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Modelling epiphyte metapopulation dynamics in a dynamic forest landscape


  • T. Snäll,

  • J. Pennanen,

  • L. Kivistö,

  • I. Hanski

T. Snäll, Dept of Mathematics and Statistics, P.O. Box68 FI-00014, Univ. of Helsinki, Finland. ( – J. Pennanen, Dept of Forest Ecology, P.O. Box 27, FI-00014, Univ. of Helsinki, Finland. – L. Kivistö and I. Hanski, Dept of Biological and Environmental Sciences, P.O. Box 65, FI-00014, Univ. of Helsinki, Finland.


We combine simulations with spatial statistics to estimate the parameters of a metapopulation model for the epiphytic lichen Lobaria pulmonaria specializing on aspen (Populus tremula) and goat willow (Salix caprea) in Fennoscandian boreal old-growth forests. We estimated the parameters of a forest landscape model (FIN-LANDIS) by repeatedly running simulations and selecting the set of parameters for tree ecology and fire regime that reproduced empirical host tree density and spatial patterns. Second, we tested which variables were important in epiphyte colonization and estimated the dispersal kernel. Third, we run a metapopulation model for the lichen across the estimated landscape scenarios and selected values for the remaining parameters that reproduced the empirical patterns of epiphyte occurrence. There was little variation in predicted dynamics, occupancy and spatial patterns between replicate metapopulation simulations. However, more data would be required for accurately estimating the parameters of FIN-LANDIS primarily because of the inherent stochasticity in large scale forest fires. Following the beginning of fire suppression in the study area 150 years ago, the model predicts that lichen occupancy first increases but subsequently declines. The lower occupancy in the past than at present is explained by high rate of tree destruction by fires, which increases local extinction rate in patch-tracking metapopulations. In the absence of fires, the occupancy increases because of lower extinction rate, but without forest fires or alternative means of host tree regeneration, the lichen is predicted to go ultimately extinct because of severely reduced density of aspen and goat willow.