RESEARCH ARTICLE Spatial Variation in the Storages and Age- Related Dynamics of Forest Carbon Sequestration in Different Climate Zones— Evidence from Black Locust Plantations on the Loess Plateau of China

Knowledge about the long-term influences of climate change on the amount of potential car-bon (C) sequestration in forest ecosystems, including age-related dynamics, remains un-clear. This study used two similar age-sequences of black locust forests (Robinia pseudoacacia L.) in the semi-arid and semi-humid zones of China’s Loess Plateau to as-sess the variation in C stocks and age-related dynamics. Our results demonstrated that black locust forests of the semi-humid zone stored significantly more C than did forests in the semi-arid zone, across the chronosequence (P< 0.001). The C carrying capacity of the plantations was measured at 166.4 Mg C ha−1 (1 Mg = 106 g) in the semi-humid zone, while the semi-arid zone had a capacity of only 79.4 Mg C ha−1. Soil organic C (SOC) increased continuously with stand age in the semi-arid zone (R2 = 0.84, P = 0.010). However, in the semi-humid zone, SOC declined sharply by 47.8 % after the initial stage (5 to 10 y). The C stock in trees increased continuously with stand age in the semi-humid zone (R2 = 0.83, P = 0.011), yet in the semi-arid zone, it decreased dramatically from 43.0 Mg C ha−1 to 28.4 Mg C ha−1 during the old forest stage (38 to 56 y). The shift from being a net C sink to a net