Central role of bedding materials for gypsum-quarry restoration: An experimental planting of gypsophile species

The loss of the original soil and mineral resources caused by quarrying activities represents a major challenge for the restoration of singular flora associated with specific substrates. In particular, the rare and original gypsum flora is severely affected by quarrying, and identifying the best measures to recover it is decisive for its conservation. In this paper, we evaluate the efficacy that planting with several contrasting bedding-materials has for the recovery of three native gypsophile species in gypsum habitats affected by quarrying. With this aim, in a affected gypsum area in SE Spain, we experimentally planted one-year-old nursery-grown plants of Helianthemum squamatum, Lepidium subulatum, and Ononis tridentata subsp. crassifolia, employing four bedding materials potentially useful for restoration: raw gypsum, gypsum spoil, topsoil on gypsum spoil, and marls. Plant performance was evaluated in terms of survival, growth, and the production of flowers, fruits, and seeds. High survival was achieved in all the treatments, demonstrating the excellent response of these species to planting. However, bedding materials had a significant effect on plant performance, with raw gypsum and gypsum spoil being the options that most benefited growth and production (in terms of flowers, fruits, and seeds). Remarkable results were achieved in raw gypsum, although gypsum spoil appears to be the most reasonable option for restoration, given its low cost, wide availability, and potential to recover disturbed gypsum environments. By contrast, common measures such as the use of topsoil should not be routinely recommended for the recovery of gypsum vegetation. Hence, our study shows the importance of identifying the most appropriate measures when specialized flora is the object of restoration and thus will contribute to the development of strategies for the conservation of gypsum habitats affected by quarrying.