LAUSR

This study tested the assumption that in mixed-species deciduous forests, shade tolerance determines the species’ role in forming vertical structuring of the canopy layer and that persistence of light-adapted species in such forests is conditioned by the occurrence of larger disturbances and simple vertical structures. Several spatially explicit structural attributes were compared in the neighbourhood of eight tree species (Alnus glutinosa (L.) Gaertner, Carpinus betulus L., Fraxinus excelsior L., Pinus sylvestris L., Quercus robur L., Tilia cordata Miller, Ulmus laevis Pall., Ulmus minor Miller) with different shade tolerance growing in uneven-aged forests. The analysis indicated that although species light requirements were loosely related to the density and structural attributes of the stand patches in which the species occur, the light-adapted species tended to avoid close proximity to the shade-tolerant species. These results suggest that under-canopy trees of light-adapted or mid-tolerant species may survive successfully in heterogeneous canopies in the neighbourhoods of species with similar or higher light requirements. Hence, controlling the admixture of shade-tolerant species may be crucial for the persistence of light-adapted species in uneven-aged forests. The results also indicate that in the mixed-species deciduous forests of Central Europe, complex vertical structures arise not only in larger areas of several hundred square metres but also on small spatial scales corresponding to the projection area of canopy trees and suggest that maintaining species diversity in such forests may not require application of management systems based on extensive canopy openings.