Spontaneous vegetation succession in disused gravel-sand pits:: Role of local site and landscape factors

Questions: What is the variability of succession over a large geographical area? What is the relative importance of (1) local site factors and (2) landscape factors in determining spontaneous veactation succession? Location: Various regions of the Czech Republic, Central Europe. The regions represent two categories characterized by agrarian lowlands. with a relatively warm and dry climate, and predominant woodland uplands with a relatively cold and wet climate. Methods: Gravel-sand pits ranged in age from 1-75 years since abandonment. Three types of sites were distinguished: dry, wet and hydric in shallow flooded sites. Vegetation releves were recorded with species cover (%) visually estimated using the space-for-time substitution approach. Local site factors, such as water table and soil characteristics, and landscape characteristics, namely climatic parameters, presence of nearby (semi-) natural plant communities and main land cover categories in the wider surroundings, were evaluated. Results: Ordination analyses showed that water table was the most important local site factor influencing the course of spontaneous vegetation succession. Succession was further significantly influenced by soil texture, pH, macroclimate, the presence of some nearby (semi-) natural communities and some land cover categories in the wider surroundings. Spontaneous vegetation succession led to the formation of either shrubby grassland, deciduous woodland, Alnus and Salix carrs, and tall sedge or reed and Typha beds in later stages depending predominantly on the site moisture conditions. Conclusions: Although the water table was the most influential on the course of vegetation succession, the landscape factors together explained more vegetation variability (44%) than local site factors (23%).