Experimental Study On Carbon Isotope Characteristics Of Different Plant Landscape Zones In Semi-arid Dune And Meadow

In order to study the characteristics of stable carbon isotope composition of the atmosphere,vegetation leaves and soil systems in the canopy of the semi-arid Sand Dune and meadow in different landscape zones and their responses to various influencing factors,in this paper,the stable carbon isotope technique was used to analyze five typical vegetation types,including semi-mobile Dune,Artemisia Halodendron,meadow corn and Reed,semi-mobile semi-fixed Dune and Caragana Microphylla Salix Gordejevii,comparing the changes of carbon content and?¹³C value of each vegetation during the growing season,the effects of persistent drought and continuous rainfall on them,and using weather stations and other measured meteorological and soil environmental factors,the variation characteristics of stable carbon isotope of different vegetation and its response to influence factors were studied.The main results are as follows:(1)The range of ?¹³C value of Artemisia halodendron leaves in growing season is-29.62‰?-27.56‰,the range of?¹³C value of Caragana microphylla leaves is-27.33‰?-25.81‰,and the range of?¹³C value of willow leaves is-28.83‰?-25.57‰The range of?¹³C value of meadow maize leaves was-13.40‰?-12.29‰,and that of reed leaves was-27.94‰?-26.68‰,which indicated that maize was a C₄ plant.The carbon content and?¹³C value of leaves in different ages of vegetation were different.Compared with the old leaves and litter,the new leaves had stronger carbon fixation ability and higher water use efficiency.The carbon content of reed leaves was sensitive to the monthly average rainfall,and the?¹³C value of five vegetation leaves was sensitive to the monthly average temperature and the monthly average rainfall.(2)The content of soil organic carbon in maize,Reed,Caragana Microphylla and Salix Gordejevii decreased with the increase of soil depth.The content of soil organic carbon was lower in late growth stage than in early growth stage and lower in middle growth stage than in meadow vegetation.The?¹³C values of 5 vegetation soils were all enriched with the increase of soil depth.The?¹³C values of corn,Reed,Caragana Microphylla and Salix Gordejevii soil were negative with the increase of soil water content,and the soil organic carbon content of meadow vegetation was greatly affected by soil water content,temperature and p H.(3)The soil turnover rate in Dune was higher than that in meadow,and the soil turnover rate in Salix Gordejevii was the fastest,followed by Artemisia Halodendron,and the soil turnover rate in meadow reed was the fastest and that in corn was the slowest.(4)The difference of ?¹³C value in the leaves of the shrubs changed greatly after the continuous drought,that is,the shrubs could adjust the water use efficiency of the leaves in time to cope with the drought,and the ability of coping with the drought stress was stronger.The difference of?¹³C value of Dune vegetation soil was found in all sampling layers,and the difference of?¹³C value of meadow corn was found in middle and deep layer soil,and that of reed soil was found in surface layer soil.Before and after continuous rainfall,the concentration of atmospheric CO₂ and the value of?¹³C in the canopy of Dune vegetation were significantly affected.Before and after rain,the?¹³C values of Artemisia Halodendron,Artemisia Halodendron,Caragana Microphylla Salix Gordejevii and phragmites Communis were different,which indicated that the above vegetation was more sensitive to rainfall.The?¹³C values of soil in all layers of dune vegetation were significantly different,the?¹³C values of meadow corn soil were between the surface layer and the middle layer,the?¹³C values of reed soil were between the middle layer and the middle layer.