Long-term changes (1982–2010) in the bryodiversity of Spanish beech forests assessed by means of Ellenberg indicator values of temperature, nitrogen, light and pH

The bryodiversity of nine Spanish Fagus sylvatica forests of four different phytosociological associations was re-studied nearly 30 years after initial sampling. Species richness and composition, Jaccard and Sّrensen similarity indexes, and Ellenberg indicator values (E.i.v.) for temperature, nitrogen, light and pH were compared between the two periods of time. Changes were also studied for groups -mosses and liverworts- and habitats -epigeic, epiphytic and epilithic species. Species richness values have not significantly changed in most of the forests, but composition has done, resulting in low similarity values over time. Liverworts and epiphytes were the least sensitive groups to changes. E.i.v. changes showed general trends towards warmer and more nitrophilous, shady and acidic conditions, changes being more consistent in woods located near the limit of survival of beech. The increase in temperature revealed by the E.i.v. has been corroborated with meteorological data. Changes in light conditions under the canopy could be attributed mainly to changes in forestry management. All the forests studied showed a great turnover of species, even though they have different legal protection levels. To our knowledge, all this means that: (a) changes observed in bryodiversity are the consequence of the combination of natural and anthropogenic factors occurring at different scales, (b) the protection of areas or habitats does not prevent them from changing and (c) E.i.v. are a useful tool to detect even subtle changes in protected areas. Protection is not enough; we must have better understanding of ecosystem dynamics in order to establish appropriate conservation policies.