Farmland Carbon Pool Composition And Emissions Characteristics Of Various Land Use Types In Fuzhou

Farmland carbon pools play an important role in global carbon pools.The fractions,turnover and stability of soil organic carbon and plant carbon sequestration are the main research contents of farmland carbon cycle.At the same time,farmland also releases carbon into the atmosphere in the form of CO₂ and CH₄.The study of the farmland carbon pools fractions and carbon emissions have important theoretical and practical significance for regional agricultural sustainable production and scientific management.Based on this,this paper selected paddy fields,vegetable fields and jasmine gardens as experimental plots to explore the carbon pools fractions and carbon emissions characteristics under different land use types in Fuzhou.The main results were showed as follows:（1）The total plant carbon sequestration of rice was significantly higher than that of vegetable and jasmine during the sampling period,which showed that rice>jasmine>vegetable（P<0.05）.Rice mainly relied on its grain and stem organs to sequestrate carbon,while vegetable and jasmine were mainly relying on leaf and stem organs to sequestrate carbon.Nitrogen（N）content in all organs of vegetable were significantly higher than those of rice and Jasmine（P<0.05）.The phosphorus（P）content of each plant was less affected by the growth period,and the P content of each organ was lower.The growth traits of each plant were quite different,vegetable root length was the shortest,moreover,leaf area was the largest and chlorophyll was the lowest（P<0.05）.（2）Soil organic carbon fraction was changed with time and its interaction with land use change.Soil organic carbon（SOC）,labile organic carbon（LOC）and microbial biomass carbon（MBC）in Jasmine fields were basically lower than those in paddy fields and vegetable fields.Soil dissolved organic carbon（DOC）was the lowest in paddy fields.In the 0-30 cm soil layer,the proportion of large aggregates with a size of>0.25 mm were vegetable fields>jasmine fields>paddy fields.Three stability parameters of MWD,GMD and DR0.25 were the lowest in the jasmine fields during sampling period,and the D value was higher in the jasmine fields.Soil carbon content was mainly concentrated in large aggregates（>0.25 mm）in vegetable fields.Ca-SOC content was generally low.Soil Fe（Al）-SOC content was higher in the 0-15 cm soil layer than that in the 15-30 cm soil layer.Soil residue-SOC content was significantly lower in jasmine fields than those of other soils.The number of fungi was relatively high in the paddy fields.There were fewer bacteria in July and the fungi/bacteria were low in the vegetable soil.（3）There was a significant difference in the peak period of CO₂ emissions from paddy fields,vegetable fields and jasmine fields.In April and August,the CO₂ emissions were the lowest from paddy fields compared to vegetable fields and jasmine fields,reaching their peaks in June and September.In June,August and September,the CO₂emissions reached the peaks in vegetable fields and jasmine fields.In May and August,the CH₄ emissions was the highest of paddy fields than those of vegetable fields and jasmine fields.The carbon emissions mainly came from CO₂ in each type of farmland.The comprehensive greenhouse effect was higher in vegetable fields and jasmine field than that of paddy fields.CO₂ was the most important greenhouse gas,and the contribution rate of greenhouse effect was more than 90%throughout the year.（4）The total carbon storage was highest in vegetable fields.The plant carbon pool was highest and the carbon emission was lowest in paddy fields.In addition,jasmine garden had the highest carbon emission and the lowest total carbon storage.