不同土地利用方式对寿光市农业土壤有机碳分子结构和稳定性的影响

摘要

Converting agricultural soil to greenhouse significantly affects the characteristics of soil organic carbon due to the changes of cultivation measures. In order to investigate the effects of land use change on the molecular structures and stability of soil organic carbon (SOC), the molecular structures of SOC in farmland (FL), greenhouse soils that cultivated for 6 (6GH) and 12 years (12GH) and the abandoned greenhouse soil (AG) in Shouguang City were tested using the13C nuclear magnetic resonance (13C-NMR) technique. The results showed that: (1) land use change from FL to 6GH significantly increased SOC storage. Moreover, the SOC storage in 6GH (4.50 kg·m-2) was larger than that in 12GH (3.91 kg·m-2). However, AG (3.33 kg·m-2) had similar SOC storage with FL (3.07 kg·m-2). (2) The concentration of O-alkyl-C in SOC and ratios of hydrophobic carbon/hydrophilic carbon and aromatic carbon/alkyl-C in 6GH were larger than those in FL, respectively. However, these indices in 12GH and AG were similar to FL. (3) Compared with FL, 6GH, 12GH and AG had larger storage of labile (i.e. O-alkyl-C and carbonyl-C) and recalcitrant (i.e. alkyl-C and aromatic-C) SOC. The increased storage of labile SOC was larger than increased storage of recalcitrant SOC in 6GH, whereas the increased storage of recalcitrant SOC was larger than increased storage of labile SOC in 12GH and AG. These indicate that, compared with FL, most of the increased SOC in 6GH was labile fractions. However, the SOC stability is enhanced when the greenhouse is cultivated for 12 years or is abandoned. (4) The concentration of O-alkyl-C in SOC and ratios of hydrophobic-C /hydrophilic-C and aromatic-C/alkyl-C are sensitive indices to inflect the impact of land use change on SOC stability in the research region.%农田转变为设施菜地后,耕作措施的改变显著影响土壤有机碳的特征.为揭示不同土地利用方式变化对土壤有机碳分子结构及其稳定性的影响,以寿光市农业土壤为例,采用13C核磁共振技术分析农田转变化为不同种植年限设施菜地(种植6、12年)及设施菜地撂荒后土壤有机碳分子结构特征及其稳定性.结果表明,(1)农田转变化为设施菜地后土壤有机碳贮量显著增加,且种植6年设施菜地(4.50 kg·m-2)土壤有机碳贮量明显高于种植12年设施菜地(3.91 kg·m-2),设施菜地撂荒后(3.33 kg·m-2)土壤有机碳贮量降至农田水平(3.07 kg·m-2).(2)相对于农田,种植6年设施菜地土壤烷基碳相对含量、疏水碳/亲水碳比值及芳香碳/烷基碳比值明显低于农田,其他土地利用类型与农田无显著差异.(3)农田转变为设施菜地及设施菜地撂荒后,土壤易分解碳组分(烷氧碳+羰基碳)、难分解碳组分(烷基碳+芳香碳)贮量均有所增加,但种植6年设施菜地易分解碳组分贮量的增加量大于难分解碳组分的增加量,种植12年设施菜地及撂荒设施菜地则呈现相反的趋势.农田转变为设施菜地初期(种植6年)所增加的土壤有机碳主要为易分解组分,但随着种植年限延长及设施菜地撂荒,土壤有机碳稳定性逐渐增强.(4)烷氧碳相对含量、疏水碳/亲水碳比值及芳香碳/烷基碳比值可作为该区域土壤有机碳响应于土地利用方式转变的敏感性指标.