Mesoscale distribution of understorey plants in temperate forest (Kalø, Denmark): the importance of environment and dispersal

Abstract

We studied the influence of environmental heterogeneity and dispersalprocesses on mesoscale distribution patterns of understorey plants in a 330ha ancient, managed temperate forest area. Similarity matrixregression analysis showed that overall species similarity was affected bysite(the two disjunct halves of the forest area), spatial autocorrelation at the100m scale, edaphic conditions, stand type and stand structure, andthe occurrence of open areas, but not by stand age or topography. Usingautologistic regression we analysed the influence of clumping, site, edaphicconditions, stand composition, open areas, and stand structure on theindividualdistribution patterns of the 60 most abundant species. Only five species haddistributions that were not significantly related to any of the explanatoryvariables. A large number of species showed significant, and often differing,relationships to at least one of the environmental parameters. At least 20species exhibited clumping at the 100 m scale that was independentof the environmental parameters. Principal coordinate analysis and an analysisusing the Ellenberg ecological indicator values suggested that no importantgradients had been overlooked. Dispersal ability (estimated from dispersalmode)and clumping independent of environmental heterogeneity were related. Poordispersers exhibited stronger clumping at the 100 m scale thangooddispersers. Our results support the joint importance of environmentalheterogeneity and dispersal processes in shaping the mesoscale distributionpatterns of forest herbs. We conclude that the distribution of plant species,and species coexistence and species composition in plant communities, cannot beexplained without simultaneously considering environmental heterogeneity anddispersal.