Successional stages of biological soil crusts and their microstructure variability in Shapotou region (China)

Abstract

In order to investigate succession of biological soil crusts (BSCs) and their microstructure variability, we conducted this work in Shapotou revegetation region at the southeast edge of Tengger Deser. The results showed that BSCs generally succeeded as a pathway of ''Algae crusts, algae-lichen crusts, lichen crusts, lichen-moss crusts and moss crusts''. Occasionally mosses directly occurred on algae crusts, and BSCs succeeded from algae crusts to moss crusts. Crust vertical stratification was a common phenomenon, from top to bottom an inorganic layer, algaedense layer and algae-sparse layer were divided in algae crusts; a thallus layer, rhizoid layer and sub-rhizoid layer in lichen crusts; a ''stem-leaf'' layer, rhizoid layer and subrhizoid layer in moss crusts, respectively. The main crust binding organisms varied from filamental cyanobacteria (dominated by Microcoleus) in algae crusts to lichen rhizoids, free-living cyanobacterial filaments and fungal hyphaes in lichen crusts, and to moss rhizoids and fungal hyphaes in moss crusts. The dominant phototrophic organisms varied from Microcoleus (algae) in algae crusts to Collema (lichens) in lichen crusts, and to Bryum (or Didymodon and Tortula; mosses) in moss crusts. Total phototrophic biomass increased while the free-living algal biomass decreased with the succession of BSCs. In addition, exopolysaccharides and fine particles accumulated in the course of development and succession of BSCs, all of which lead to a gradual increase in crust thickness and porosity, while decrease in the bulk density.

Artificially Accelerating the Reversal of Desertification: Cyanobacterial Inoculation Facilitates the Succession of Vegetation Communities

“…Crust organisms also promoted the conversion of sand into soil by increasing soil nutrients and improving topsoil texture. 6,18 In addition, the increased dust deposition on crust surface also could increase soil organic matters and nutrients. 27 Succession of Vascular Vegetation Communities.…”

“…6,7 On the basis of the different dominant species and developmental levels, BSCs are categorized into different successional stages, in sequence including cyanobacterial crusts, lichen crusts, and moss crusts. 6−8 Cyanobacterial crusts normally represent the primary successional stage, light, flat, and brittle.…”

“…However, they play an important role in facilitating crust succession to later stages due to their ability to improve the surface microenvironments and enhance the probability of colonization and survival of later successional species. 6,9 Therefore, artificially accelerating the formation of cyanobacterial crusts is proposed by many researchers for the reconstruction of soil ecosystem function. 9−11 Several projects to accelerate the formation of cyanobacterial crusts, including inoculating crust slurry and dry-crumbled crusts have been proposed, 12,13 but these technologies are not widely used because of the limited inoculum.…”

Analysis of environmental factors determining development and succession in biological soil crusts

“…BSCs are the complex biological-soil mosaic layers within the top millimeters of soil surface, composed of photoautotrophic cyanobacteria, algae, lichens, mosses and heterotrophic bacteria and micro-fungi (Belnap and Lange, 2001;Hu and Liu, 2003;Lan et al, 2012a). As the special life beings, BSCs play important ecological functions in desert ecosystems, such as effectively reducing soil erosion, promoting soil formation, changing soil water and nutrient cycling (Hu et al, 2002;Acea et al, 2003;Lan et al, 2010a).…”

“…Collectively BSCs perform significant ecosystem services, however, the different crust developmental levels or successional stages still affect those services. At present, based on the difference of dominant organisms, BSCs are generally categorized into three different successional stages along with the developmental sequence, including: cyanobacterial, lichen and moss crusts (Housman et al, 2006;Su et al, 2009;Wu et al, 2011;Lan et al, 2012a).…”