Species diversity, biomass and long-term patterns of biological soil crusts with special focus on Cyanobacteria of the Acacia aneura Mulga Lands of Queensland, Australia
Williams, Wendy J.; Büdel, Burkhard
The Australian Mulga Lands bioregion covers 251,640 km 2 and is characterised by Acacia aneura mulga and Eucalyptus populnea woodlands. Equally important to land managers are the extensive perennial grasslands. Since the late 1800's almost the entire bioregion was settled by pastoralists and grazed by sheep or cattle on large leasehold stations. Well-established cyanobacterial soil crusts are an important part of this semi-arid ecosystem, providing a nutrient-rich layer closely integrated into the soil surface. Crust diversity from twelve Mulga Land sites was 61 taxa, comprising 23 cyanobacteria, 18 chlorolichens, 5 cyanolichens, 6 liverworts, 6 mosses, 2 eukaryotic algae and 1 micro-fungus. Notably the soil crusts at this site and others across the Mulga Lands were dominated by Porphyrosiphon notarisii and the N-fixing Scytonema hofman-bangii. Cyanobacterial diversity was well represented at the study site where diversity accounted for > 50% of the 23 species. Biomass of crusts from the study site ranged between 91-117 mg m -2 chlorophyll a, similar to several records from across Queensland. Morphologically, cyanobacteria frequently appeared stunted in size compared to other records, indicative of frequent droughts and prolonged periods of desiccation. The cyanobacteria from the study site were resilient to drought although recovered at different rates. Porphyrosiphon notarisii tolerated and recovered from drought exceptionally well while Gloeocapsopsis cf. dvorakii was least drought tolerant. Nostoc commune and Microcoleus spp. were abundant in degraded sites or where soil chemistry was more neutral or alkaline. This study illustrated a highly diverse cyanobacterial crust community across the Mulga Lands dominated by drought tolerant cyanobacteria. This paper presents the first taxonomic descriptions based on morphological features of the key terrestrial cyanobacteria found commonly across the Mulga Lands.