Characteristics And Influencing Factors In Soil Respiration Of Different Reclamation In Coastal Saline Soil

The study selected the saline-alkali wasteland,cotton monocropping fields,and wheat and corn continuous cropping fields in the Yellow River Delta as the research object.The LGR carbon flux measurement system was used to determine the daily variation and seasonal variation of soil respiration rate.At the same time,soil and air temperature and humidity,soil physicochemical properties and soil microbial biomass carbon were measured to study and analyze the spatio-temporal dynamic changes of soil respiration and its impact factors under different modes of cultivation.Using spatial-temporal iterative methods,we selected the 0,10¹5,30³5,and 60⁷0 years wheat/maize continuous cropping soil as the research object,and explored the effects of different cultivation history on soil respiration and carbon storage.This study will provide basic data for constructing regional soil carbon model of saline-alkaline farmland,and also provide a reference for estimating and predicting the evolutionary trends and effects of soil organic carbon density in coastal saline areas in eastern China.The main findings are as follows:1.The effects of different reclamation methods on soil respiration were studied through different methods of reclamation tests.The effects of different hydroponic methods and soil physical and chemical factors on soil respiration were analyzed.?1?The soil respiration rate of different cultivation methods showed obvious diurnal variation and seasonal variation.The soil respiration was wheat/maize continuous cropping>cotton field>wasteland.The daily variation pattern of wheat/maize continuous cropping,cotton field monocropping,and uncultivated soil respiration were basically the same,all showed obvious unimodal curves.The soil respiration rate gradually increased from9:00 to 12:00,and the soil respiration rate reached the maximum at 12:00 noon.Values,the n soil respiration rate gradually decreased,reached a minimum around 24:00.Soil respiration showed obvious seasonal changes.The average soil respiration rate ranged from-0.12¹.58?mol·m^-2·s^-1 in different seasons,and the soil respira tion rate averaged over August>April>October>December,and the soil in December wasteland.Breathing is negative.?2?Soil respiration is affected by many factors,among which surface soil microbial biomass carbon and soil moisture are the dominant conditions affecting soil respiration.The variance explained by the two principal components accounts for 96.20%of the total variance.The soil respiration rate was significantly correlated with soil microbial biomass carbon,organic carbon,total nitrogen,pH,available phosphorus,and air humidity?p<0.01?,and was significantly correlated with available potassium and air temperature?p<0.05?,and bulk density,The soil temperature was significantly negatively correlated?p<0.01?and negatively correlated with the total salt content?p<0.05?.The diurnal changes in soil respiration of different cultivation methods were positively correlated with surface air temperature,soil surface temperature,soil moisture content,and soil respiration.The correlation?p<0.01?was significantly negatively correlated with surface air humidity and soil respiration?p<0.01?,and the composite function of soil temperature,humidity,and soil respiration was the determination coefficient R² of 0.612⁰.782.?3?The studies have shown that the soil organic carbon stocks in continuous cropping of wheat/maize?WM?and cotton fields?CF?have increased significantly?p<0.05?,and the soil carbon pools have increased by 44.93%and 40.32%respectively.It is said that within a certain time frame,the soil is cultivated and organically The carbon stocks show an increasing trend and have a certain carbon sink function.2.In order to further explore the effect of reclamation age on soil respiration and carbon storage,a typical model of continuous cropping o f wheat/maize?WM?was chosen to explore the changes of soil respiration and carbon processes in different reclamation years with the method of space-time replacement.?1?The longer the soil respiration rate for continuous cropping of wheat/maize?WM?,the greater the soil carbon emission increases with the increase of reclamation years.The change of soil respiration rate in different years of reclamation showed a clear change pattern.With the increase of reclamation years,the soil respiration rate showed a gradual increasing trend.The soil respiration rate was 60⁷0 a>30³5 a>10¹5 a.The soil respiration rates of 0a,10¹5 a,30³5 a,and 60⁷0 a increased by 1.77,3.35,and 4.48 times,respectively,compared with 0 a.?2?The soil organic carbon density in different years of reclamation?0 a,10¹5 a,30³5a,and 60⁷0 a?was a significant difference?p<0.05?.The organic carbon density increased with the increase of reclamation years.By analyzing the soil organic carbon density in different reclamation years,it was found that the 60,70,30,35,and 10-15 years of reclaiming utilization increased by 77.37%,38.89%,and 21.40%,respectively,increased by 22.43%compared with 0 a.