Interaction Of Biological Soil Crust And Environmental Water In Kubuqi Sandy Land, Inner Mongolia

Ecological researchers very attached importance to the ecological rolesof the biological soil crusts in sandy environment, because it could effect soilparticle stability and erosion, soil-plant-water relations, water infiltration,evaporation, runoff and condensation in soil, and plants establishment andcover, etc. The study area was located in Kubuqi desert, and Well-developedbiological crusts formed in its surface were taken as the research objects.Based on field species identification, laboratory analyses of physical andchemical properties and dynamic investigations, this paper was conducted tostudy on the diversity composition of vegetation plots and biological soilcrusts in fixed dune, the effects of biological soil crusts on soil particle, soilbulk density and soil moisture, and the mutual influence relationship withbiological soil crust and environmental water. The results were as follows:1. Compared with no crust, the content of soil clay and silt wereincreased, and the content of sand was decreased under biological soil crust.The clay content of moss crust was increased2.798%, the clay content ofalgal crusts was increased2.007%, and the silt content of moss crusts wasincreased0.974%, the silt content of algae crusts was increased0.86%. Soilbulk density of biological soil crust was decreased, showing moss crust<algaecrust<no crust. And the soil bulk density was increased with the increase ofthe depth of the soil. Water content on soil with biological soil crust differedwith the increase of soil depth, it was increased between the soil depths of0-10cm and decreased between the depths of10-30cm, and the value ofincreasing or decreasing by moss crust was larger than it by algae crust.2. The diurnal variation curve of photosynthesis of biological soil crustwas a single peak; the minimum peak was at14:00pm. The diurnal variationcurve of respiration of biological soil crust was bimodal; the maximum peaks were at10:00am and22:00pm. The value of photosynthetic Yield orrespiratory rate indicated that moss crust>algae crust. And after rain the valuewas greater than the value before rain. The moss crust value was increased0.21mm and at highly significant level (p<0.01), the algae crust value wasincreased0.08mm and at significant level (p<0.05). Increase of soil watercontent can enhance the photosynthesis and respiration of biological soilcrusts.3. The diurnal variation of soil moisture before rainfall and after rainfallshowed: the soil moisture and water retention in0-5cm reflected mosscrust>algae crust>no crust, while they in20-30cm reflected moss crust<algaecrust<no crust. The regulation of biological soil crust on the soil moisture isgreater than no crust, and even the driving force of moss crust has beenextended to30cm soil depth. Biological soil crusts crust slowed theinfiltration rate of soil moisture, extended the residence time of water in thesoil surface, and increased the saturated holding capacity of soil water.4. Analysis of evaporation intensity showed: the average of moss crustswas0.078mm, the average of algae crusts was0.163mm, the average of nocrusts was0.216mm,demonstrating that moss crust <algae crust<no crust, butthe changes of evaporation curve were also unequivalent between the soilwith crust and no crust, that depending on the soil water content. Soilevaporation intensity was stronger than no crust while the soil water contentwas higher; soil evaporation intensity was weaker while the soil water contentwas lower. Biological soil crust significantly changed evaporation process ofsoil. The influence mechanism of biological soil crust on soil evaporation wasnot simple promotion or inhibition; it showed difference with different timeperiods. When soil water content was higher, soil water evaporation on soilwith biological soil crusts was higher compared to soil without crust; however,when soil was gradually drying, biological soil crusts sealed the soil surface,restrained water in the soil and reduced soil evaporation. Viewing thecumulative soil evaporation, biological soil crusts inhibited soil evaporation.5. The mean of condensation water content was1.916mm with moss crusts, was1.496mm with algae crusts and was1.207mm with no crusts,indicating the mount of condensation water was that moss crust>algaecrust>no crust. Diurnal variation curve of the condensate water was a singlepeak in different types of crusts, and the maximum peak was at between6:00am and7:00am. The formation of condensation water was directly affectedby the atmospheric relative humidity and temperature. It was positivelycorrelated with atmospheric relative humidity, and it was negativelycorrelated with temperature.