Data for Quantitative estimation of shell carbon deposition in terrestrial mollusks in northern China over 20,000 years

To obtain updated data on the modern distribution of carbon storage in mollusk shells, we conducted a study that involved sampling 382 sites across a ~1000 km climatic gradient in northern China. These sites were chosen based on their representation of main topography, land-uses and vegetation types, and were evenly distributed in space. The sampling involved four 0.5m× 0.5m subplots, and individual mollusks were selected using a visual search and extraction from a 3–5 cm-thick sample of litter and soil at each site. Carbon contributes 12g for every 100g of shell, or 12% of overall shell mass. The shells were then weighed, and the carbon content of carbonate deposition through mollusk shell development (CDMS) was calculated using the formula CDMS = (W×95%×12%)/10, where W is the shell weight in grams per square meter in each modern soil sample. This calculation takes into account the amount of carbon deposited, which is 12% of 1g of shell carbonate, and converts the weight from grams per square meter to grams per square meter per year.