间而下降。我们假设在一定时间（生境恶化时间：dtime）后没有幼苗不能建立。参数值通过实地调查和公布的记录估计。灭绝风险计算为100个重复x 10个系列中100年后的灭绝频率。仿真结果表明，该模型具有较好的描述能力，β和dtime参数值对消光风险影响较大。从洪水的时空特征来看，发生地点对洪水灭绝风险的影响较大，洪水地点的固定性使洪水灭绝风险显著增高。利用该模型，我们可以发现影响关东紫菀灭绝风险的重要因素。

A multi-layer lattice model was constructed for assessing population dynamics and extinction risk of Aster kantoensis, corresponding to three levels : a whole meta-, regional, and local populations. Seed dispersal was considered at these three levels. For flood characteristics, we changed their scale, frequency, synchronization, and occurrence sites within a region. A local population processes were calculated with a projection matrix based on three stages : the small and large rosettes and the flowerings. Germination rate and establishment of seedling was assumed to decline depending on time after a local open patch emergence by a flood, because of other perennial plants invasion (coverage rate : β). We assumed that no seedlings cannot establish after a certain time (habitat deterioration time : dtime). Parameter values were estimated by field surveys and published records. Extinction risk was calculated as the extinction frequency after 100 years among 100 replicates x 10 series.Simulation results showed that the present model has high descriptive ability and that the parameter values of β and dtime influence greatly on the extinction risk. For spatio-temporal characteristics of floods, the occurrence sites affected on the extinction risk largely and the fixation of the flood sites made the risk high eminently. Using the present model, we could detect important factors that influence largely the extinction risk of Aster kantoensis.