The Study On Dynamic Changes Of Soil Respiration In Three Patterns Of Carbon Sequestration Forest

The purpose of the carbon sequestration afforestation is to increase carbon sink,and soil respiration is one of the main ways of soil carbon loss.Therefore,studying the soil respiration of carbon sink forests with different afforestation patterns can more accurately assess the carbon sink function of carbon sink forest.This study selected three afforestation patterns of carbon sequestration forests in Wuhua County,Guangdong Province:artificial afforestation,interplanting,closing the land for reforestation.The soil respiration,soil temperature and moisture at 10 cm were measured by Automatic Soil CO₂ Flux System(LI-8100A)from December 2016 to July 2018.And we analyzed the soil bulk density and soil organic carbon content,and biomass factors in the aboveground and underground layers of vegetation.By studying the response of three afforestation patterns of carbon sink forests to soil respiration,and comparing soil respiration and its determinants of different afforestation models.The purpose is to understand the carbon sequestration capacity of forests in addition to the soil carbon sequestration,that is,carbon loss,so as to more accurately understand the carbon sink function(carbon fixation-carbon loss),and screen out the best afforestation capacity pattern.In addition,the reasons for the difference between carbon sink function and carbon loss are analyzed from environmental factors.The results show:(1)During the observation period,the soil respiration of artificial afforestation,interplanting and closing the land for reforestation was significant difference,and the average soil respiration was in turn:2.00±0.19,2.36±0.22 and 1.29±0.16?mol·m^-2·s^-1.There was no significant difference in average soil respiration between the interplanting and artificial afforestation patterns(P>0.05),but both of them in soil respiration was significantly greater than that of closing the land for reforestation.(2)There were significant seasonal differences in soil respiration rates among three afforestation patterns of carbon sequestration forests(P<0.01).Soil respiration in summer was significantly higher than in winter.Seasonal changes in soil respiration under different afforestation patterns were similar to changes in soil temperature at 10 cm.Soil temperature and humidity between the three afforestation patterns showed no significant difference(P>0.05).Furthermore,soil respiration and soil temperature were significantly related to the index among three afforestation patterns(P<0.01;R²=0.627,R²=0.643,R²=0.751).However,there was no significant linear correlation between soil respiration and soil water content among the three afforestation patterns,and their linear model fit was less than 30%.Besides,we did not find a significant difference in soil respiration temperature sensitivity among three afforestation patterns(P>0.05).(3)Vegetation factors showed extremely significant or significant differences in the three afforestation models(P<0.01 or P<0.05),but there was no significant difference in soil factors(soil bulk density and soil organic carbon content)(P>0.05).In addition,soil respiration and vegetation and soil characteristics of the three afforestation models were not significantly correlated(P>0.05).In the interplanting pattern of carbon sink forest,total biomass of existing vegetation(966.50±159.14 t·hm^-2),litter biomass(2.89±0.23 t·hm^-2),fine root biomass(2.82±0.30 g·m^-2)and soil organic carbon content(7.55±2.94 g C·kg^-1)were highest.The litter biomass in the artificial afforestation pattern was the lowest(1.32±41.13 t·hm^-2),but the soil bulk density was the largest(1.37±0.04 g·cm^-3).In the afforestation pattern of closing the land for reforestation,the total biomass(36.40±15.00t·hm^-2)of existing vegetation,fine root biomass(0.95±0.19 g·m^-2)and soil organic carbon content(3.82±0.33 g C·kg^-1)were lowest.In summary,there were significant differences in soil respiration among three afforestation patterns in carbon sequestration forests,due to the differences in vegetation structure and root biomass under different afforestation patterns.At the same time,seasonal differences in soil respiration were significant difference in each afforestation pattern.In addition,other soil properties(soil bulk density and soil organic carbon)had no significant effect on soil respiration.Although soil respiration in the interplanting pattern was the least sensitive to temperature,no significant differences have been found with the other two patterns.In the future work,more attention should be paid to the response of different afforestation patterns to soil microbial respiration,which is helpful to explore the response of soil microbial decomposition organic carbon to temperature and soil organic carbon stability among different afforestation patterns.It is contributed to finding the best afforestation pattern in the construction of carbon sequestration forests.