Abstract: This paper studied the profile distribution characters of ¹³⁷Csand soil organic carbon (SOC) on the Karst slopes and in the fissures in typical peak-cluster depression in Northwest Guangxi, aimed to approach the applicability of ¹³⁷Csmethod on Karst slopes and the implication of ¹³⁷Csfor the characteristics of slope soil erosion. In all test profiles, there was a significant correlation between ¹³⁷Cs and SOC, indicating that both of them might have the same loss pathway. On the slopes under secondary forests, ¹³⁷Cs mainly existed within the depth 0-24 cm. On the upper middle and middle slope sites, ¹³⁷Cs had an exponential decrease with depth, indicating no or slight surface erosion; while on the foot slope site, the distribution pattern of ¹³⁷Cs indicated severer erosion. On the slopes with cultivated lands, ¹³⁷Cs distributed uniformly within the plough layer. In the upper middle and middle slopes profiles, ¹³⁷Cs mainly existed in the depth around 15 cm and far less than the background value, indicating severe soil erosion; while in foot slope profiles, ¹³⁷Cs was aggraded to the depth 45 cm. A discontinuous distribution of ¹³⁷Cs in the profiles was detected on the foot slopes under secondary forests, on the upper middle and foot slopes of cultivated lands, and in the fissures, indicating that the soil particles on Karst slopes had a trend of losing with rainwater to the underground, but the loss quantity was negligible, compared with surface erosion.

Key words: Karst, soil erosion, ¹³⁷Cs, soil organic carbon (SOC), profile distribution