Study On The Characteristics Of Soil Respiration And Its Influencing Factors In Karst Region

Soil respiration is the most important way and type of carbon circulation between soil carbon pool and atmospheric carbon pool.It is an important expenditure item of terrestrial ecosystem carbon cycle and plays a decisive role in climate change.This paper takes 8 typical land use patterns(artificial grassland,natural grassland,dry land,bamboo forest land,shrub forest land,coniferous forest land,broad-leaved forest land and mixed coniferous and broad-leaved forest land)in the dolomite area of Shuanghedong National Geopark as the research object.Using the soil respiration measurement system(SRS-SD2000,ADC,UK),from August 2019 to March 2020,soil respiration and its main environmental factors were regularly measured,and the daily and seasonal dynamics of soil respiration of various types of land were analyzed.Characteristics and their relationship with environmental factors such as soil temperature and humidity,combined with single-factor models and correlation analysis methods,explore the main influencing factors of soil respiration and its response characteristics to the environment.The result shows:(1)Under the interference of no precipitation events,soil environmental factors have obvious diurnal and seasonal changes.The soil temperature of various vegetation types changes significantly day and night,all showing a single-peak change pattern,from 12:00 to 16:00 The maximum value appears,and the minimum value appears from 4:00 to6:00,which is consistent with the change trend of atmospheric temperature.The seasonal variation of soil temperature of each land type shows the trend of summer>autumn>spring>winter.Compared with the change of soil temperature,the change of soil moisture is not significant in both day and night changes or seasonal changes.In general,summer and autumn are higher than winter and winter.The characteristics of spring.(2)The soil respiration rate of each land use mode presents roughly the same diurnal variation trend,all presenting a single-peak change characteristic of "high day and low night".The maximum daily change appears between 13:00 and 15:00,and the lowest The value appears between 3:00 and 5:00,and the amplitude is large during the day and small at night.The daily average soil respiration values of different land use types are significantly different,and the overall performance is:bamboo forest land> artificial grassland> coniferous forest land>coniferous and broad-leaved mixed forest land> shrub forest land>broad-leaved forest land> natural grassland> dry land.The coefficient of variation between the same planting cover is smaller than the coefficient of variation between seasons,indicating that environmental factors have a greater impact on soil respiration compared with vegetation types.(3)The soil respiration rate of different land use patterns is generally characterized by summer>spring>autumn>winter,and also shows a unimodal seasonal change trend.From spring to summer,the soil respiration rate increases,reaching the highest value in summer,and then gradually weakening.It reaches the lowest value in winter,which is roughly the same as the seasonal variation trend of soil temperature in the study area.The bamboo forest land and artificial grassland with more developed root systems have greater seasonal variation,while the arbor forest has a gentler seasonal variation.(4)In the single-factor equation simulation of soil respiration changes in day and night,soil respiration is significantly positively correlated with soil temperature,and negatively correlated with soil moisture.In general,the fitting degree of soil temperature model at night is better than that in daytime,while soil temperature during daytime The degree of fit of the humidity model is better than that at night.In different seasons,the soil temperature fitting equation is better than the soil moisture equation.(5)The content of soil organic carbon is positively correlated with changes in soil respiration(P<0.01),which will promote soil respiration to a certain extent.The study found that the influence mechanism of topographic factors such as slope position and slope on soil respiration in this area is unclear,and further research is needed.It shows that temperature is the main influencing factor of soil respiration changes in this study area.