Response Of Karst Cyanobacterial Species Diversity To The Desertification Soil Environmental Succession

The national 14^thFive-Year Plan calls for the scientific promotion of comprehensive control of karst desertification,and the effect and process of control is one of the important bases for measuring the achievement of fragile ecological environment restoration and sustainable development in the region.Soil restoration is a important issue in the control of karst desertification,and cyanobacteria,as one of the important surface cover organisms,are important research objects to explore new pathways for ecological restoration of desertification soils.which are important for responding to the evolution of desertification ecological environment and expanding the ways of desertification soil control.Based on the theories of geography,ecology,environmental co-evolution,ecological and environmental restoration,scientific problems and scientific and technological needs such as the co-evolution of cyanobacterial species diversity and soil environment,response mechanisms and soil restoration strategies in karst desertification areas.In Guizhou plateau,which represents the general structure of karst ecosystem types in southern China,the Shibing Karst,Bijie Salaxi,and Guanling-Zhenfeng Huajiang were selected as the study areas.From 2020 to 2023,through the study area survey and sample collection,using experimental analysis,cluster analysis,one-way ANOVA,correlation analysis,principal component analysis,redundancy analysis,and comparative analysis,around the basic frontier research on the biodiversity of algal crust cyanobacteria in karst desertification control will focus on elucidating the composition and change patterns of cyanobacterial species,diversity characteristics under different levels of desertification soil environment,and reveal the synergistic evolution of cyanobacterial species,soil properties and evolution patterns,reveal the synergistic evolution characteristics and response mechanisms between the two,screen the dominant cyanobacteria to improve the soil,and propose remediation strategies for desertification soils,providing scientific references for the research of desertification cyanobacteria and soil treatment and improvement.（1）There were a total of 200 species of cyanobacteria distributed across 22genera,2 classes,5 orders,and 6 families were found in the three study areas with different degrees of karst desertification,and there was a obvious dominance phenomenon.Inorderofproportion,Oscillatoriales（39.00%）,Scytonematales（24.50%）,Chroococcales（23.00%）,Nostocales（11.50%）,Rivulariales（2.00%）,of which filamentous cyanobacteria were overwhelmingly dominant,accounting for 77%;The cyanobacteria in the three karst desertification study areas belong to the Nostocaceae,Oscillatoriaceae,Scytonemataceae,Rivulariaceae,Chroococcaceae,Cyanostylonaceae,Nostoc,Anabaena,Tolypothrix,Scytonema,Plectonema,Calothrix,Raphidiopsis,Oscillatoria,Lyngbya,Microcoleus,Schizothrix,Schizothrix,Symploca,Spirulina,Gloeocapsa,Aphanocapsa,Aphanathece,Gloeothece,Microcystis,Chroococcus,Asterocapsa,Cyanostylon.（2）Differences in cyanobacterial diversity and species composition were found in different desertification study areas.In the moderate-severe desertification area of Huajiang,the number of cyanobacteria species was the largest,94 species,belonging to 5 families and 12 genera,the dominant family was Oscillatoriaceae,and the dominant genera were Oscillatoria and Lyngbya.In the potential-mild desertification area of Salaxi,a total of 77 species of cyanobacteria were found,belonging to 5 families and 17 genera,the dominant family was Chroococcaceae,and the dominant genera were Gloeocapsa and Oscillatoria.In the no-potential desertification area of Shibing,a total of 80 species of cyanobacteria were found,belonging to 5 families and 14 genera,the dominant family is Scytonemataceae,and the dominant genera are Scytonema and Gloeocapsa.Margalef richness index and Shannon-Wiener diversity index and in the three desertification areas were in the same order.The Margalef index was Salaxi（3.69）>Shibing（2.97）>Huajiang（2.42）.Shannon-Wiener index is Salaxi（3.56）>Shibing（3.08）>Huajiang（3.01）,indicating that Salaxi has the most abundant and diverse species.In the four different community habitats,the richness and diversity index varied among the different study areas,with the highest diversity in shrubland and arbor woodland in general.Huajiang has the largest richness and diversity index of arbor woodland of 2.89 and 3.19,and the largest number of species in shrubland of 40 species.Salaxi has the largest richness and diversity index of shrubland of 3.82 and 3.54,and the largest number of species in shrubland of 37 species.Shibing has the largest richness index of shrubland of 2.82and the largest diversity index in bare land of 2.93,and the largest number of species in arbor woodland of 48 species.The biomass of algal crusts in different desertification study areas showed Salaxi>Shibing>Huajiang,which was consistent with the trends of cyanobacterial richness index and diversity index.（3）Soil properties were found to change with the succession of karst desertification level and the change of plant community,and the soil property factors affecting cyanobacterial species diversity and the response mechanisms between cyanobacterial species diversity and soil properties were elucidated.There was no obvious difference in p H between the three desertification study areas,which were all neutral to acidic,ranging from 5.73 to 6.85.Soil capacity is the largest in Shibing,and water content,field water holding capacity,and total porosity are the largest in Salaxi,followed by Shibing,and the lowest in Huajiang.Soil nutrients（organic carbon,total nitrogen,available nitrogen,total phosphorus,available phosphorus）increased with the deepening of the desertification degree,with Huajiang being the largest,followed by Salaxi,and the lowest being Shibing.Soil property factors affecting cyanobacterial species diversity were water content（0-5cm）,organic carbon,and total nitrogen,where water content（0-5cm）and total nitrogen were significantly and positively correlated with richness index and diversity index（p<0.05）,water content was the primary factor affecting cyanobacterial diversity,and species number was significantly and positively correlated with organic carbon（p<0.05）.There is a synergistic evolution of cyanobacterial species composition and diversity with the evolution of the soil environment.In the moderate-severe desertification area,the soil texture is mainly fine sand,rich in organic carbon and nitrogen,with cyanobacteria in the non-heterocystic Oscillatoriaceae as the dominant and common species.In the potential-mild desertification area,the soil coarse sand proportion is relatively large,the surface water content is large,organic carbon and total nitrogen are more abundant,and cyanobacteria of the globular Chroococcaceae are the dominant and common species.In the no-potential desertification area,the soil is mainly fine sand with moderate water content and relatively poor in nutrients,with cyanobacteria of the heterocystic Scytonemataceae as the dominant and common species.（4）Six dominant cyanobacteria in different desertification areas that can be applied to soil remediation were screened,and the effects of different dominant cyanobacteria on the particle composition,p H and soil nutrient enhancement of desertification soils were quantified.The results showed that the inoculation of cyanobacteria changed the soil particle,and all cyanobacteria,except Gloeocapsa montana,increased the content of soil silt and clay particles and decreased the content of soil sand particles to different degrees.The inoculation of all cyanobacteria increased soil p H and adjusted soil acidity.Overall,inoculation of cyanobacteria all improved soil nutrient content,but the restoration effects varied among cyanobacteria,Scytonema hofmanni showed the greatest increment of organic carbon and available nitrogen,Lyngbya attenuata showed the greatest increment of total nitrogen,and Nostoc commune showed the greatest increment of total phosphorus and available phosphorus,and proposed a remediation strategy for desertification soils to provide a reference for soil remediation.