Study On Soil Physical And Chemical Properties,Salinity Thresholds And Microbial Responses Of Saline Meadows Wetlands In Desert Steppe

The saline meadow wetland is a small natural oasis in the desert steppe area.It is not only a carrier of species diversity,but also an important land reserve resource in the region.The continuous intervention in the system cannot be ignored.Ecological threshold refers to a series of qualitative change points and qualitative change trajectories corresponding to a biological/ecological system corresponding to the environment.The study on the threshold of soil salinity in the vegetation of halo-salt meadow wetlands can determine the survival status of the system to a certain extent and predict the future evolution.The niche of vegetation is different,and the soil threshold is obviously different.so the distribution of other soil components in different vegetation types is also worth exploring.In this study,through the investigation of different types of halophyte meadow vegetation in the inland closed(inland)flow area of Ordos,the understanding of soil physical and chemical properties,the exploration of soil salinity threshold and the response of soil microbial distribution,the following results were obtained:1.The structure and composition of plant communitiesA total of 48 plants were investigated,constituting 4 vegetation subtypes and 24 communities.Among different types of meadows,the succulent and salt-tolerant plants in the meadow community are relatively simple in plant composition,with a high degree of community differentiation,high importance,and low plant diversity;Carex meadow communities have higher plant cover and density,and community height Low:the height and diversity of community plants in grass meadows are relatively high;the degree of differentiation of hybrid grass meadow community plants is low and the diversity is high.2.Soil physical and chemical properties of different types of saline meadowsThe soil water retention capacity differs among different vegetation types.Carex meadows perform better,and succulent salt-tolerant plants meadows perform lower.The mechanical composition of the soil in the study area is mainly clay particles and fine sand particles,powder particles account for a small part,and coarse sand particles account for a small part;among them,the Carex meadow soil is relatively coarse,and there may be a stronger hidden danger of desertification;on the soil layer profile The surface layer of the 4 types of meadow soil is fine,showing that the vegetation has a strong interception effect on wind and sand.Among the four types of meadow soil nutrient accumulation,the accumulation effect of soil organic carbon,total nitrogen and alkali-decomposed nitrogen in Carex meadow and hybrid grass meadow is good;the accumulation of total phosphorus and available phosphorus in succulent salt-tolerant plant meadow Higher,the cumulative effect of available potassium is not good,and the degree of mineralization is higher.3.Soil salinity thresholds of different types of halophytes and typical plantsThe salinity of salt marshes bare land is extremely high,which is not suitable for plant growth;the succulent salt-tolerant plant meadow soil has extremely high salt content,and the threshold values of soil total salt,pH,SO42-,Na+,Mg2-,Cl-and Ca2+ are within 10?20g/kg,7?8.5,20?30g/kg,6?10g/kg,4?10g/kg,2?4g/kg and 1?2g/kg;Carex meadow,grass meadow and weed meadow are relatively low in soil but relatively alkaline Stronger,soil total salt,SO42-,Mg2+,Cl-and Ca2+ are lower,pH is higher,the threshold is 8.5-9.5.Kalidium cuspidatum show strong adaptability in high-salt environments,with a total salt threshold of 10?20 g/kg;a soil pH threshold of 7?8.5,and more abundant ions in the soil are SO42-,Na+,Cl-,Mg2+ and Ca2+.Suaeda glauca has a strong adaptability to both saline soil and alkaline soil.in which the soil pH threshold ranges from 9.5 to 10.Carex duriuscula has a certain adaptability to alkaline soil,but is not suitable for growth on saline soil.The total soil salt and pH thresholds are 0?2 g/kg and 8.5?9.5,respectively.Phragmites australis is not suitable for survival in saline-alkali land.The distribution range of total soil salt and pH is relatively low,but it has a strong preference for K" and Ca2+ in the soil.Achnatherum splendens has relatively strong saline-alkali tolerance characteristics.The threshold of soil total salt is 4?8g/kg;the threshold of soil pH is 8.5?9.5.Puccinellia distans has a certain ability to resist saline-alkali,the total salt distribution in the soil is 0?5g/kg,the pH is 8.5?.5,the optimal habitat is not obvious.Agropyron crisratum can live in a certain degree of saline environment.The niche of the long-leaved Halerpestes ruhenica and Taraxacum mongolicum are similar in the soil saline-alkaline environment.They are adapted to live in a low-saline environment.The K+in the soil has a certain distribution,and the threshold is 0.2?0.3g/kg.Potentilla is not suitable for living on saline land.the soil is rich in Mg2+.4.Response characteristics of soil microorganisms in different types of halophytesIn terms of the number of microorganisms,Carex meadow,grass meadow and weed meadow are the most,followed by succulent and salt-tolerant plant meadow.and the bare salt marsh is lower.In terms of microbial composition,the research area mainly includes Proteus(class)of the phylum,and Ascomycete(class)of the phylum,and some special microorganisms also exist in the same area.There are many succulent salt-tolerant plant meadows,grass meadows and weed grass meadows with more soil fungi.In terms of diversity of microbial communities,Carex meadows and weedy meadows are higher,and bare salt marshes and succulent salt-tolerant plants are lower.5.The relationship chain of soil salinity in halophyte wetlandsAmong the functions of soil salinity indicators,Na+,Cl-,SO42-and Mg2+ can indicate the degree of development of saline soil,CO32-,HCO3-and K+ can indicate the development status of alkaline soil;NaCl,NaCl,The content of Na2SO4,MgCl2 and MgSO4 is relatively high,and it is suitable for the saline soil environment;Carex meadow,grass meadow and weed grass meadow soil have relatively high K2CO3and KHCO3 content,and they are suitable for the alkaline soil environment.The plant characteristic value has a certain degree of indication to the soil salinity.The dominant plant species in the community have a higher degree of differentiation and a higher soil alkalinity and a relatively stronger salt content.The alkaline soil has higher water content,nitrogen and organic carbon content;the relatively salty soil has a finer texture and higher phosphorus content.In terms of the relationship between soil microorganisms and soil salinity,the alkalinity of the soil has an effect on bacteria,and the K+ content in the soil has a certain effect on fungi.