ALBERT

Description: Variations in speleothem δ 13 C values can reflect changes in overlying surface vegetation, which, over historical time scales, may represent the influence of human activities. Here, we examined δ 13 C variations in two stalagmites growing for the last 2200 years in Shennong Cave, Jiangxi Province, SE China. The two δ 13 C records corroborate well one another and show a prominent 6‰ enrichment of the δ 13 C values from AD 700 to 1100. The isotopic equilibrium for modern calcite and negative correlation between δ 18 O and δ 13 C values along the growth axis suggest that the influences of kinetic fractionation are negligible. Varied correlations between Mg / Ca and Sr / Ca ratios and divergent changes between δ 13 C values and Mg / Ca and Sr / Ca ratios from AD 700 to 1100 reveal that the prior calcite precipitation (PCP) and water–rock interaction did not dominate the increase of δ 13 C values. It is plausible that the obvious δ 13 C variation was largely influenced by the changes in vegetation cover overlying the cave. Our δ 13 C results, together with the records of climate and human activity from historical documentary records, suggest that: (i) prior to AD 700, small fluctuations in relatively light δ 13 C values reflect the presence of lush forest coverage above the cave, which was minimally disturbed by human activities; (ii) during AD 700–1100, the drastic increase in δ 13 C values indicates persistent and massive deforestation associated with large-scale immigration into northern Jiangxi after the Rebellion of An & Shi (AD 755–763) in the Tang Dynasty and the subsequent development of agriculture and economic activity; and (iii) since AD 1100, fluctuations in relatively high δ 13 C values suggest that local vegetation during the last millennium has been sparse. Since the Rebellion of An & Shi , southeastern China was progressively developed, coincident with deforestation and vegetation deterioration caused by human disturbance in the form of deforestation and cultivation.