Studies On Flora And Ecology Of Algae In Biological Soil Crust In Gurbantunggut Desert, Xinjiang

The Gurbantunggute Desert (44°11' 46°20'N, 84°31' 90°00'E) is situated in the center of the Jungger Basin, Xinjiang Uygur Autonomous Region of China, and also the largest fixed and semi-fixeddesert in China with an area of 4.88×10⁴ km² . Its altitude above sea level is 300⁶00 m. The mean annual precipitation is no more than 150 mm and only 70-100 mm in the center of the desert, falling predominantly during spring. Mean annual evaporation is 2606.6 mm. Average temperature is 6¹0'C. The annual accumulative temperature which is higher than 10°C is 3 000⁵ 000°C. Mean atmosphericalhumidity is 50⁶0%.Wind speeds are greatest during late spring, with an average of 11.17 m·s^-1 , andare pre-dominantly in WNW, NW and N directions. Shrubs and arbor community in the area composed of Haloxylon ammodendron, H. persicum and other desert plant develop widely. At the same time, ephemeral and ephemeral-like plants develop at a certain extent due to some snow and rainwater in winter and spring. Furthermore, there is a developed biological soil crust on sand surface of the desert.Biological soil crust is a complex organic integrity of cyanobacteria, green algae, lichens, mosses, fungi, and other bacteria. Biologically, this kind of crust differs a lot from incompact sand in physical, chemical and biological properties. It can stabilize and fertilize soil, prevent erosion by water or wind, and becomes an important biological factor in vegetation succession. As pioneers of desert and semi-desert ecosystem, desert algae play an important role on the formation of desert soil and can increase contents of carbon, nitrogen and phosphorus in the soil of desert. Algae crust can also establish biological basis for emergence of lichen crust, moss crust and even higher plant. But no one have progress systemic study on algae of Gurbantunggut Desert in Jungger Basin, Xinjiang. Therefore, a study on algae of the desert is not only very significent in theory, but also crucial in realism and practice.In the paper, species composition, ecological distribution, seasonal change of algae and disturbance of desert road to algae of biological crust were studied in detail by field sampling, laboratory culturing, species identification and physiological experiment. At the base of culturing and species composition, Chlorococcum humicola, Anabaena sp., Calothrix sp., Scytonema sp.and Microcolus vaginatus were separated and purificated. Chlorococcwn humicola and Anabaena sp. were further cultured physiologically.The main results follow as:1. Species diversity of algae in Gurbantunggut Desert is higher than that in Shapotou area in Tengger Desert and Lanzhou northern Hill. There are 148 species in the desert, belonging to 56 genera, 23 families and 4 divisions. Four divisions are cyanophytes, chlorophytes diatoms and euglenoids, in which 92 species are cyanophytes, 27 species are chlorophytesgreen algae, 23 species are diatoms and 6 species are euglenoids. Blue-green algae account for 62.16% of total species. Filamentous algae are dominant in Cyanophyta accounting for 62.88%. Green algae are mainly unicellular and spherical species. Fragilaria sp., Navicula Bory. and Hantzschia garun. are dominant in Baeillariophyta.2. In the study area, dominant families and dominant genus are few, but scant families and scant genus more correspondingly. Dominant families are Oscillatoriaceae and Chroococcacals. Dominant genus are Oscillatoria Vauch.(27 species), Lyngbya Ag.(10 species), Chroococcus Nag.(9 species), Navicula Bory.(9 species), Synechococcus Nag.(7 species) and Chlamydomonas Her.(7 species), hi the area, dominant species of algae are Microcolus vaginatus, Synechococcus aeruginosus, Chroococcus westii, Oscillatoria tenuis and Chlorococcum humicola, which distribute in all the areas that exist algae crust.3. Species diversity and community composition of algae are different in varions areas of the desert. As for the species diversity, algae species of the central desert is the most, the northern desert and southern desert the second, and the eastern and western desert decrease obviously. With regard to community composition, algae are all composed of cyanobacteria, chlorophytes, diotoms and euqlenophytes. Cyanobacteria is dominant evidently in all different areas of desert. And species diversity of it change evidently. The changing tendency is the same as the whole algae community. Chlorophytes, diotoms and euqlenophytes are not dominant in algae community of different areas of the desert.4. In different locations of sand dunes, species diversity of algae was different. The number of algae species is the most in inter dune, the second the windward of sand dune, the third the leeward of sand dune and the least the top of sand dune. Number and species composition of algae exist some differences in different layers. The tendency of biomass of algae varies in different locations of sand dunes in the desert. The biomass of algae in the windward of sand dune is the most, the more the interdune, the leeward the third and the top the least. In the vertical distribution, algal biomass dramatically decreased with the soil depth from the surface to lower levels.5. The difference of algae in spring and summer is the biomass. The biomass in spring is lower obviously than that in summer. But species diversity in spring and summer change little, and the numberis 79 species in spring and 73 species in summer. Species composition in the two seasons is the same on the whole.6. In the study area, the disturbance of desert road to species diversity and biomass of algae is remarkable. The results of ANOVA show that the influence of desert road to the number of algae is highly significent (p = 0.007281). And the influence of desert road to the biomass of algae in biological crust is at the significance level of p < 0.05 (p = 0.035944).7. At the base of culturing, the influence of K+, Ca2+, Mg2+, pH, illumination and temperature to Chlorococcum humicola and Anabaena sp. was studied primarily. The results of ANOVA indicate that the influence of pH and temperature to Chlorococcum humicola is at high significance of p < 0.01, Ca2+ and Mg2+ at significance level of 0.05, K+ is not significant. With regard to Anabaena sp., the influence of Mg2+ and pH is highly significant, K+ and Ca2+ is at significance level, illumination not significant.In conclusion, the paper will provide basic data and theoretic support for selecting dominant algae species and their tie-in model which adapt to their surroundings. The study can offer the first-hand data to future study of algae in biological crust. And this can establish firm foundation for got-up culture of desert algae and technical system of their field implantation.