An integrated analysis of the spatio-temporal colonization patterns of forest plant species

An integrated analysis of the colonization patterns of forest plant species was carried out in a 34-ha, mixed deciduous forest in northern Belgium. First. we sought to describe the relationships between land use history and environmental conditions. Land use history and soil type were related and negative correlations between pH and secondary forest age were found. The density of the shrub layer increases with secondary forest age. Litter quantity and cover of Urtica dioica were mainly indirectly influenced by land use history. Litter starts accumulating at low pH values and high shrub density and Urtica dioica grows vigorously on nutrient enriched soils where much light can reach the ground. Next, the importance of these human-altered environmental conditions for the colonization of forest plant species was assessed relative to the importance of dispersal limitation. Therefore, the distribution of 16 forest species was mapped and species-specific spatio-temporal isolation measures were calculated. The analysis revealed that the colonization patterns of the slowly colonizing species (i.e. 'ancient forest plant species') are best explained by a combination of spatio-temporal isolation, soil type, pH and the (non-)cover of Urtica dioica. By contrast, spatio-temporal isolation was never a limiting factor for good colonizing forest species. Our results suggest that co Ionization of 'ancient forest plant species' is hampered by a combination of dispersal and recruitment limitation and that the relative importance of both factors is species-specific.