Vegetation recovery of gypsum quarries: short‐term sowing response to different soil treatments

Abstract

Question: How does the sowing of native species under different soil treatments contribute to the recovery of gypsum habitats affected by quarrying in Mediterranean environments? \ud \ud Location: Mediterranean gypsum outcrops in Granada (SE Spain; 37 degrees 2' N, 3 degrees 45' W). \ud \ud Methods: We conducted an experimental sowing of native perennial species from gypsum habitats (both gypsophiles and gypsovags) considering two factors: bedding materials and surface treatments. For bedding material we used: gypsum spoil, topsoil addition on gypsum spoil, raw gypsum and topsoil removal. The surface treatments were: control, sowing, sowing plus organic matter and sowing plus an organic blanket. There were five replicates per combination treatment (80 plots in total, of 25 m (2) each). The sowing was performed in Nov 2009. All subplots were monitored to estimate density, richness, survival, growth of seedlings and herbaceous biomass, in two monitoring periods (Jul and Oct). \ud \ud Results: No gypsophiles or gypsovags were found in the control plots (no sowing or surface treatment), and therefore natural succession proved ineffective in the first year. In contrast, sowing was very satisfactory, especially on gypsum spoil, where mean density was of more than 15 individuals m(-2). This result is noteworthy as this material remains after the end of gypsum mining activity. Spreading topsoil over gypsum spoil proved to be no more positive, since it provided not only seeds of target species but also of competitor species. Also, with regard to herbaceous species, this treatment produced a highly significant increase of biomass. The organic blanket increased plant density, whereas the addition of organicmatter had significant positive effects on survival and growth of the seedlings. The global high survival rate is remarkable, especially for the gypsum spoil treatment. \ud \ud Conclusions: We highlight the importance of implementing recovery measures in gypsum habitats. An appropriate selection of seed mixture and density, as well as the use of gypsum spoil (the most favourable bedding material, according the results), is sufficient to ensure presence of the key species. Both technical solutions tested, organic blanket installation and organic matter addition, improved the results in terms of density, survival and growth of the seedlings

Does gypsum influence seed germination?

“…In this sense, the role of gypsum solutions at specific concentrations would aid seed germination of some species, being useful to select appropriate conditions to promote seedling production for restoration purposes. In particular, gypsum has been found of key importance when preparing the substrate on which to perform sowings for recovery gypsum habitats (Ballesteros et al, 2012).…”

Rapid revegetation by sowing seed mixtures of shrub and herbaceous species

“…Competition may also exist for nutrition or light, but the relationship differs among different species (Denslow et al, 2006;Mendoza-Hernández et al, 2014). Research indicated a very comprehensive relationship between different coexisting species; not only negative but also positive relationships were shown in different studies (Harmer et al, 2011, Ballesteros et al, 2012Zhang et al, 2013;Oliveira et al, 2014).…”

“…In abandoned quarries or surface mines, recolonization of plants is very difficult (Ballesteros et al, 2012) because of the destruction of natural soil structure and seed bank, as well as the limitation of nutrition and water (Jim, 2001;Haritash et al, 2007). Even though technical restoration can accelerate succession, it takes decades to achieve a complex self-sustainable ecosystem (Zhang et al, 2013).…”

Enhancing seedling production of native species to restore gypsum habitats

“…However, gypsum habitats are 58 often impacted by human disturbances such as quarrying, ploughing or grazing (AlHarthi, 2001;Mota et al, 2004;Pulido-Bosch et al, 2004;Pueyo and Alados, 2007; 60 Ballesteros et al, 2013). Therefore, recovery plans for these environments need to be addressed, and proactive measures need to be considered (Ballesteros et al, 2012(Ballesteros et al, , 62 2014, because natural succession has proved inefficient over the short term (Mota et al 2003(Mota et al , 2004Dana and Mota, 2006).…”

“…The recovery of gypsum areas has been satisfactorily approached through hydroseeding (Matesanz and Valladares, 2007), sowing (Ballesteros et al, 2012) or 66 planting (Sharma et al, 2001;Blignaut and Milton, 2005;Ballesteros et al, 2014).…”