Definition: Surface-bound assemblages of microorganisms consolidate soils into mm to cm-thick crusts that occur on arid lands wherever the lack of water restricts the settlement and development of plant cover. To know more about Biological Soil Crusts, please explore the further sub-sections.
Biological soil crusts (BSCs) are also known as cryptogamic or cryptobiotic microbial communities. They are complex microbial communities dominated by cyanobacteria as primary producers that build crust on the top layer of arid lands soils.
- 35% of the total Earth’s continental surface is covered by arid lands, BSC usually cover these areas
- 30 to 350 kg C ha-1 is the annual range of carbon input in BSC
- 1 to 100 kg N ha-1 is the annual range of nitrogen fixation in BSC
- 4th is the position of Microcoleus vaginatus in the World ranking of the most abundant cyanobacteria
- 54 x 1012 g of Carbon is the biomass of microbial primary producers in BSC
In spite of their geographic extent and ecological importance, many aspects of the biology of BSCs remain unknown; this is why we are studying them!
BSC formation, story of a very slow process
- Crusting is initiated by growth of filamentous cyanobacteria (e.g. Microcoleus sp.) during episodic events of available moisture.
- As they grow, these cyanobacteria produce a high amount of slime (extra-polymeric substances) that traps mineral particles.
- This process result in the formation of a pioneer light-crust.
- Once the crust is stabilized other microbes colonize the crust. For instance other cyanobacteria (e.g. Nostoc sp.) forms black colonies on the top of the crust
- Later on, other organisms, such as lichens, eukaryotic microalgae, and mosses, may be integrated as dwellers of the crust.
Restoring Biocrusts
We are currently very interested in using biocrusts to restore native deserts of arid lands. Check out this YouTube video about biocrust restoration, and more here. Biocrusts may be useful in controlling dust and Valley Fever. We do this using our Biocrusts Nursery Facility. You can read more about this facility and our work here: https://www.azcentral.com/in-depth/news/local/arizona-science/2020/12/08/biocrust-could-curb-dust-storms-and-erosion-yet-disappearing/6142802002/?fbclid=IwAR2eIgxkrPckxf8YSiydEVGdK0xFZ4ogfLpnf239qEtigYNiA5xvVv89eNk and here: https://biodesign.asu.edu/news/first-its-kind-microbial-nursery-grand-opening
References:
Garcia-Pichel, F., Lopez-Cores, A., and Nubel, U. (2001) Phylogenetic and morphological diversity of cyanobacteria in soil desert crusts from the Colorado Plateau. Applied and Environmental Microbiology 67: 1902-1920.
Belnap, J., and Lange, O.L. (2001) Biological soil crusts: Structure, function, and management. Spirnger-Verlag. Berlin, 479 p.
Zaady, E., Gutterman, Y., and Boeken, B. (1997) The germination of mucilaginous seed of Plantago coronopus, Reboudia pinnata, and Carrichtera annua on cyanobacterial soil crust from the Nagev Desert. Plant Soil 190: 247-252
Garcia-Pichel, F., and Belnap, J. (1996) Microenvironments and microscale productivity of cyanobacterial desert crust. Journal of Phycology 32: 774-782.
