Biomass measuring techniques of soil algae have long been not uniform and have serious practical errors in each. This has
severely retarded the research development of this region. In this study, we collected desert algal crusts of different developmental stages (42, 34, 17, 8, 4 aged) and topsoil of unconsolidated sand located in Shapotou, Zhongwei County, in Ningxia Autonomous Region. We conducted direct counts by using acridine orange and 4,6-diamidino-2-phenylindole dyes under fluorescence microscope; dilution plate techniques by a series of dilution gradients incubated on BBM, BG11, BHB-D1 and Chu'10 agar culture media;
biovolume method by translation of both direct counts and plate counts results into volume for each species of algae. By comparison we put forward a relative standard method to quantified algal
biomass in species level, namely biovolume techniques. The detailed biovolume technique is: (1) Sampling should be much finer in depths. Normally the vertical samplings are done at serial sections of 0～5, 5～15, 15～50, 50～150, 150～200mm in depth respectively. In the laboratory, sections of those blocks were firstly scraped clean with a sterile scalpel, then cut into 0～1, 1～2, 2～5, 5～10, 10～15, 15～20, 20～25, 25～50, 50～100, 100～150 and 150～200 mm blocks, whereas clay kinds soil into 0～5, 5～15, 15～50, 50～150, 150～200 mm blocks. (2) Samples should be ground, diluted, shook and dispersed as possibly as it can before culture;(3) The average volume of each species was measured by direct observation (species can be identified without culture) and solid culture observation (species can be identified only under culture condition); (4) Many kinds of culture media and 3～4 replications should be used for each media; (5) Natural community structure and percentage of dominant species should be determined under direct observation;( 6) Volume calculation should include both natural and culture community structure. Biomass was expressed as volume per gram dry soil. According to this method the average biovolume was 5.99～8.58 mm3·g -1 dry soil in the algal crusts of non-irrigation area of Shapotou, and 1.28 mm3·g -1 dry soil in irrigation area. The maximal biovolume was exhibited in August with the highest precipitation; the minimal value in February with the lowest air temperature. Additionally 6 microclimates factors (wind speed, air and surface temperature, evaporation, precipitation and humidity) and 27 soil microenvironment parameters (total N, P, K, rapidly available N, P, K, C/N, organic matter, moisture, pH, electric conductivity, Ca 2+, Mg 2+, SO 4 2+, CI-, Mn, V, Zn, Cu, Fe, Co, coarse sand grains, fine sand grains, coarse silt, fine silt and coarse clay particles) associated with biovolume were considered. Stepwise multiple regression indicated that biovolume was positively correlated with the amount of local precipitation, total K 2O, soil hydrolyzable nitrogen, Fe 3+ and coarse silt, while negatively correlated with pH, organic matter, Cu and Zn. Meanwhile it was affected by trace element Co. This regression results were compared with other associated research as well.