Abstract
Biocrust communities provide a pallet of ecosystem services, such as soil stabilization, altering of hydrological cycles and primary production, and often are the first colonizers of unvegetated surfaces during succession. Therefore, artificially establishing biocrusts can improve soil properties, for example, by stabilizing bare soil surfaces against erosion or by accumulating nutrients. In this study, the establishment of artificial biocrusts was tested for the restoration of potash tailings piles that result from potash fertilizer production and mostly consist of NaCl. A biocrust cover as primary vegetation could decrease the saline seepage waters by trapping rainwaters, thereby reducing the environmental pollution. In a laboratory experiment, we created a salt gradient by mixing the tailings materials with non-saline dune sand. Surface material of the abandoned potash tailings pile Neuhof-Ellers (NE) and material of the Infiltration Hampering Stratum (IHS) were tested, along with a treatment with bone charplus (BCplus) and sodium alginate. A mixture of 50% (w/w) IHS and dune sand was most successful for the establishment of green biocrust microalgae, based on increased biomass and photosynthetic performance. The chlorophyll a content was negatively correlated with the electrical conductivity (EC), and was significantly increased in the BCplus and sodium alginate treatment, while biocrusts failed to establish on pure tailings piles substrates. The limit of the substrates EC for biocrust establishment was 35 mS cm−1. This limit provides a baseline for future studies that should use BCplus and sodium alginate to increase the success of biocrust establishment on potash tailings piles.
Highlights
Biological soil crusts are often overlooked, but ecologically significant communities found at the soilatmosphere interface
The 50% (w/w) Infiltration Hampering Stratum (IHS) samples with and without additives reached the highest increase from start to end of the experiment, calculated as the relative change of the effective quantum yield ΔY(II) after inoculation vs. end of the experiment (Fig. 5), i.e., photosynthetic performance in these IHS samples increased on average by 79% for 50% (w/w) IHS A− and by 59% for 50% (w/w) IHS A+, The Chl a content was measured at the end of the experiment as a proxy for the biomass of the biocrusts (Fig. 6a)
Green algae were for the first time successfully applied to the artificial induction of biocrusts on saline substrates containing potash tailings pile materials in the laboratory
Summary
Biological soil crusts (biocrusts) are often overlooked, but ecologically significant communities found at the soilatmosphere interface. Biocrusts reduce erosion by wind and water (Belnap and Büdel 2016), and their important role in hydrological processes has been discussed in various studies (Belnap 2006; Bowker et al 2013; Chamizo et al 2016; Gypser et al 2016; Kidron 2016, 2019; Whitney et al 2017; Rodríguez-Caballero et al 2018) In their mostly harsh habitats, biocrust plays an important role in nitrogen (Barger et al 2016) as well as carbon cycles (Sancho et al 2017), thereby accounting for 7% of the global terrestrial net primary production and about 50% of terrestrial biological N fixation (Elbert et al 2012).
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