Characteristics Of Soil CO₂ Flux Emission And Temperature Sensitivity In Larix Gmelinii Forests In Xingan

It is of great significance to study the temporal change characteristics of soil CO2 and its response to environmental factors of Larix gmelini forest,which is the main tree species in Daxinganling.In this study,LGR soil greenhouse gas long-term continuous observation system(dynamic chamber method)was used to monitor the diurnal and monthly changes of soil CO2 in Larix gmelinii forest from April to September 2019,as well as the response degree to water vapor concentration and soil temperature at different depths.The results provide a reference for the systematic study of carbon cycle and soil carbon emission in Daxing'an Mountains.(1)The soil CO2 emission rate of Larix gmelinii forest in Xing'an is as follows:August>July>September>June>May>April.The soil CO2 shows a single peak curve,and there is a short peak in April.There is obvious day night asymmetry in the rate of soil CO2 emission,which shows a single peak in the daytime,and reaches the maximum at noon or afternoon.At night,the emission rate is stable,and the minimum value appears in the early morning or the alternate period of day and night.(2)During the whole research period,the change of soil CO2 flux has a very significant correlation with soil temperature in different depths,among which the correlation degree with temperature is the smallest(R2=0.67,P<0.01),and the correlation degree with soil 10cm temperature is the largest(R2=0.83,P<0.01).(3)The sensitivity of soil CO2 emission rate to temperature is increasing with soil depth,which shows that Q10(surface temperature)<Q10(5cm temperature)<Q10(10cm temperature).During the whole study period from April to September,Q10 value of soil CO2 and surface temperature is 5.64,Q10 value of soil 5cm temperature is 6.30,Q10 value of soil 10cm temperature is 7.24.There are obvious differences in Q10 value in different months.In July,the growth rate of soil CO2 is the largest,Q10 value is the highest,the fluctuation of soil CO2 in June is small,Q10 value is the smallest.(4)Larix gmelinii forest is the source of soil CO2 emission.During the period of soil ablation(April to May),the amount of soil CO2 emission is 0.96t/hm2,accounting for 9.05%of the total.During the growth season(June to September),the amount of CO2 emission is 9.65t/hm2,accounting for 90.95%of the total.The CO2 emission during the whole study period was 10.61 t/hm2.