Zhang Xiao-Fang, Zheng Sheng-Meng, Xia Yin-Hang, Hu Ya-Jun, Su Yi-Rong, Chen Xiang-Bi
Key Laboratory of Agro-ecological Processes in Subtropical Region, Institute of Subtropical Agriculture, Chinese Academy of Sciences, Changsha 410125, China.
University of Chinese Academy of Sciences, Beijing 100049, China.
Huan Jing Ke Xue. 2020 Mar 8;41(3):1466-1473. doi: 10.13227/j.hjkx.201908218.
Land use type exerts important influences on soil organic carbon (SOC) and its fractions, and determines the stability of the carbon pool. Taking woodland as a reference, the content of SOC and its labile fractions[dissolved organic carbon (DOC), microbial biomass carbon (MBC), and particulate organic carbon (POC)] and non-labile fractions[mineral-associated organic carbon (MAOC)] in upland and paddy surface soils in hilly red soil regions were determined to explore the responses of SOC fractions to land use type. The results showed that the contents of SOC, MBC, POC, and MAOC ranked highest in paddy compared with upland and woodland. DOC content in woodland was significantly higher than in upland and paddy (<0.001). The proportion of each SOC fraction, i.e. DOC/SOC, MBC/SOC, POC/SOC, and MAOC/SOC, was in the range of 0.22%-0.93%, 1.62%-2.70%, 31.08%-40.00%, and 43.22%-56.82%, respectively. The contents of labile fractions (MBC and POC) and their proportions (MBC/SOC and POC/SOC) were in the order of paddy > woodland > upland. MAOC content ranked the highest in paddy but the lowest in upland, while MAOC/SOC exhibited the opposite trend. The correlation suggested that the labile fractions (MBC and POC) and inert fraction (MAOC) were significantly positively correlated with SOC (<0.001) in the three land use types, while no significant correlations were found between DOC and SOC and its fractions (>0.05). There was a significant positive correlation between POC and MBC in upland and woodland (<0.001). POC was significantly positively correlated with MAOC in the three land use types (<0.001). MAOC and MBC in paddy and upland were significantly positively correlated (<0.001). Therefore, compared with upland and woodland, SOC in paddy had a higher proportion of labile SOC fraction, but a lower proportion of inert fraction. Moreover, MBC content in paddy was not related to the accumulation of the labile fraction of POC, but positively related to the accumulation of the inert fraction of MAOC. In summary, agricultural land uses have great influence on SOC and its fractions in hilly red soil regions. Though paddy is beneficial for SOC sequestration, the proportions of labile fractions in its SOC are relatively higher, and thus it is vulnerable to loss due to improper agricultural management.
土地利用类型对土壤有机碳（SOC）及其组分具有重要影响，并决定了碳库的稳定性。以林地为参照，测定了丘陵红壤区旱地和水田表层土壤中SOC及其活性组分[溶解有机碳（DOC）、微生物量碳（MBC）和颗粒有机碳（POC）]以及非活性组分[矿物结合有机碳（MAOC）]的含量，以探究SOC组分对土地利用类型的响应。结果表明，与旱地和林地相比，水田中SOC、MBC、POC和MAOC的含量最高。林地中的DOC含量显著高于旱地和水田（<0.001）。各SOC组分的比例，即DOC/SOC、MBC/SOC、POC/SOC和MAOC/SOC，分别在0.22% - 0.93%、1.62% - 2.70%、31.08% - 40.00%和43.22% - 56.82%范围内。活性组分（MBC和POC）的含量及其比例（MBC/SOC和POC/SOC）顺序为水田>林地>旱地。MAOC含量在水田中最高，在旱地中最低，而MAOC/SOC则呈现相反趋势。相关性分析表明，在三种土地利用类型中，活性组分（MBC和POC）和惰性组分（MAOC）与SOC显著正相关（<0.001），而DOC与SOC及其组分之间未发现显著相关性（>0.05）。旱地和林地中POC与MBC显著正相关（<0.001）。在三种土地利用类型中，POC与MAOC显著正相关（<0.001）。水田和旱地中的MAOC与MBC显著正相关（<0.001）。因此，与旱地和林地相比，水田中SOC的活性组分比例较高，但惰性组分比例较低。此外，水田中MBC的含量与POC活性组分的积累无关，但与MAOC惰性组分的积累呈正相关。综上所述，农业土地利用对丘陵红壤区的SOC及其组分有很大影响。虽然水田有利于SOC固存，但其SOC中活性组分的比例相对较高，因此易因不当的农业管理而流失。
