| Karst rocky desertification is the most prominent regional problem in ecological construction of southern China.The effectiveness of control is one of the main bases to judge the level of ecological civilization construction and sustainable development in this region.The Fifth Plenary Session of the 19th CPC Central Committee required scientific promotion of the comprehensive control of rocky desertification.The influence of biological crusts on soil physical and chemical properties and the study of cultivation technology are important approaches to improve the control of rocky desertification.And it is of great significance to discuss the coupling relationship between biological crust and karst ecological environment and to supplement the control measures of rocky desertification.According to the theories of physical geography,plant functional traits tradeoff,rational disposition,sustainable development and co-evolution of environment,ecosystem structure and function,ecological environment restoration,the coupling relationship between ecological function of biological crusts and soil environment restoration in rocky desertification area,and the establishment of artificial cultivation technology system and other scientific problems and scientific and technological needs.In Guizhou plateau mountainous area,which represents the overall structure of karst ecological environment types in southern China,Bijie Salaxi river with potential slight rocky desertification in plateau mountainous area and Guanling-Zhenfeng Huajiang river are selected as study areas with medium strong rocky desertification in plateau canyon.From 2018 to 2021,through field investigation experiments,artificial cultivation experiments,experimental analysis,comparative analysis,variance analysis,and comprehensive analysis,the whole chain design,integrated deployment and sub module promotion were carried out for the research on the influence of rocky desertification biological crust on soil physical and chemical properties,the basic frontier research and the development of common key technologies.The impact of four biological crusts on the improvement of soil physical and chemical properties was explored and carried out in the laboratory.And the effect of exogenous additives on growth and development of moss crusts were tested in the laboratory.Through synthetically analyze the effects of moss crusts,mixed crusts,lichen crusts and algae crusts on the physical and chemical properties of the soil,and the effects of plant growth regulator,nutrient solution and water retaining agent on plant coverage,plant height and plant density,the improvement mechanism of biological crusts on soil physical and chemical properties was emphasized,the influence mechanism of exogenous additives on artificially cultured biological crusts was revealed,the technology of soil environment improvement and artificial cultivation related to biological crusts of rocky desertification were proposed.All these provide scientific reference for the comprehensive control of rocky desertification.(1)Through the trial experiment in the Bijie Salaxi Demonstration Area,contrast the moss skin plot,mixed skin sample plot(the proportion of moss,lichen and algae was 5:3:2),lichen skin plot,soil physical and chemical indicators of algae crust sample plot,moss skin plot and mixed skin plot>lichen skin plot and alga skin plot.Biological crusts can effectively promote the accumulation of soil elements,and have the greatest impact on the surface soil,and the impact gradually decreases with the deepening of soil layer.In terms of the effects of biological crusts on soil physical and chemical properties,all types of biological crusts have certain improvement effects.The effects of mosses and mixed crusts on soil elements of C,N,P,K was obvious,while the effects of lichen and algae crusts on soil physical and chemical properties are lower than other two types of crusts.Except for soil p H,soil porosity,soil field water holding capacity,soil organic carbon,total nitrogen,available nitrogen,total phosphorus,available phosphorus and available potassium were significantly increased(P<0.05).For example,in the Salaxi Demonstration Area,the soil organic carbon of the sample covered by biological crust increased significantly,with the maximum increase of moss crust was 4.98g·kg-1and the lowest increase of algae crust2.88g·kg-1.In total nitrogen content,the maximum increase of moss crust was0.91g·kg-1,and the minimum increase of algae crust was 0.52g·kg-1.The maximum increase of moss crust was 28.91g·kg-1,and the minimum increase of algae crust was21.01 g·kg-1.In total phosphorus content,the maximum increase of moss crust was0.51g·kg-1,and the minimum increase of algae crust was 0.21g·kg-1.The maximum increase of moss crust was 4.85mg·kg-1 and the minimum increase of algae crust was1.31mg·kg-1 in available phosphorus content.In the content of available potassium,the maximum increase of moss crust was 15.12 mg·kg-1,while the minimum increase of algae crust was 9.12mg·kg-1.