The effect of evergreen and deciduous coniferous plantations on the field layer and seed bank of native woodlands

Vegetation and seed bank changes due to the replacement of a native woodland 29 yr ago by coniferous plantations (evergreen coniferous Pinus radiata and deciduous coniferous Larix kaempferi) were studied in a replicated experiment in the Basque Country, northern Spain. In the vegetation the species richness was lower in both coniferous plantations than in the native woodland but there was no significant difference in species richness between the two coniferous plantations. The highest similarity between the vegetation and the seed bank was in the P. radiata plantations (0.51). There was higher vegetation similarity between the native woodland and the larch plantation (0.65) than that with the pine plantation (0.58). Seed bank species richness was higher in the arch plantation than in the native woodland but species richness in the seed bank did not differ between the coniferous plantations. The seed bank showed no difference in the species similarity between the plantations and the native woodland. This was mainly due to the similarity between the broad ranged species. In the coniferous plantations the vegetation diversity was lower than in the native woodland; however, in the seed bank the diversity was higher. Coniferous plantations affected mainly the shade-tolerant and shade-intolerant vernals (Caltha palustris, Galium odoratum, Heleborus viridis and Saxifiaga hirsuta), which disappeared from the field layer of plantations while the shade-intolerant not vernals were favoured by the plantations (Blackstonia perfoliata, Danthonia decumbens, Deschampsia flexuosa, Hypericum androsaemum, Holcus lanatus, Lotus corniculatus and Plantago lanceolata). There was no significant difference in vegetation or seed bank between the two types of coniferous plantations.