Carbon Sequestrated By Autotrophic Microorganisms And Its Content & Distribution In The Physical And Chemical Components Of The Representativesoil For Subtropical Area

Autotrophic microbe is widespread in the soil and has the function of photosynthetic carbon sequestration (assimilation of atmospheric CO2). However, the distribution of autotrophic microbe-assimilated carbon in soil organic and physical-chemical components was still unknown in the different ways of soil utilization. Therefore, the study used the continuous carbon isotope (14C-CO2) labeling combined with the simulation training test in laboratory, and soil organic matter, physical and chemical grouping methods. We studied the carbon sequestration function of autotrophic microbe in three different paddy and upland soil, and the content and distribution characteristics of autotrophic microbe in the physical and chemical composition of the tested soil. The results showed that:1. In the paddy and upland soil, the content of autotrophic microbe-assimilated carbon was 6.21-67.85 mg·kg-1, the contribution to soil organic carbon (14C-SOC/SOC) was 6.21?67.85%. In the active organic carbon pool of soil, the content of autotrophic microbe-assimilated carbon in soil microbial biomass carbon(14C-MBC) was 5.10?17.87 mg·kg-1, which was more than the content(0.71?4.02 mg·kg-1 in the soil soluble organic carbon(14C-DOC).The contribution of autotrophic microbe-assimilated carbon to soil microbial biomass carbon (14C-MBC/MBC) was 1.14?10.07%, the contribution to the soluble organic carbon (14C-DOC/DOC) was 0.93?8.94%. The contribution of the MBC was greater than the contribution of DOC. Meanwhile, the content of autotrophic microbe assimilation (14C-SOC) and soil microbial biomass carbon (14C-MBC) in paddy soil carbon was greater than the upland soil, but the soil soluble organic carbon (14C-DOC) content in upland soil was greater than the one in paddy soil.2. Autotrophic microbe-assimilated carbon, were mainly distributed in heavy fraction in large particle (0.02-0.2 mm and 0.2-2.0 mm), and less in soil small aggregation (0.002-0.02 and less than 0.002 mm) and light fraction, which suggested carbon sink. Meanwhile, the assimilated carbon contributed more to soil large aggregation and soil light fraction than that to in soil small aggregation and soil light fraction, and more content in paddy field than in dry land.3. In paddy and upland soil, autotrophic microbe-assimilated carbon were to varying degrees into the soil humus of humin (HM), humic acid (HA) and fulvic acid (FA) component. The autotrophic microbe-assimilated carbon content in Humin, humic acid and fulvic acid were 2.21?49.52 mg·kg-1,2.71?12.75 mg·kg-1 and 1.74?17.37 mg·kg-1. At the same time, the contribution of 14C-SOC in humin components to total 14C-SOC content in the soil and the content of SOC in humin was respectively 33.05?77.48% and 0.07?0.57%, which was larger than other components. In addition, autotrophic microbe-assimilated carbon content in the humus components of paddy soil was greater than that in the humus components of upland soil.