Study On Soil Respiration Characteristics And Its Response To Hydrothermal Changes For Different Reconstructed Soil Mass

Global warming is one of the serious environmental problems related to human survival.Soil respiration is widely concerned by scholars because it participates in the global ecosystem carbon cycle and thus affects the global climate.At present,the research on soil respiration focuses on different ecosystems,different time and space angles,and initially forms the theory of soil respiration.In recent years,land remediation projects have evolved from traditional land leveling to soil mass rebuilding.Reconstruction soil mass has gradually become an important means to supplement cultivated land resources in the future,but research on soil respiration of rebuilding soil mass is still rare.In this study,four different reconstructed soil mass including meteorite,shale,sand and soft rock were added as research objects,and the field was reconstructed in the soil mass rebuilding experiment area of the waste rock beach in Shangwang Village,Tangyu Town,Mei County,and Baoji City,Shaanxi Province.Dynamic monitoring,from November 2017 to October 2018,the soil carbon flux measurement system?LI-8100?was applied to study the soil respiration changes,seasonal changes and soil respiration dynamic changes after rainfall in four reconstituted soils.The study was carried out and the hydrothermal factors of the four reconstructed soils were observed.The dynamic characteristics of soil respiration and its driving factors in reconstituted soil mass were studied.The main research progress and conclusions are as follows:?1?The diurnal variation of soil respiration for four reconstituted soil mass and their responses to soil temperature and soil volumetric water content were clarified.During the study period,the daily dynamics of soil respiration for four reconstituted soil mass showed a single-peak curve.The highest value generally appeared at 10:00,12:00 or 14:00 in Beijing time,and the lowest value appeared at 6:00 or 20:00.The maximum and minimum values of soil respiration for reconstituted soil mass occur respectively in August 2018 and December2017.The order of the daily variation soil respiration for the reconstructed soil in the observation month is Sand>Shale>Sandstone>Vermiculite.The pattern of heterotrophic respiration and autotrophic respiration in the respiratory component is basically similar for our reconstituted soil mass,the peak time is between 10:00 or 12:00,the valley value is at6:00 or 20:00,and is on the soil.The response model of soil respiration to soil temperature and volumetric water content was constructed.The response of soil respiration to soil temperature showed a significant exponential relationship,while the volumetric water content showed a quadratic curve relationship,and the two factors of soil temperature and volumetric water content were in a power-exponential model relationship.Both soil temperature and volumetric water content can explain the diurnal variation of soil respiration,but the interpretation ability was different.The interpretation ability of two-factor model was generally higher than 50.0%.The interpretation ability of temperature in single factor model was significantly higher than that of volumetric water content.It was not strong explanatory power,typically less than 50.0%.?2?The seasonal variation characteristics of soil respiration for four reconstituted soil mass and their responses to soil temperature and soil volumetric water content were investigated.During the observation period,the monthly mean soil temperature changes for the four reconstituted soil mass were basically consistent with the months when the soil respiration maximum and minimum values appeared.The soil volumetric water content was greatly affected by the precipitation.The reconstituted soil mass monthly mean soil total and its components respiration was the highest in summer and the lowest in winter,the maximum and minimum values with soil respiration were observed respectively in August and January2018.Differences in respiratory rates between soil heterotrophic and autotrophic respiration was Significant for the four reconstituted soil mass during the observation month?p<0.05?.Heterotrophic respiration had the highest monthly contribution rate to total respiration in January,and the autotrophic respiration was the smallest for the four reconstructed soil mass.In June,heterotrophic respiration of the reconstructed soil mass adding meteorites,shale and soft rock had the highest monthly contribution rate to total respiration,and autotrophic respiration was the smallest.In July,heterotrophic respiration of the reconstructed soil mass adding sand had the highest monthly contribution rate to total respiration,and autotrophic respiration is the smallest.The relationship function between Relationship function between soil respiration and hydrothermal influence factors showed that the two-factor model?power-exponential model?can better characterize the relationship between them.The single-factor model had much better interpretation of soil temperature?exponential model?than water?quadratic curve model?,seasonal variation and annual variation between soil respiration of the reconstructed soil mass and soil heat and power factor can be used exponential function and power-exponential function.?3?The dynamic changes of soil respiration and its components and hydrothermal influence factors for reconstituted soil mass during rainfall are revealed.The two rainfalls significantly reduced the soil temperature and improved the soil water condition.the first rainfall significantly stimulated the soil respiration rate of different reconstituted soil mass,but inhibited the soil heterotrophic respiration rate and stimulated the soil autotrophic respiration rate.The second rainfall generally inhibited the soil respiration rate of different reconstituted soil mass,but the inhibition rate of soil heterotrophic respiration rate was stronger than that of autotrophic respiration rate.For four reconstituted soils in different periods of two rainfalls,index model with the soil respiration rate and soil temperature,quadratic modelthe with the soil respiration rate and soil water content and the power-exponential model with the soil respiration rate and soil temperature and moisture can be used as the main factors that can determine the soil respiration of reconstructed soil mass.The change of soil volume water content before rainfall can determine the main influence factors of soil respiration rate changes.soil volume water content change obviously,water is the main influencing factor,soil volume water content are relatively stable,soil temperature is the main influencing factor,soil respiration are affected by soil temperature and moisture during rainfall.After the end of rainfall,water is the main influencing factor of soil respiration rate for reconstituted soil mass.?4?The temperature sensitivity variation characteristics of soil respiration and its components of four reconstituted soil mass at different time scales were summarized.The reconstituted soil mass with the addition of sand has the highest sensitivity,and the reconstituted soil with the addition of meteoritee has the lowest temperature sensitivity at the daily variation scale.Under the seasonal variation scale,the Q₁₀ of soil respiration,autotrophic respiration,and heterotrophic respiration for four reconstituted soil mass in winter and summer are all sand>shale>soft rock>meteoritee.The Q₁₀ of total soil respiration,autotrophic respiration and heterotrophic respiration are inconsistent in spring and autumn,but Q₁₀ was not significant in spring and autumn?p<0.01?.the temperature sensitivity of soil respiration and its components for four reconstituted soil mass decreased with increasing temperature,the lowest in summer and the highest in winter,whether it was daily or seasonal variation scale,the temperature sensitivity of autotrophic respiration temperature is greater than that heterotrophic respiration and total soil respiration for reconstituted soil mass,that is,the temperature sensitivity of autotrophic respiration is higher than that of heterotrophic respiration and total soil respiration.In summary,this paper mainly studies the changes of soil respiration dynamic changes and hydrothermal influence factors for four reconstituted soil mass under different time scales and extreme weather rainfall,the phase changes and adaptation laws of soil respiration and its components and hydrothermal influence factors for four reconstituted soil mass are clarified.The law of response of soil respiration to rainfall in reconstructed soil is revealed.The soil respiration and temperature sensitivity characteristics of four reconstituted soil mass were summarized at different time scales.Studying the characteristics of soil respiration dynamic changes for reconstructed soil mass will provide a scientific basis for accurate assessment of CO₂ emissions and the development of reasonable CO₂ emission reduction measures.It will also further understand soil respiration processes and mechanisms and promote the further development of carbon cycle theory.