Investigation Of The Spatial Distribution And Multiple Ecological Functions Of The Biological Soil Crusts In Mu Us Sandland

The biological soil crusts are widely distributed in arid and semi-arid ecosystems where the growth of vascular plants are limited,which play important roles in many ecosystem functions including preventing water and soil loss,regulating soil hydrology and promoting nutrient cycling.Understanding the spatial distribution and ecological functions of biological soil crusts is of significance for the scientific management and protection of biological soil crusts and,for the valid assessment of the contribution of biological soil crusts.For getting hold of the growth conditions,spatial distribution and ecological functions of biological soil crusts,this research based on quadrat surveys in 40 sites and long-term monitoring experiment in the typical site in Mu Us Sandland,combined with analysis and measurement in the laboratory,which acquired the local environmental factors,growth factors of biological soil crusts and the data of soil moisture and wind erosion in the monitoring plots.The growth conditions and the spatial distribution of biological soil crusts,the influence of biological soil crusts on soil nutrition,soil moisture and wind erosion were investigated systematically,and the effects of environmental factors on biological soil crusts were analyzed by the structural equation model.The main conclusions are as follows,1)The algae and moss crusts widely contributing in the Mu Us Sandland,the average coverages of algae and moss crusts are 14.1%and 11.3%respectively,the average thicknesses of algae and moss crusts are 4.5 mm and 7.5 mm respectively;the average height of moss crust is 2.0 mm and the average biomass of moss crusts is 2.2 g/cm~2.The coverage of moss crusts appears to an increasing trend from the northwest to southeast,the coverage of algae crusts is higher in the north and decreases from north to south;the biomass of moss crusts increases form the west to the east.2)In the plot scale,the algae crusts and moss crusts within different development phases mostly distribute in the shrubland and the bottom land among the sand dunes where the water conditions are better than surrounding areas;there are almost no biological soil crusts in travelling dune,grassland of desertification,farmland,and other areas like inner city.In the regional scale,the moss crusts are dominant in the southeast and northeast of the frontier area,the algae crusts are dominant in the central and northwest;there are sparse moss or algae crusts in the southwest.The developmental phrase of algae crusts in the central and western region mainly are medium,the algae crusts in the northern,eastern and southern region are able to come up to late phrase;the moss crusts mainly come up to medium and late phrase in the whole area except part of regions in the western.3)The algae and moss crusts are able to increase the contents of organic carbon,total nitrogen and total phosphorus in the crusts and the soil of 5 cm below the crusts,which is benefit for increasing the soil nutrition in this area.The algae crusts can improve the soil moisture of 0-30 cm under Artemisia desertorum Spreng.,and 30-80cm under Caragana korshinskii Kom.and Salix mongolica C.;the moss crusts can increase the soil moisture of 0-80 cm under these 3 shrubs.The algae and moss crusts are able to reduce the soil loss by wind under Artemisia desertorum Spreng.,Caragana korshinskii Kom.and Salix mongolica C.4)The analysis results by the structural equation model reveal that,there is slight correlation among the landform factors represented by slope,slope and elevation,as well as the grazing disturbance,with algae crusts growth,soil factors and plant factors;there is a significant negative correlation between the aridity and plant growth,which means the drought has an inhibiting effect on plant growth;there is no significant negative correlation between the aridity and the growth of algal crust,the drought may has an indirect influence on the growth of algae crusts by restraining plant growth.There is a significant positive correlation between aridity and the growth of moss crusts,the drought may promote the growth of moss crusts by restraining plant growth;the coverage of plants has an negative impact on moss crusts growth;the coverage of plants has insignificant positive influence on the soil of 5 cm under moss crusts,while there is an indistinctive positive correlation between soil condition of 5cm under the moss crusts and moss crusts growth.