Abstract: Taking two Chinese prickly ash orchards (35 and 14-year-old, respectively) in the karst mountain region of southwest Guizhou as test objects, and using the dryland as the control, we studied the changes of waterstable aggregates and organic carbon in surface soil (0-20 cm), and discussed the response of soil organic carbon turnover to ages of Chinese prickly ash plantation. The contents of soil waterstable aggregates presented in an inverted ‘V’shaped distribution with the decreasing soil aggregate size in two plantation ages, and the distribution of soil waterstable aggregates was dominant in 5-2, 2-1, and 1-0.5 mm sizes. Compared with the dryland, organic carbon and readily oxidizable organic carbon in whole soil and different aggregates increased significantly in Chinese prickly ash plantations, being highest in the 14 years old Chinese prickly ash plantation, while an obvious decrease trend was found in the 35 years old plantation. With the increasing age of the plantations, cumulative mineralization of soil organic carbon decreased, but the soil organic carbon turnover was significantly longer in the 14 years old Chinese prickly ash plantation as compared with the dryland and the 35 years old Chinese prickly ash plantation, indicating that soil organic carbon was easier to accumulate in the 14 years old Chinese prickly ash plantation. After planting Chinese prickly ash in the karst region, the soil played a role of carbon sink at early stage, but transformed into carbon source thereafter. Therefore, we suggested that attention should be paid to long-term maintenance and management of Chinese prickly ash plantations to prevent soil quality decline in karst regions.

Key words: species distribution model, statistical model, marine species, model evaluation, mechanism model