| Biological soil crusts serve as a vanguard for improving the ecological environment in arid, semi-arid desertification areas. It is a good indicator of the improvement status which the local ecological environment is undertaking. In desert areas, water condition is a key factor to restrict the ecological environment. Biological crusts play an important role in local vegetation succession due to their abilities to conserve and maintain moisture as their chief ecological protection functions. This study was completed in Yanchi, Gaoshawo in Ningxia Hui Autonomous Region and Dengkou in the Inner Mongolia Autonomous Region from 2010 to 2013. Through field investigation and laboratory experiment, vegetation community characteristics and diversity in desert areas were researched, and characteristics of biological crust thickness stage were analyzed by measuring chemical properties of biological crusts and the lower soil, and then effects of biological soil crusts on water infiltration and evaporation were reached to find the relationship between vascular vegetations and biological soil crusts in desertification area. The major results show that:(1) Study on biodiversity in different desertification ecosystem areas results show that:In Mu Us Desert, there were 13 plant species which belong to 6 families and 11 generas. Artemisia ordosica was the dominant species in Artemisia ordosica communities. Hedysarum Scoparium and Hedysarum Mongolicum were the dominant species in Hedysarum Scoparium and Hedysarum Mongolicum communities, respectively. Species composition and diversity characteristics of Artemisia ordosica communities were better than Hedysarum Scoparium and Hedysarum Mongolicum communities’. The dominant communities were Artemisia ordosica communities in local area.In Ulan Buh Desert, there were 12 plant species which belong to 7 families and 11 generas. Artemisia ordosica was the dominant species in Artemisia ordosica communities. Tamarix chinensis was the dominant species in Tamarix chinensis communities. The species composition and diversity characteristics of Tamarix chinensis communities were better than Artemisia ordosica communities’. The Artemisia ordosica communities were gradually to the Tamarix chinensis communities succession in local area.(2) Study on the distributionof biological soil crusts in different desertification ecosystem areas results show that:In Mu Us Desert and Ulan Buh Desert, biological soil crusts types can be divided into algae, lichen and moss crusts. The dominant species were Microcoleus vaginatus, Collema tenax and Byum argenteum, respectively. In Mu Us Dssert, the dominant species in plant cover and the community both were the lichen crusts in Mu Us Desert; And in Ulan Buh Desert, the dominant species were linchen crusts and algae crusts in plant cover and community, respectively. Biological crust thickness decreases with increasing distance roots. The biological soil crust thickness distribution is associated with the crown of plants in different directions. Perennial dominant wind direction significantly influenced the distribution of biological crust thickness. Comparing two kinds of desert ecosystem, the coverage and thickness of the biological soil crust in Mu Us Desert were thicker.(3) Study on the physicochemical propertiesof biological soil crusts in different desertification ecosystem areas results show that:The relationship among biological soil crusts biomass was manifested as the biological soil crusts biomass of advantage communities was greater in a different desertification ecosystem. Because rain is rich in Yanchi, biological soil crusts biomass was bigger than Dengkou. Compared withalgae and lichen crusts, moss crusts had better bulk density and natural moisture content.The mechanical components were given priority to with sticky powder. The pH value of moss crusts were smaller and the organic matter, total nitrogen, available nutrient contents were higher. The soil enzyme activity is stronger. The physicochemical properties of biological soil crusts of Artemisia ordosica communities in Mu Us Desert and Tamarix chinensis communities in Ulan Buh Desert were better.(4) Study on hydrological characteristics of biological soil crusts in different desertification ecosystem areas results show that:① Biological soil crusts had effects on stopping soil water infiltration. And along with rainfall increasing, the ability of infiltration barrier by biological soil crusts was lower, the wet front increased, the fitting speed of wet front also increased. With the development of biological soil crusts, biological soil crusts thickness increased the ability of infiltration barrier by biological soil crusts increased. In addition, the ability of biological soil crusts blocking water in Mu Us Dssert was better. At the same time, fitting the experimental data of different desertification ecosystem areas with empirical model, the results show that Horton model is better than Kostiakov model and Philip model, which performed water infiltration characteristics of two kinds of desertification areas, and to describe the process of water infiltration rate in the study areas better.② Biological soil crusts on the performance of evaporation were carried out by analyzing the variations of daily and cumulative evaporation. Different types of biological soil crusts and site conditions determine the effect of biological soil crust on the moisture to evaporate when the rainfall is small (< 25mm). Biological soil crust had inhibitory effect on moisture evaporation in the condition of larger precipitation (25 mm);③ The average and quantity of condensation water were increasing with the development of biological soil crusts. And the average and quantity of condensation water in Mu Us Desert was larger than that in in Ulan Buh Desert. The formation of the condensation water was affected by the change of air relative humidity, surface and air temperature, and the difference between atmospheric temperature and surface temperature.Study on biological soil crusts hydrological characteristics and impact factors in a different desertification ecosystem, which can provide theoretical basis and technical support for the effective utilization and biological crusts scientific management for the soil water content in desert area, desertification area of biological crusts become a new way to control soil loss of biological put forward scientific hypotheses, the biological crusts better recovery for the ecosystem area and the ecological environment construction services. |
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