Are the “ seeds ” of spatial variation in cyclic dynamics apparent in spatially-replicated short time-series ? An example from the forest tent caterpillar

Abstract

Roland, J. 2005: Are the “seeds” of spatial variation in cyclic dynamics apparent in spatially-replicated short time-series? An example from the forest tent caterpillar. — Ann. Zool. Fennici 42: 397–407. Variation in the pattern of dynamics of the forest tent caterpillar was assessed over a 13-year interval of population collapse and increase among 68 sites within a 420 km 2 region. Patterns of population change were compared with the level of forest fragmentation among sites, and interpreted in light of previous studies on the effect of forest fragmentation on the impact of natural enemies of forest tent caterpillar. Outbreaks peaked earlier in contiguous forests than in fragmented forests, and collapsed more rapidly. Parameters of population change for populations in contiguous forests were more characteristic of strongly cyclic dynamics than were those in more fragmented forests, reflecting a significant effect of forest structure on the lagged density-dependent component of tent caterpillar dynamics. Despite the relative shortness of these time series the patterns identified are consistent with a reduction in efficacy of natural enemies in more fragmented forest habitats.