Seasonal variation in the seed banks of native woodland and coniferous plantations in Northern Spain

The effect of forest type (native woodland and two types of plantation: eve rgreen coniferous Pinus radiata D. Don and deciduous coniferous Larix kaemp feri Lamb.) and season on the composition and density of the soil seed bank were studied in a replicated experiment in the Basque Country, northern Sp ain. Spring was the season with the largest germinable seed bank and the hi ghest species diversity. The seasonal variation of the seed bank was mainly due to the phenology of the species rather than to the environment (i.e. t ree species). The highest number of seeds and species in the seed bank was found in the larch plantation. The greatest similarity among the seed bank of the different forests was due to the presence of broad ranged species. S pecies belonging to this group were mainly present in the seed bank. The pr esence of seeds of some native held layer species such as Arum maculatum, O xalis acetosella, Blechnum spicant (spores) or Danthonia decumbens in the s eed bank was favoured by the coniferous plantations. However, most of the f ield layer species were not found in the seed bank. As the typical woodland species, which do not have a persistent seed bank, are the first ones to d isappear from vegetation in coniferous plantations, future management plans should aim to maintain a balance between plantations and natural woodlands and the frequency of cutting, in order to maintain local species diversity . (C) 2000 Elsevier Science B.V. All rights reserved.