Organic Carbon Storage in Soils of Tropical and Subtropical China

Abstract

Tropical and subtropical China occupies a total area of about215 Mha, but the contents and storage of soil organic carbon (C)on this land have not been well studied. This research wasconducted in this concern by jointly using soil survey data andthe regional soil map. It was estimated that the 0–20 cm Cdensity of the soil subgroups in the region varied from 1.2 to9.7 kg C m-2. In the major zonal soils, soil subgroup`young ∼' had generally a C density about 1.2–4.4 timeslower than its other natural counterparts. Furthermore, subgroups of thecultivated soil gave a C density about 20–63% lower than theirnatural counterparts (except subgroup `young ∼'), showingremarkable C losses caused by cultivation. For soil groups inthe east, brown soil had the highest C density (6.8 and 21.4 kgC m-2, for the upper 20 and 100 cm soil, respectively),followed by yellow soil, yellow brown soil and limestone soil (4.6–5.5 and 12.3–14.5 kg C m-2, idem). Torrid red soil, purplishsoil and fluvo-aquic soil had the lowest C density (2.0–2.2 and5.8–7.5 kg C m-2, idem) with the others ranking at amedium level. In the west, podzolic soil ranked the highest(17.9 and 55.8 kg C m-2, idem), followed by dark brownsoil, brown soil and limestone soil (6.9–11.6 and 21–29 kg Cm-2, idem), and again torrid red soil, purplish soiland fluvo-aquic soil ranked the lowest (3.9–5.1 and 11.4–14.1 kg C m-2, idem). Finally, a total of about 26.8±7.4 Pg organic C was estimated being stored in soils of the entire region.