Gillman M, Bullock J M, Silvertown J, Hill B Clear
Department of Biology, The Open University, Walton Hall, MK7 6AA, Milton Keynes, UK.
Oecologia. 1993 Nov;96(2):282-289. doi: 10.1007/BF00317743.
Two versions of a stage-structured model of Cirsium vulgare population dynamics were developed. Both incorporated density dependence at one stage in the life cycle of the plant. In version 1 density dependence was assumed to operate during germination whilst in version 2 it was included at the seedling stage. Density-dependent parameter values for the model were estimated from annual census data in a factorial grazing experiment. Version 1 of the model produced significant estimates of density dependence under field conditions. The estimated values, when included in a simulation of the dynamics, produced two-point limit cycles under conditions of hard grazing. The limit cycles were most pronounced at the early rosette stage. Comparison of the effects of density dependence at the two different stages in the life cycle revealed a strong difference in predicted dynamics. This emphasizes the importance of determining where density dependence operates under field conditions and the potential problems of arbitrarily assigning it to particular life-history stages. Version 1 of the model produced a good prediction of observed mean plant density across the different grazing treatments (r =0.81, P<0.001).
开发了两种版本的毛蓟种群动态阶段结构模型。两者都在植物生命周期的一个阶段纳入了密度依赖性。在版本1中，假定密度依赖性在发芽期起作用，而在版本2中，它包含在幼苗期。该模型的密度依赖性参数值是根据一项析因放牧实验中的年度普查数据估算得出的。模型的版本1在田间条件下得出了密度依赖性的显著估算值。这些估算值纳入动态模拟后，在重度放牧条件下产生了两点极限环。极限环在莲座叶早期最为明显。对生命周期中两个不同阶段密度依赖性影响的比较揭示了预测动态方面的显著差异。这强调了确定田间条件下密度依赖性作用位置的重要性，以及将其任意分配到特定生活史阶段的潜在问题。模型的版本1对不同放牧处理下观察到的平均植株密度做出了良好预测（r = 0.81，P<0.001）。
