The Study Of Cultivation And Key Ecological Functions Of Artificial Cyanobacteria Crust In Cropland In The Loess Plateau Region

Due to the loose surface and low vegetation coverage in winter and spring,the cropland soil in the Loess Plateau region is seriously eroded by wind.The wide application of artificial cyanobacteria crust technology in the prevention and control of soil wind erosion in desertification areas provides a new idea for the prevention and control of cropland soil wind erosion in the Loess Plateau region.However,compared with the desert,the wind erosion of cropland soil occurs in a relatively concentrated time,so the artificial cyanobacteria crust needs to be formed in a short time.In addition,the texture of cropland soil and the climatic conditions during inoculation are also very different from those in desertification areas.Therefore,it is necessary to clarify whether it is feasible to inoculate cyanobacteria crust in cropland,the specific inoculation and culture methods,and the possible key ecological effects of artificial cyanobacteria crust,such as the impact on soil moisture.Especially in arid and semi-arid areas,precipitation infiltration is not only related to cropland soil productivity,but also a key factor affecting soil water erosion.For this reason,in this paper,the optimum inoculation concentration and water methods for the formation and development of artificial cyanobacteria crusts in cropland were studied by combining indoor experiments and field experiments.Cyanobacteria species separated from natural biological crusts in cropland in the Loess Plateau region were used as experimental materials.At the same time,the prevention and control effect of wind erosion of artificial cyanobacteria crust and its influence on soil water circulation in cropland were clarified.This study explored the possibility of using artificial cyanobacteria crust technology to prevent cropland soil wind erosion,which provided a new idea for cropland sustainable development and environmental management in the Loess Plateau region.The results are as follows:（1）Inoculation of soil cyanobacteria can promote the formation and development of soil cyanobacteria crusts,and inoculation concentration and watering methods significantly affect the formation and development of artificial cyanobacteria crusts.The optimal initial inoculation concentration is 6.0μg·cm^-2(i.e.0.06 g·m^-2)（based on chlorophyll a content of the soil）and the watering method is 3 mm per day.Under indoor conditions,when the inoculation concentration is 6.0μg·cm^-2（based on chlorophyll a content）and the watering method is 3 mm/d,the artificial cyanobacteria crusts can be formed on the 10th day after inoculation,with coverage of about 80%,biomass of about 14.00μg·cm^-2 and thickness of about 3.66 mm.In the field experiment,on the 9th day after inoculation,cyanobacteria crusts began to form on the soil surface,and on the 18th day after inoculation,stable dark brown cyanobacteria crusts were formed,with a coverage of about 56.13%,a thickness of about3.74 mm,and a biomass of 22.21μg·cm^-2,which was 795.56%higher than that without inoculation.（2）Artificial cyanobacteria crusts can prevent and control cropland soil wind erosion.The wind tunnel experiment showed that the artificial cyanobacteria crust inoculated indoors can completely control soil wind erosion at the wind speed of 13 m·s^-1.The artificial cyanobacteria crust inoculated in the field has not been eroded by wind after a wind erosion season.（3）Artificial cyanobacteria crusts significantly reduced the soil permeability of cropland.Artificial cyanobacteria crust at the early stage significantly reduced the saturated hydraulic conductivity of cropland soil.The saturated hydraulic conductivity of 0～5 cm soil layer covered with artificial cyanobacteria crusts at the early stage is 0.08 mm·min^-1,which is 63.64%lower than that of bare soil.The early stage of artificial cyanobacteria crust has no effect on soil water infiltration parameters in cropland.In the later stage of artificial cyanobacteria crusts,the saturated hydraulic conductivity of 0～5 cm soil layer under moss crusts and cyanobacteria crusts was 0.28 and 0.47mm·min^-1,respectively,which decreased by 55.14%and 23.54%compared with bare soil.The stable infiltration rate,average infiltration rate and cumulative infiltration amount of cropland soil covered with moss crust were 51.11%,47.71%and 46.50%lower than those of bare soil.（4）Artificial cyanobacteria crust has no significant effect on soil moisture evaporation in cropland.At the early stages of artificial cyanobacteria crusts,the evaporation of cropland soil at atmospheric evaporation control stage,soil hydraulic conductivity control stage and water vapor diffusion stage and the soil cumulative evaporation were 20.72 mm,8.69 mm,4.96mm and 34.37 mm,respectively,and there was no significant difference between them and the soil without crusts.In the later stage of artificial cyanobacteria crusts,the evaporation of cropland soil at atmospheric evaporation control stage,soil hydraulic conductivity control stage and water vapor diffusion stage and the soil cumulative evaporation of moss crust soil were 23.42 mm,11.68 mm,5.79 mm and 40.89 mm,respectively,while those of cyanobacteria crust soil was 24.57 mm,10.70 mm,5.53 mm and 40.80 mm,respectively,and there was no significant difference between crusts soil and soil without crusts.To sum up,the application of artificial cyanobacteria crust technology can promote the formation and development of cyanobacteria crust in cropland on the Loess Plateau,and the formed artificial cyanobacteria crust has certain wind erosion prevention effect.Artificial cyanobacteria crust has no significant negative effect on the water evaporation process of cropland soil,but it reduces the permeability of cropland soil,which may affect the effective use of water by crops.