Biological soil crusts of the Succulent Karoo: a review§. Issue 3 (10th December 2018)

• Record Type: Journal Article
• Authors: Weber, Bettina; Tamm, Alexandra; Maier, Stefanie; Rodríguez-Caballero, Emilio
• Is Part Of: African journal of range & forage science. Volume 35:Issue 3/4(2018)
• Page Start: 335
• Page End: 350
• Publication Date: 2018-12-10
• Subjects: biodiversity -- climate change -- CO2 gas exchange -- reactive nitrogen compounds -- remote sensing; Range ecology -- Africa -- Periodicals; Range ecology -- South Africa -- Periodicals; Range management -- Africa -- Periodicals; Range management -- South Africa -- Periodicals; Pasture ecology -- Africa -- Periodicals; Pasture ecology -- South Africa -- Periodicals; Pastures -- Management -- Periodicals; Forage plants -- Africa -- Periodicals; 633.202096
• DOI: 10.2989/10220119.2018.1527782
• Languages: English
• ISSNs: 1022-0119

Abstract

Abstract : The Succulent Karoo is characterised by a dense coverage of biological soil crusts (biocrusts) belonging to different types and successional stages. Whereas the Soebatsfontein region hosts cyanobacteria-dominated and minor amounts of lichen- and bryophyte-dominated biocrusts, the Knersvlakte comprises a rich cover of hypolithic crusts growing on the sides and undersides of quartz pebbles. Apart from dominating photosynthesizers used to classify biocrusts, each crust type hosts a rich and specific fungal and bacterial community and also diverse protists. In a remote-sensing mapping approach, soil-inhabiting biocrusts of the Soebatsfontein region covered ∼27% of the surface area, whereas in the Knersvlakte soil-inhabiting biocrusts covered ∼16% and hypolithic biocrusts ∼42% of the region. Combining these data with biomass contents, results suggested that the Knersvlakte, despite somewhat harsher environmental conditions, harboured about 65% more biocrust biomass per surface area. In physiological measurements we observed that biocrusts emit the reactive nitrogen compounds nitric oxide and nitrous acid, showing water pulse-dependent emission patterns. In addition, CO2 gas fixation showed characteristic type-specific patterns depending on climatic conditions. Long-term microclimate measurements along a gradient revealed that forecasted climate and land-use change may be detrimental for biocrusts with potentially adverse effects on soil stability and overall fertility of the Succulent Karoo.