喀斯特地区植被恢复下土壤活性有机碳与碳库管理指数的演变特征

植被恢复通过改变碳输入和转化速率，影响陆地生态系统的碳循环.为探明喀斯特地区植被恢复过程中土壤活性有机碳组分与碳库管理指数的演变特征，以喀斯特地区草地序列（5、10、15和20 a）、灌木序列（5、10、15和20 a）和园地序列（5、10和15 a）土壤为研究对象，以相邻农田为对照（CK），分析了不同植被恢复年限对土壤有机碳（SOC）、易氧化有机碳（ROC₃₃₃、ROC₁₆₇和ROC₃₃，即能被333、167和33 mmol·L^-1 KMnO₄氧化的土壤活性有机碳）、微生物量碳（MBC）、溶解性有机碳（DOC）及碳库管理指数（CPMI）演变的影响.结果表明，与CK相比，0~40 cm土层草地、灌木和园地序列平均SOC含量分别增加了70.77%、114.40%和50.17%.在0~20 cm土层，随恢复年限增加，草地序列和园地序列的SOC含量呈先升后降势态，灌木序列呈先升后降再升势态，ROC₃₃₃、ROC₁₆₇和ROC₃₃与对应序列的SOC变化势态一致；在20~40 cm土层，各序列的ROC₃₃₃、ROC₁₆₇和ROC₃₃与对应序列的SOC的变化势态不一致.在0~40 cm土层，草地序列MBC含量呈先降后升再降势态，各土层MBC最大值均在G15；灌木序列在0~10 cm土层为先升后降再升势态，在10~40 cm土层为先升后降势态；园地序列在0~30 cm土层为先升后降势态，在30~40 cm土层为逐渐升高势态.3个序列K_os大致呈先降后升再降势态，L和LI与K_os相反；CPI呈先升后降势态；草地和园地序列的碳库管理指数（CPMI）呈先升后降势态，而灌木序列CPMI的则呈先升后降再升势态.SOC、ROC₃₃₃、ROC₁₆₇、ROC₃₃和MBC含量及K_os的年增长量大小为：灌木>草地>园地，DOC和CPMI的年增长量大小为：园地>草地>灌木.3个序列SOC及其组分含量均总体随土层增加而降低，具有明显的表聚性.冗余分析结果显示碱解氮（AN）是影响喀斯特地区植被恢复下土壤活性有机碳组分和土壤有机碳库的主要环境因子.综上，土壤活性有机碳组分和CPMI随植被恢复时间发生演变，不同植被恢复均能一定程度地提高喀斯特地区SOC及其组分含量，灌木恢复促进SOC的积累.

Evolution Characteristics of Soil Active Organic Carbon and Carbon Pool Management Index Under Vegetation Restoration in Karst Area

Vegetation restoration affects the carbon cycle of terrestrial ecosystems by changing the rate of carbon input and conversion. In order to explore the evolution characteristics of soil active organic carbon components and carbon pool management index during vegetation restoration in karst areas, the soil of a grassland sequence(5, 10, 15, and 20 a), shrub sequence(5, 10, 15, and 20 a), and garden sequence(5, 10, and 15 a) in a karst area was taken as the research object, and the adjacent farmland was taken as the control(CK). The effects of different vegetation restoration years on the evolution of soil organic carbon(SOC), readily oxidizable organic carbon(ROC₃₃₃, ROC₁₆₇, and ROC₃₃ were all soil active organic carbon that could be oxidized by 333, 167, and 33 mmol·L^-1 KMnO₄), microbial biomass carbon(MBC), dissolved organic carbon(DOC), and carbon pool management index(CPMI) were analyzed. The results showed that compared with that of CK, the average grassland, shrub, and garden SOC contents in the 0-40 cm soil layer increased by 70.77%, 114.40%, and 50.17%, respectively. In the 0-20 cm soil layer, with the increase in restoration years, the SOC content of the grassland sequence and garden sequence increased first and then decreased, and that of the shrub sequence increased first, then decreased, and then increased again. ROC₃₃₃, ROC₁₆₇, and ROC₃₃ were consistent with the SOC change trend of the corresponding sequence. In the 20-40 cm soil layer, the change trend of ROC₃₃₃, ROC₁₆₇, and ROC₃₃ of each sequence was inconsistent with the SOC of the corresponding sequence. In the 0-40 cm soil layer, the MBC content of the grassland sequence decreased first, then increased, and then decreased, and the maximum value of MBC in each soil layer was in G15. The shrub sequence in the 0-10 cm soil layer increased first, then decreased, and then increased, and in the 10-40 cm soil layer it increased first and then decreased. The garden sequence increased first and then decreased in the 0-30 cm soil layer and gradually increased in the 30-40 cm soil layer. K_os of the three sequences decreased first, then increased, and then decreased, whereas L and LI showed the opposite of K_os. CPI increased first and then decreased; the CPMI of the grassland and garden sequences increased first and then decreased, whereas the CPMI of the shrub sequence increased first, then decreased, and then increased again. The contents of SOC, ROC₃₃₃, ROC₁₆₇, ROC₃₃, and MBC and the annual growth of K_os were shrub>grassland>orchard, and the annual growth of DOC and CPMI were orchard>grassland>shrub. The contents of SOC and its components in the three sequences decreased with the increase in soil layer and had obvious surface aggregation. Redundancy analysis showed that alkali-hydrolyzable nitrogen(AN) was the main environmental factor affecting soil active organic carbon components and soil organic carbon pool under the vegetation restoration in the karst area. In summary, soil active organic carbon components and CPMI evolved with vegetation restoration years. Different vegetation restorations could increase the content of SOC and its components in karst areas to a certain extent, and shrub restoration promotes the accumulation of SOC.