Study On Vegetation Distribution And Driving Factors Of Lake Beach Wetland In Ordos Platform

Inland wetland is an important carrier of surface water,an important indicator of regional climate and environmental changes,and also an important ecosystem participates in the regional water cycle,occupies an important position in arid and semi-arid climate zones.At the same time,as an important water conservation area in the oasis,it plays an important role in maintaining biodiversity,climate stability,and ecosystem balance.It is known as the "Island of Life" in the fragmented habitats interlaced with sand dunes and beams.The closed flow area of the Ordos platform is the second largest distribution area of saline-alkali lakes in China,with a large number of lakes and small area,which are very sensitive to environmental changes.Affected by climate warming and human activities in recent years,the lakes in the region have gradually shrunk,degraded and even disappeared,which has further led to the deterioration of the ecological environment.The phenomenon of "sand into the marsh and retreat" and the fragmentation and patching of salt marshes is outstanding,and the vegetation growing on it also shows corresponding changes.Studying the corresponding relationship between vegetation types and soil factors and climate factors of different lake and beach wetlands can explore whether the distribution of hidden vegetation is affected by climate factors like zonal vegetation,and what are the spatial driving forces.The distribution of which vegetation types indicate the process of soil desertification,wetland degradation and environmental evolution,and the corresponding distribution response interval of environmental factors of different habitat gradients.Through the analysis of environmental factors in the vegetation distribution area of lake beach wetland,the following results are obtained:1.The study area has investigated the vegetation types of four types of lake and beach wetlands,which are affected by the regional environment and local salinization,drought and other small environments.There are obvious differences in the distribution area,composition and species diversity of each vegetation type.Succulent salt-tolerant plant meadows are distributed in the southwestern part of the study area.Most of them are monophyletic communities formed by succulent plants such as the Kalidium cuspidatum community and the Suaeda glauca community,with higher differentiation,the lowest plant diversity,and the largest community importance value.Carex meadows are distributed in the central part of the study area,dominated by Carex duriuscula community,Carex duriuscula and other companion populations,the plant diversity is higher and the community importance value is higher.Gramineae grass and hybrid grass meadow are distributed in the northeastern part of the study area,dominated by gramineae grass and hybrid grass communities such as the Phragmites community and the Achnatherum splendens community,the degree of differentiation is low,the plant diversity is the highest,and the community importance value is the lowest.2.Vegetation in different areas of various types of lake and beach wetlands shows different spatial distributions and combinations with changes in soil moisture,salinity and particle size.In the typical lake and beach wetland of the succulent salt-tolerant plant meadows,with the increase of soil water and salt content and the refinement of the soil texture,the single superior community of succulent salt-tolerant plants transforms into a combination of succulent salt-tolerant plants and other dominant species.In the typical lake beach wetland of Carex meadows,with the decrease of soil moisture,the increase of salinity and the refinement of soil texture,the community of Carex duriuscula turns into Carex duriuscula+Phragmites australis,Carex duriuscula+Taraxacum sinicum,Carex duriuscula+Potentilla anserina and other plants combined community.In typical lake beach wetlands of gramineae grass and hybrid grass meadows,with the decrease of soil water and salt content and the coarsening of the soil texture,the community of Puccinellia distans+Carex duriuscula,and the community of Iris lactea change into the community of Phragmites australis+Carex duriuscula,Achnatherum splendens+Iris lactea community and so on.3.From the distribution characteristics of soil moisture,salinity and particle size of the typical lake beach wetlands of various meadow types,it can be seen that the soil moisture and particle size are the largest in the typical lake beach wetland of Carex meadow,gramineae grass and hybrid grass meadow typical lake beach wetland.Soil salinity is represented as fleshy salt-tolerant meadow typical lake beach wetlands are the largest.The response interval of soil water content of typical lake beach wetland of succulent salt-tolerant plant meadow is 10%?20%,the response interval of total salt is 5-30g/kg,and the response interval of particle size is 10?50?m.The response interval of soil water content of typical lake beach wetland of Carex meadow is 15%-30%,the response interval of total salt is 0?10g/kg,the response interval of particle size is 40?130?m.The response interval of water content of gramineae grass and hybrid grass meadow is 5%?30%,the response interval of total salt is 5?15g/kg,and the response interval of particle size is 50?130?m.It shows that the typical lake beach wetland of the succulent salt-tolerant plant meadow in the southwest of the study area close to Ningxia is not strongly affected by desertification,and the typical lake beach wetland type distribution area of Carex meadow has a greater hidden danger of desertification,and gramineae grass and hybrid grass meadow also show performance transformation into zonal desert grassland.Gramineae grass and hybrid grass meadows have the highest plant diversity in typical lake beach wetlands,followed by Carex meadows typical lake beach wetlands,the succulent salt-tolerant plants meadows are the smallest in typical lake and beach wetlands.4.The vegetation distribution in the lake beach wetland of the Ordos platform has obvious spatial heterogeneity.The NDVI value is generally low,mostly in the range of 0.2?0.3,and a small part of it in the range of 0.3?0.4.The vegetation type distributed in the southwest part of the study area is the succulent salt-tolerant plant meadows,SO42-accounts for 70.53%of the total anion,the corresponding soil type is sulfate soil.The middle part is covered with Carex meadow,HCO3-and SO42-respectively It accounts for 39.15%and 35.37%of the total anions,and the corresponding soil type is soda sulphate soil.The northeast part is covered with gramineae grass and hybrid grass meadows,SO42-and Cl-account for 46.42%and 31.13%of the total anions,the corresponding soil type is sulfate chloride saline soil.Due to the differences in the combination of water and heat and the micro-topography at the small regional scale,the water,salt,particle size and distribution status of different regions also show certain differences.The distribution of soil salinity in the whole area is opposite to the trend of soil moisture and particle size.Climate,as the background factor for the distribution of vegetation types,mainly affects the distribution of NDVI in the region through precipitation and dryness.From the southwest to the northeast of the study area,there is a spatial distribution of different vegetation types,mainly soil moisture,salt content,and the result of a combination of factors such as type and particle size.5.The plant diversity of the succulent salt-tolerant plant meadow lake and beach wetlands is most significantly affected by the total soil salt and Cl-,soil CO32-,K+,Cl-,Na+,Ca2+,HCO3-,water content,Mg2+,particle size,SO42-,pH are the main factors affecting the distribution of plant species,explaining 98.67%of the variation.The soil particle size of the Carex meadow lake and beach wetlands is a significant factor affecting plant diversity,soil pH,CO32-,particle size,water content,Ca2+,Na+ are the most important factors affecting the distribution of plant species,explaining 69.10%of the variation.SO42-is the main factor affecting plant diversity in gramineae grass and hybrid grass meadow and lake beach wetlands,soil Cl-,water content,SO42-,Ca2+,particle size,pH and CO32-are the main factors affecting the distribution of plant species,explaining 84.47%of the variation.