Abstract:

The study area, Shapotou district (37°27′N, 104°57′E) of Ningxia Hui Autonomous Region is situated in the southeastern fringe of the Tengger Desert of China. A study of species identification, coverage and biomass in the soil microbiotic crusts of fixed sand dunes was conducted in Shapotou district, from which we found two families, seven genera and sixteen species of mosses. Didymodon constrictus (Mitt.) Saito and D. tectorum (C. Muell.) Saito were reduced to synonymy of D. vinealis (Brid.) Zand. by Zander and Redfearn. Crossidium chloronotos (Brid.) Limpr., Crossidium aberrans Holz. & Bartr. Aloina obliquifolia (C. Muell.) Broth. and Tortula atrovirens (Sm.) lindb. are new to Shapotou district. Bryum argenteum is an eurytopic species that survives on all kinds of habitat, and is the dominant component that forms moss synusia. The community of Didymodon vinealis, D. rigidulus Hedw. var. ditrichoides and Syntrichia bidentata are found on hillocks and are randomly distributed in crusts. Diversity of species is the highest in this area in the natural fixed dunes, with sixteen species, followed by five species of mosses (31.3%) in the fixed dunes of 1956, four species of mosses (25.0%) in the fixed dunes of 1964, and only two species of mosses (12.5%) in the fixed dunes of 1981. The total coverage of mosses and algae increased with the fixed-sand time. In different ages, the coverage of mosses and algae exist in an equal distance gradient, while in the fixed dunes they exist along the slope with the coverage of mosses decreasing as that of algae increased. A determination of biomass and binding-sand quantity of the dominant species—Bryum argenteum showed that its biomass (944.03 kg·hm-2) and binding-sand (3.925×104 kg·hm-2) quantity increased when the fixed sand time prolonged in moss crusts of the fixed dunes of 1950s. While the rate of binding-sand of Bryum argenteum decreased, its saturated water absorption had a positive correlation with biomass of 7.06×103 kg·hm-2. Therefore the results indicate that the moss crusts had a strong ability to absorb and reserve water, which is of ecological significance in arid desert region.