Impacts of Bedrocks on Vegetation Carbons in Typical Karst Areas: A Case Study in Puding County, Southwest China

An accurate estimation of vegetation carbon pools and their carbon sequestration potential is significant in global carbon cycle research but the existing estimations are still insufficient and largely uncertain. Here, we estimated the vegetation carbon density, carbon stocks, and carbon sequestration potential under three main bedrock types (limestone, dolomite, and non-carbonate) in Puding County, Guizhou Province, Southwestern China. The data used here included high-resolution vegetation maps of Puding, data from 274 sample plots, and the carbon contents measured previously in adjacent areas. The land area ratio of natural vegetation at an early stage (namely, grassland and shrub, excluding artificial forests and cultivated land) in carbonate rock areas is significantly larger than that in non-carbonate areas. The average existing carbon densities of vegetation in the non-carbonate, limestone, and dolomite areas were 31.59 +/- 7.43, 16.75 +/- 4.12, and 8.26 +/- 2.45 Mg<middle dot>ha-1, respectively, while their existing carbon stocks were 752.37 +/- 172.85, 855.69 +/- 210.65, and 208.49 +/- 61.82 Gg, respectively. The maximum vegetation carbon densities of mature forests in the three bedrock types were 156.49 +/- 12.92, 130.27 +/- 6.05, and 117.41 +/- 30.03 Mg<middle dot>ha-1, respectively. Then, their average vegetation carbon sequestration potentials were 56.07 +/- 23.06, 70.13 +/- 11.39, and 59.11 +/- 33.00 Mg<middle dot>ha-1, respectively. In other words, vegetation carbon stocks in the non-carbonate, limestone, and dolomite areas increased by 1.34 +/- 0.42, 3.58 +/- 0.48, and 1.49 +/- 0.51 Tg, respectively, after continuous evolution to mature forests. In conclusion, the potential growth of carbon density for karst vegetation is slightly higher than that of non-karst vegetation, despite its lower existing carbon density. Additionally, natural vegetation has a greater potential for carbon sequestration than plantations on all three bedrock types.