Wen Li, Li Dejun, Chen Hao, Wang Kelin
Key Laboratory of Agro-ecological Processes in Subtropical Region, Institute of Subtropical Agriculture, Chinese Academy of Sciences, Changsha, 410125, Hunan, China; Huanjiang Observation and Research Station for Karst Ecosystems, Institute of Subtropical Agriculture, Chinese Academy of Sciences, Huangjiang, 547100, Guangxi, China; University of Chinese Academy of Sciences, Beijing, 100049, China.
Key Laboratory of Agro-ecological Processes in Subtropical Region, Institute of Subtropical Agriculture, Chinese Academy of Sciences, Changsha, 410125, Hunan, China; Huanjiang Observation and Research Station for Karst Ecosystems, Institute of Subtropical Agriculture, Chinese Academy of Sciences, Huangjiang, 547100, Guangxi, China.
J Environ Manage. 2017 Oct 1;201:199-206. doi: 10.1016/j.jenvman.2017.06.048. Epub 2017 Jun 27.
Agricultural abandonment has been proposed as an effective way to enhance soil organic carbon (SOC) sequestration. Nevertheless, SOC sequestration in the long term is largely determined by whether the stable SOC fractions will increase. Here the dynamics of SOC fractions during post-agricultural succession were investigated in a karst region, southwest China using a space-for-time substitution approach. Cropland, grassland, shrubland and secondary forest were selected from areas underlain by dolomite and limestone, respectively. Density fractionation was used to separate bulk SOC into free light fraction (FLFC) and heavy fraction (HFC). FLFC contents were similar over dolomite and limestone, but bulk SOC and HFC contents were greater over limestone than over dolomite. FLFC content in the forest was greater than in the other vegetation types, but bulk SOC and HFC contents increased from the cropland through to the forest for areas underlain by dolomite. The contents of bulk SOC and its fractions were similar among the four vegetation types over limestone. The proportion of FLFC in bulk SOC was higher over dolomite than over limestone, but the case was inverse for the proportion of HFC, indicating SOC over limestone was more stable. However, the proportions of both FLFC and HFC were similar among the four vegetation types, implying that SOC stability was not changed by cropland conversion. Exchangeable calcium explained most of the variance of HFC content. Our study suggests that lithology not only affects SOC content and its stability, but modulates the dynamics of SOC fractions during post-agricultural succession.
农业弃耕被认为是增强土壤有机碳（SOC）固存的有效途径。然而，长期的SOC固存很大程度上取决于稳定的SOC组分是否会增加。在此，利用空间换时间替代法，对中国西南部喀斯特地区农业弃耕演替过程中SOC组分的动态变化进行了研究。分别从白云岩和石灰岩分布区选取了农田、草地、灌丛和次生林。采用密度分级法将土壤总有机碳分为游离轻组（FLFC）和重组（HFC）。白云岩和石灰岩上的FLFC含量相似，但石灰岩上的土壤总有机碳和HFC含量高于白云岩。森林中的FLFC含量高于其他植被类型，但白云岩分布区从农田到森林，土壤总有机碳和HFC含量均增加。石灰岩分布区四种植被类型的土壤总有机碳及其组分含量相似。白云岩上土壤总有机碳中FLFC的比例高于石灰岩，但HFC的比例则相反，这表明石灰岩上的SOC更稳定。然而，四种植被类型中FLFC和HFC的比例相似，这意味着农田转变并未改变SOC的稳定性。交换性钙解释了HFC含量的大部分变异。我们的研究表明，岩性不仅影响SOC含量及其稳定性，还调节农业弃耕演替过程中SOC组分的动态变化。
