Spontaneous vegetation succession in gravel-sand pits:: A potential for restoration

Vegetation variability, the participation of target and undesirable species, and the role of local species pool were studied in the course of spontaneous succession in disused gravel-sand pits. The study was conducted in various regions of the Czech Republic, Central Europe. The regions represented either agrarian lowlands with a relatively warm and dry climate or mostly woodland uplands with a relatively cold and wet climate. The gravel-sand pits (36) comprised stages of different age from 1 to 75 years since abandonment. Altogether, 224 vegetation samples were recorded with species cover (%) visually estimated. Species affinity to different vegetation types was assessed in each sample based on the species cover. 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 broader surroundings, were evaluated as well as the participation of target (grassland, woodland, and wetland) and undesirable (ruderal, alien) species. Ordination analyses showed that vegetation succession led to target grassland, wetland, or woodland vegetation depending on local site factors, especially moisture and the presence of (semi)natural vegetation in the surroundings (local species pool). Restoration of target vegetation in disused gravel-sand pits by processes of spontaneous succession can be possible and successful in about 25 years, especially if (semi)natural vegetation exists in the surroundings. The invasion of the alien tree Robinia pseudacacia must be taken into consideration within the dry sites in lowlands.