Micro‐geomorphology determines community structure of biological soil crusts at small scales

Abstract

Biological soil crusts (BSCs) are ubiquitous communities of diminutive organisms such as cyanobacteria, green algae, lichens, mosses and others associated closely with particles of surface soil, forming a cohesive thin horizontal layer. The ecological roles of BSCs affecting soil nutrient cycling, stability and hydrological processes, infl uencing the germination and establishment of vascular plants, and serving as habitats for numerous arthropods and microorganism have been well documented. We tested the hypothesis that micro-geomorphological features determine the spatial distribution of BSCs by reallocating related abiotic resources at small-and medium-scales in the Tengger Desert. Our results showed that higher soil pH and higher total potassium content in topsoil positively correlated with the colonization of cyanobacteria and algae in the earliest successional stages of BSCs, while increasing dust deposition onto the topsoil enhanced the development of lichen and mosses in the later stages of BSCs. Increasing soil moisture raised the proportion of mosses and lichen in BSCs, this will possibly change the ecological functions of BSCs, such as nitrogen-fi xation by cyanobacteria, due to the conversion from a complex to relative simple type of BSC. Micro-geomorphology has created various habitats at a small-scale affecting colonization and development of cryptogams. This paper considers the contribution of micro-geomorphology to biodiversity in the extreme arid desert systems.

Review of the ecohydrological processes and feedback mechanisms controlling sand-binding vegetation systems in sandy desert regions of China

“…After 42 years, the whole layer had almost no available soil water and SWC was highest at 0.1 m depth due to the difference in soil texture between sand and BSCs [61,62]. The different sand-binding dune locations and the variation in the types of BSC covering them led to variability in SWC in the top soil layers [63]. SWC increased in the hollows and on the leeward slopes and windward slopes but the variability in SWC in the hollows was lower than in the soil on the leeward and windward slopes.…”

“…With regards to vegetation functional group composition, the sparsely covered sand-binding shrubs remained but were joined by an increasing number of C 4 plants and cryptogams [63]. C 4 plants diversified the ways that plants used water in the desert and cryptogams became an important resource and provider of soil carbon in the sand-binding areas [84,85].…”

“…The BSC development was an important feature of desert/sandy vegetation and distinguished it from other vegetation types. Li et al [63] discussed how BSC cryptogam diversity was maintained in arid areas and thought that small scale changes in water levels caused by complex micro-geomorphological processes was the key factor behind maintaining diversity and small scale changes in soil physicochemical and biological properties, especially soil texture, determined species diversity and group differences. At a regional scale, precipitation gradients determined BSC species distribution and coverage.…”

“…For instance, Horqin and Mu's sandlands, with more than 300 mm of annual precipitation were suitable for BSC development that was dominated by moss. In stabilized sand dunes with less than 200 mm of annual precipitation, lichen developed as the dominant crust species and cyanobacteria was the dominant crust species in disturbed desert areas [63].…”

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

“…1). The climate and vegetation conditions in those regions are listed in Table 1, in which all the data are cited from the reports of Hu and Liu (2003), Li et al (2004) Xie et al (2007), Jia et al (2008), Rao et al (2009), Lan et al (2010a and Li et al (2010).…”