| Based on the observation of the changes of organic carbon in five types of soil and the distribution and grouping of soil organic carbon in nine years of long-term planting of ramie in the hilly area of South China,the carbon fixation effect of long-term planting of ramie was clarified,and the input,distribution and transformation of organic matter,physical and chemical properties of soil,physical and chemical grouping and microbial carbon metabolism activity were explored from three aspects of farmland organic carbon input,distribution and transformation The effects of factors such as sex and enzyme activity on soil carbon sequestration were analyzed.The mechanism of soil carbon sequestration in this area was analyzed comprehensively,which provided a scientific basis for improving soil carbon sequestration capacity and land productivity in red soil area.The main conclusions are as follows:(1)(1)After planting ramie for a long time,the surface organic carbon of different types of soil increased significantly,the content of organic carbon increased by 35.00%-92.34%,the accumulation of organic carbon in 0-40 cm soil layer accounted for 52.73-62.32% of the0-100 mm soil layer reserve,and the distribution of organic carbon on the profile had obvious "surface accumulation" phenomenon.According to the increasing range of organic carbon content during 2010-2019,the order is: Alluvium soil > Plate shale red soil > Q4 Red soil >Limestone red soil > Purple soil.(2)The aboveground biomass of ramie in different soil types was significantly different,and the dry weight of ramie in different soil types was 7.27-11.32t/ha.There was no significant difference in the content ofall elements in ramie.The aboveground biomass was the main factor that caused the difference in organic carbon input.The order of the aboveground biomass was: Q4 red soil > Plate shale red soil >Alluvium soil > Purple soil >Limestone red soil.(3)The distribution characteristics of aggregates and their organic carbon content in different soil types and the carbon content in humus have the same law.With the increase of particle size,the content first increases and then decreases.The content of 0.053-0.25 mm is the highest,the average content reaches 43.13%,and the organic carbon content of aggregates is 10.11-24.91g/kg,which has the trend of increasing with the increase of particle size.Humic substances were the highest in humic group,accounting for 54.02-69.28% of the total organic carbon.(4)Different types of soil microbial activity and soil enzyme activity are significantly different,different types of carbon source utilization has a unified rule.According to the activity of microbial carbon metabolism,the order is: Alluvium soil> Limestone red soil > Purple soil > Q4 red soil > Plate shale red soil.The utilization of carbohydrates and amino acids by microorganisms is stronger,followed by carboxylic acids and polymers,while phenolic acids and amines are the weakest.Six types of carbon sources can be divided into acid carbon sources and non acid carbon sources.(5)The results of comprehensive analysis on key factors of carbon sequestration showed that soil fertility,organic matter input and soil texture were positively correlated with carbon sequestration index,soil texture,soil fertility index and organic matter input were positively correlated with carbon storage,which indicated that good soil structure could affect the supply of soil fertility,improve the yield of ramie,andincrease the input of organic matter The organic carbon content of farmland soil was increased,while the acid carbon source and non acid carbon source had positive and negative correlation with the distribution of carbon fixation index,which indicated that the soil microorganism could form more stable macromolecular humus substances to promote the fixation of organic carbon and facilitate the supply of fertilizer,it can promote the circulation of soil fertility,increase soil fertility,and then increase the biomass and organic matter input of the above ground. |
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