Changsha Research Station for Agricultural and Environmental Monitoring and Key Laboratory of Agro-ecological Processes in Subtropical Region, Institute of Subtropical Agriculture, Chinese Academy of Sciences, Changsha, Hunan, 410125, China.
Appl Microbiol Biotechnol. 2014 Mar;98(5):2309-19. doi: 10.1007/s00253-013-5179-0. Epub 2013 Aug 30.
Soils were incubated continuously in an atmosphere of (14)CO2 and the distribution of labeled C into soil organic carbon ((14)C-SOC) was determined at 0-1, 1-5, and 5-17 cm down the profile. Significant amounts of (14)C-SOC were measured in paddy soils with a mean of 1,180.6 ± 105.2 mg kg(-1) at 0-1 cm and 135.3 ± 47.1 mg kg(-1) at 1-5 cm. This accounted for 5.9 ± 0.7% and 0.7 ± 0.2%, respectively, of the total soil organic carbon at these depths. In the upland soils, the mean (14)C-SOC concentrations were 43 times (0-1 cm) and 11 times (1-5 cm) lower, respectively, than those in the paddy soils. The amounts of (14)C incorporated into the microbial biomass (MBC) were also much lower in upland soils (5.0 ± 3.6% and 2.9 ± 1.9% at 0-1 and 1-5 cm, respectively) than in paddy soils (34.1 ± 12.4% and 10.2 ± 2.1% at 0-1 and 1-5 cm, respectively). Similarly, the amount of (14)C incorporated into the dissolved organic carbon (DOC) was considerably higher in paddy soils (26.1 ± 6.9% and 6.9 ± 1.3% at 0-1 and 1-5 cm, respectively) than in upland soils (6.0 ± 2.7% and 4.3 ± 2.2%, respectively). The observation that the majority of the fixed (14)C-SOC, RubisCO activity and cbbL gene abundance were concentrated at 0-1 cm depth and the fact that light is restricted to the top few millimeters of the soil profiles highlighted the importance of phototrophs in CO2 fixation in surface soils. Phylogenetic analysis of the cbbL genes showed that the potential for CO2 fixation was evident throughout the profile and distributed between both photoautotrophic and chemoautotrophic bacteria such as Rhodopseudomonas palustris, Bradyrhizobium japonicum, Rubrivivax gelatinosus and Ralstonia eutropha.
土壤在（14）CO2 的持续氛围中进行孵育，标记的 C 在剖面 0-1、1-5 和 5-17 cm 处的土壤有机碳（（14）C-SOC）中的分布情况。在稻田土壤中测量到大量的（14）C-SOC，在 0-1 cm 处的平均值为 1,180.6±105.2 mg kg（-1），在 1-5 cm 处的平均值为 135.3±47.1 mg kg（-1）。这分别占这些深度处总土壤有机碳的 5.9±0.7%和 0.7±0.2%。在旱地土壤中，（14）C-SOC 的平均浓度分别比稻田土壤低 43 倍（0-1 cm）和 11 倍（1-5 cm）。旱地土壤中微生物生物量碳（MBC）中（14）C 的含量也低得多（0-1 和 1-5 cm 处分别为 5.0±3.6%和 2.9±1.9%），而稻田土壤中（14）C 的含量（14）C 分别为 34.1±12.4%和 10.2±2.1%。同样，（14）C 溶解有机碳（DOC）中的含量在稻田土壤中（14）C 的含量也高得多（0-1 和 1-5 cm 处分别为 26.1±6.9%和 6.9±1.3%），而旱地土壤中（14）C 的含量（14）C 分别为 6.0±2.7%和 4.3±2.2%。固定（14）C-SOC、RubisCO 活性和 cbbL 基因丰度的大部分集中在 0-1 cm 深度，以及光仅限于土壤剖面的前几毫米，这突出了光养生物在表层土壤 CO2 固定中的重要性。cbbL 基因的系统发育分析表明，CO2 固定的潜力在整个剖面中都很明显，分布在光自养细菌和化能自养细菌之间，如沼泽红假单胞菌、日本根瘤菌、胶质红杆菌和恶臭假单胞菌。
