A multiple-proxy stalagmite record reveals historical deforestation in central Shandong, northern China

Evaluating anthropogenic impacts on regional vegetation changes during historical time is not only important for a better understanding of the Anthropocene but also valuable in improving the vegetation-climate models. In this study, we analyzed stable isotopes (δ¹⁸O, δ¹³C) and trace elements (Mg/Ca, Sr/Ca) of a stalagmite from Huangchao Cave in central Shandong, northern China. ²³⁰Th and AMS¹⁴C dating results indicate the stalagmite deposited during 174BC and AD1810, with a hiatus between AD638 and 1102. Broad similarities of the δ¹⁸O and trace elements in the stalagmite suggest they are reliable precipitation indexes. The δ¹³C of the stalagmite, a proxy of vegetation change, was generally consistent with local precipitation and temperature variations on a centennial-scale before the 15th century. It typically varied from −9.6‰ to −6.3‰, indicating climate controlled C3 type vegetation during this period. However, a persistent and marked increasing trend in the δ¹³C record was observed since the 15th century, resulting in δ¹³C values from −7.7‰ to −1.6‰ in the next four centuries. This unprecedented δ¹³C change caused by vegetation deterioration cannot be explained by climate change but is fairly consistent with the dramatically increasing population and farmland in Shandong. We suggest that the increasing deforestation and reclamation in central Shandong began to affect vegetation in the mountain region of central Shandong since the 15th century and severely destroyed or even cleared the forest during the 16th–18th century.