Floristic composition of established vegetation and the soil seed bank in pasture communities under different traditional management regimes.

摘要

The floristic composition of the established vegetation and the soil seed bank in seven herbaceous communities under different traditional (hay meadow) management regimes were compared in the Valdeon valley (Picos de Europa, Spain), a valley chosenfor study because of its high diversity and non-dominance of any single species which have become increasingly rare in Western Europe as a result of changes in agriculture practices. Although the biological richness in this valley is well known, few studies have been made of the effects of different traditional management regimes on the floristic soil seed bank composition of these grasslands. The aim of this study was to examine the influence of traditional management regimes on the floristic composition of the established vegetation and soil seed bank determining which species groups are most represented in each case to increase scientific information about these communities that every day are more scarce in Western Europe because of intensive management (generally due to fertilizer application to increase production) and abandonment of the traditional methods of management with a profound modification of the agrarian structure. An indirect germination method was used to study the seed bank. Soil samples were put into a germination chamber, 119 species of the vegetation and 104 of the seed bank were identified, 54 species being common to both. Results were analysed using Correspondence Analysis (CA), samples and species on the above-ground flora being ordered in the first two axes in well-defined groups: limestone and siliceous pastures, formerly-cultivated land and hay meadow. In the case of the below-ground seed bank, the manure used as fertilizer in some communities affected principally the concentration of therophytes in the soil and defined the different groups. Sampling time, management and differences between the persistence of seeds of different species in the soil seed bank were responsible for the large differences between the composition of the vegetation and seed bank. Ruderal species, species with persistent seeds and therophytes, which were better represented in the seed bank were responsible for the low correlation between seed bank and vegetation established.