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We assessed the diversity and distribution of soil fungal communities associated with biological soil crusts (BSCs) in the southeastern Tengger Desert (China) using 454 pyrosequencing. Soil fungal communities showed high diversity, with 63,427 reads belonging to 478 operational taxonomic units (OTUs). Of these OTUs, 369 belonged to the Ascomycota, 73 to the Basidiomycota, 24 to the Chytridiomycota, one to the Glomeromycota, five to the Mortierellomycotina, and six to unassigned phyla. The most frequent genera were Phoma , Fusarium, Alternaria, Dendryphion, Peyronellaea, Curvularia, Epicoccum, Embellisia and Pleiochaeta . Different BSC sands (algae-crust sand, moss-crust sand and lichen-crust sand) did not harbor significantly different fungal communities. However, the fungal communities in these BSC sands were significantly different from those in non-crusted sands, with members of the Hypocreales and Fusarium being more frequent in the latter. The distribution of soil fungi (measured by Bray-Curtis distance) correlated with abiotic parameters, including total P ( r 2 = 0.9191, P = 0.001), organic C ( r 2 = 0.7237, P = 0.004), total N ( r 2 = 0.7200, P = 0.004), pH ( r 2 = 0.6858, P = 0.002) and electrical conductivity ( r 2 = 0.4723, P = 0.030). The results suggest that BSCs in the Tengger Desert harbor diverse fungal communities that are influenced by abiotic factors. [ABSTRACT FROM AUTHOR]

We examined the influence of sand burial of 0.5-mm and 10-mm depths on micro-fungal communities inhabiting moss-dominated and mixed biocrusts in the vicinity of the Shapotou Research Station in the Tengger Desert, China. The buried communities were compared with those in unburied crusts, as well as with the sandy below-crust and topsoil communities. We isolated 65 fungal species belonging to 43 genera using the soil dilution plate method. Compared to the unburied communities, the buried crust communities were characterized by lower abundance of melanin containing species, especially those with large many-celled conidia, but higher abundance of species producing small light-colored and one-celled conidia, mainly mesophilic Penicillium spp. Sand deposition also caused reduction of isolate density that was more pronounced in the mixed crusts. Diversity characteristics of micro-fungal communities and isolate densities varied in the two crust types in response to the same level of sand burial. This difference between the mixed and moss-dominated crusts was less expressed when the communities had been subjected to the deep sand burial. Below-crust sandy communities showed a more significant decrease both in isolate density and species richness compared to buried crust communities, which was accompanied by the substitution of dominant species – the thermotolerant Aspergillus fumigatus in the subcrust sandy layers instead of melanized species with large multicellular conidia in the crusts. On the whole, the influence of sand burial on crust micro-fungal communities was likely associated with the shielding effect of sand layer which might protect the crust layer from evaporation and UV-radiation. Whereas sand deposition in the crusts partly changed the substrate quality and microclimatic conditions for soil micro-fungi, transition from the crust to the below-crust sandy layer much more substantially altered the environmental situation (mainly in nutrient status, from the comparatively rich organic crust layer to the poor mineral sandy layer) thus leading to the more significant changes in the micro-fungal communities. [ABSTRACT FROM AUTHOR]

Abstract: Wind has extensive effects on biological and ecological performances of organisms throughout the world. However, the responses of desert biological soil crusts to wind are still largely unexplored. Bryum argenteum and Didymodon vinealis are two predominant soil crust mosses that exhibit restricted, contrasting microhabitats with B. argenteum being excluded from higher wind speed microsites in the windward slopes of fixed sand dunes in the Tennger Desert, Northern China. We conducted this study to determine if wind has negative effects on the ecophysiological variables of the two soil crust mosses and whether D. vinealis possesses greater resistance to high wind speed than B. argenteum. The results showed that photosynthesis, respiration, PSII photochemical efficiency, photosynthetic pigments, shoot upgrowth, productivity and regeneration potential of the two soil crust mosses were all drastically inhibited due to the rapid drying, prolonged drought period and unfavorable coupling of moisture and temperature under high wind speed conditions. In addition, D. vinealis displayed stronger resistance to wind than B. argenteum based on all of the aspects mentioned above. Overall, the negative effects of wind on the physiology of soil crust moss and the differential resistance to wind observed in this study suggest that wind is an important determinant regulator influencing ecological micro-distribution patterns of soil crust moss in desert ecosystems. [Copyright &y& Elsevier]

Abstract: Little information is available regarding the responses of biological soil crusts to sand burial in desert ecosystems. Therefore, in this study, we evaluated the effects of sand burial (sand depth of 0, 1, 2, 3 and 4mm) followed by simulated precipitation (1, 3 and 5mm distilled water, sprayed at 2-day intervals) on CO2 exchange and growth by four types of crust collected from a revegetated area of the Tengger Desert (Northern China) in 2007. The results revealed that the respiration rate was significantly decreased and that moss shoot elongation was significantly increased (P <0.001) following burial. Both of these responses may have acted as compensatory mechanisms that favoured the recovery of crust after burial. The burial responses among the four crusts were also compared by measuring the cryptogam cover variations after burial and then computing the speed of emergence and a tolerance index (by standardizing the speed of emergence with a burial ratio of sand burial depth to the initial maximum height of the crust). Among the four crusts evaluated, Bryum argenteum crust showed the fastest speed of emergence (average 11.5% cover week−1) and highest tolerance index (average 0.182), followed by Didymodon vinealis crust (emergence, 11.3% week−1; tolerance, 0.129), Syntrichia caninervis crust (emergence, 7.7% week−1; tolerance, 0.097) and Collema tenax crust (emergence, 4.2% week−1; tolerance, 0.022). This sequence was in agreement with the successional order of these crusts that has been observed in the revegetated area evaluated in this study, which suggests that sand burial is one of the most important factors driving the succession of crusts in desert ecosystems. Furthermore, water played a role in the recovery process, as evidenced by pronounced decreases in dark respiration and increases in photosynthesis, speed of emergence and tolerance index for each crust type, as well as by shoot elongations by three mosses in response to the accretion of water. The restriction of tolerance against sand burial under limited precipitation conditions emphasizes the necessity for sand-binding measures to alleviate the negative effects of sand burial on crusts, which are crucial to preventing revegetated areas from undergoing desertification. [Copyright &y& Elsevier]