In order to explore the effects of long-term nitrogen (N) input on the content and chemical structure of different organic carbon fractions in meadow steppe soil, the meadow steppe in northeast Inner Mongolia was taken as the research object, six N input levels were setup in 2010, i.e., 0 (CK), 30, 50, 100, 150 and 200 kg(/hm2·a), the contents and infrared spectra of different soil organic carbon fractions were determined. The results showed that:1) Compared with CK, soil total organic carbon (SOC) was increased by 0.3%-13.6% under long-term nitrogen input, mainly due to the increase of particulate organic carbon (POC, 9.22%-16.39%), but light organic carbon (LOC) was decreased. 2) The results of principal component analysis (PCA) of infrared spectra showed that LOC mainly came from aliphatic carbon, aromatic carbon and phenolic alcohol compounds, POC came from aromatic carbon and phenolic alcohol compounds, and mineral-bound organic carbon (MOC) was from alkyl carbon and polysaccharides. 3) Compared with CK, the relative strengths of alkoxy carbon (monosaccharide + polysaccharide) in litter and LOC functional groups were decreased, the relative strengths of alkyl carbon and aromatic carbon were increased, the relative strengths of alkoxy carbon, alkyl carbon and aromatic carbon in POC and MOC functional groups were increased, and the relative strength of phenolic compounds was decreased under nitrogen treatment. The structural stability of organic carbon (aromatic carbon/aliphatic carbon) in litter and its different soil carbon fractions under nitrogen treatment was higher than that of CK. 4) SEM results showed that with the increase of nitrogen application, the formation of POC and MOC was promoted by increasing soil aboveground biomass (AGB), but the decrease of soil pH caused by nitrogen addition in turn promotes the decomposition of MOC. These results showed that the increase of SOC under long-term nitrogen input was mainly from the increase of soil POC. With the increase of nitrogen application, the input of plant carbon increased SOC and improved the chemical structure stability of different soil organic carbon fractions by promoting the accumulation of aromatic carbon such as lignin in litter residues. In summary, the results emphasized the importance of soil particulate organic carbon under nitrogen input and the accumulation of lignin derivatives in litter may be the key processes to mediate soil carbon sequestration under nitrogen input.
裴志福,红梅,武振丹,卢俊艳,张月鲜,沈钦国.草甸草原土壤不同组分有机碳含量及化学结构对长期氮输入的响应[J].土壤,2022,54(3):481-489. PEI Zhifu, HONG Mei, WU Zhendan, LU Junyan, ZHANG Yuexian, SHEN Qinguo. Responses of Soil Organic Carbon Content and Its Chemical Structure of Different Components to Long-term Nitrogen Input in Meadow Steppe[J]. Soils,2022,54(3):481-489复制