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Open AccessArticle

CO2 Transfer Characteristics of Calcareous Humid Subtropical Forest Soils and Associated Contributions to Carbon Source and Sink in Guilin, Southwest China

by Fen Huang 1,2, Jianhua Cao 1,2,*, Tongbin Zhu 1,2, Mingzhu Fan 1,2 and Mengmeng Ren 1,3
1
Key Laboratory of Karst Dynamics, Institute of Karst Geology (CAGS), Ministry of Natural Resourses (MNR) and Guangxi, Guilin 541004, China
2
International Research Center on Karst, Under the Auspices of United Nations Educational, Scientific and Cultural Organization (UNESCO), Guilin 541004, China
3
School of Water Resources and Environment, China University of Geosciences (Beijing), Beijing 100083, China
*
Author to whom correspondence should be addressed.
Forests 2020, 11(2), 219; https://doi.org/10.3390/f11020219
Received: 4 January 2020 / Revised: 7 February 2020 / Accepted: 11 February 2020 / Published: 14 February 2020
In karst landscapes, soil CO2 is a key factor in weathering processes and carbon cycling, where its distribution and migration characteristics directly affect fluxes in carbon source–sink dynamics. We measured the CO2 emission and dissolution rates of carbonate tablets in calcareous soil developed from limestone and red soil developed from clastic rock, in karst and non-karst subtropical forests, in Guilin, southwest China between 2015 and 2018, to analyze their CO2 transfer characteristics and source–sink effects. The results showed similar average soil respiration rates between calcareous soil and red soil, with an average CO2 emission flux of 1305 and 1167 t C km−2 a−1, respectively. Carbonate tablet dissolution rates were bidirectional with increasing depth and were greater in red soil than calcareous soil, averaging 13.88 ± 5.42 and 7.20 ± 2.11 mg cm−2 a−1, respectively. CO2 concentration was bidirectional with increasing soil depth, reaching a maximum at the base of the soil–atmosphere interface (50–60 cm), and the bidirectional gradient was more distinctive in red soil. Change in the carbon isotope value of soil CO2 was also bidirectional in calcareous soils, for which the overall average was 0.87‰ heavier in calcareous than red soil. The carbon sink in calcareous soil in karst regions was estimated to be 11.97 times that of red soil in non-karst regions, whereas its role as a carbon source is just 1.12 times that of red soil, thus indicating the key role of karst soil in the reduction of atmospheric CO2. View Full-Text
Keywords: subtropical forest; calcareous soils; red soils; soil CO2; carbon source–sink subtropical forest; calcareous soils; red soils; soil CO2; carbon source–sink
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Huang, F.; Cao, J.; Zhu, T.; Fan, M.; Ren, M. CO2 Transfer Characteristics of Calcareous Humid Subtropical Forest Soils and Associated Contributions to Carbon Source and Sink in Guilin, Southwest China. Forests 2020, 11, 219.

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