(2)Through the experiment in Huajiang Demonstration Area,contrast the moss skin plot,mixed skin sample plot(the proportion of moss,lichen and algae was5:3:2),lichen skin plot,soil physical and chemical indicators of algae crust sample plot,moss skin plot and mixed skin plot>lichen skin plot and alga skin plot.The effect of biological crusts on soil nutrient changes is significant,and the effect on surface soil is the largest,and decreases with the deepening of soil layer.In terms of the effects of biological crusts on soil physical and chemical properties,all types of biological crusts have certain improvement effects.The effects of mosses and mixed crusts on soil elements of C,N,P,K was obvious,while the effects of lichen and algae crusts on soil physical and chemical properties are lower than other two types of crusts.Except for soil p H,soil porosity,soil field water holding capacity,soil organic carbon,total nitrogen,available nitrogen,total phosphorus,available phosphorus and available potassium were significantly increased(P<0.05).For example,in the Huajiang Demonstration Area,the sample of soil organic carbon covered by biological crust increased significantly,with the maximum increase of moss crust was3.52g·kg-1and the lowest increase of algae crust 1.82g·kg-1.In total nitrogen content,the maximum increase of moss crust was 0.75g·kg-1,and the minimum increase of algae crust was 0.45g·kg-1.The maximum increase of moss crust was 21.53g·kg-1,and the minimum increase of algae crust was 17.98g·kg-1.In total phosphorus content,the maximum increase of moss crust was 0.32g·kg-1,and the minimum increase of algae crust was 0.16g·kg-1.The maximum increase of moss crust was 2.31mg·kg-1 and the minimum increase of algae crust was 1.78mg·kg-1 in available phosphorus content.In the content of available potassium,the maximum increase of moss crust was18.58mg·kg-1,while the minimum increase of algae crust was 16.35 mg·kg-1.(3)It is proved that reasonable use of additives can effectively affect the growth of vegetation by using exogenous additives to artificially cultured biological crusts and the model of Hogland nutrient solution-plant growth regulator-water retaining agent was the best combination method.The combination mode of Hoagland nutrient solution,plant growth regulator and water retaining agent could effectively improve the vegetation coverage,plant height,plant density and other growth indicators.In this model,the coverage of moss crust reached 90%,the plant height reached 8.2mm,and the plant density reached more than 135 plants/cm2 during 60 days of rapid cultivation.The combination of Hoagland nutrient solution-plant growth regulator-water retaining agent mode can effectively construct a biological crust cultivation method suitable for karst rocky desertification area and form the corresponding artificial cultivation theory and technology system,and promote the comprehensive control measures for rocky desertification.(4)According to research and investigation,it is known that native species,lithophytic species and other biological crusts are widely distributed in the two demonstration areas,and mosses and mixed crusts are the main ones.By exploring the effect of biological crust on the improvement of soil physical and chemical properties in karst rocky desertification,the significance of biological crust on the improvement of soil physical and chemical properties was revealed.It has been proved that biological crusts have good effect on soil restoration in karst areas.By using artificial cultivation technology to build a technical system of biological crusts,forest-shrub and grass integration,and a new vegetation restoration model can be formed.Based on the conditions of different rocky desertification habitats,biological crusts are used to improve and repair the soil environment.It can help to restore vegetation in rocky desertification areas,construct ecological stability of plant communities,improve physical-chemical nature of the soil,increase soil organic matter content,enhance land bearing capacity and anti-erosion ability,promote the formation of soil aggregat and provide good prerequisites for the growth of vegetation.In the harsh habitat of rocky desertification area,biological crusts have become the new plant of environmental governance by virtue of its strong resistance to adversity and good ecological restoration function.In the future,we can combine the interaction mechanism between biological crust and karst process,stress tolerance characteristics of biological crust and biodiversity stability mechanism to realize the diversified development of comprehensive management means of rocky desertification. |
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