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

Abstract

In karst landscapes, soil CO 2 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 CO 2 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 CO 2 transfer characteristics and source-sink effects. The results showed similar average soil respiration rates between calcareous soil and red soil, with an average CO 2 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. CO 2 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 CO 2 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 CO 2 .

Spatial heterogeneity and scenario simulation of carbon budget on provincial scale in China

“…Chinese scholars have mainly conducted studies at the national [ 15 ], provincial [ 16 ], and municipal [ 17 ] levels. As for the carbon budget of different land use types, many studies have been conducted on individual land use types such as forestland [ 18 , 19 ], grassland [ 20 ], water land [ 21 ], and built-up land [ 22 ]. Based on the study of the carbon budget, researchers have conducted analysis of the influencing factors, with the decomposition of influencing factors mainly focused on carbon emissions.…”

Spatial-Temporal Evolutionary Characteristics of Shellfish and Algae Carbon Sinks in China: Analysis Based on Geographic Information System (GIS)

“…Carbon sinks in ecosystems include forests, oceans, grasslands, wetlands, soils, permafrost, and karst habitats [6,7]. Compared with other sources, oceans fix 55% of global carbon and absorb about 20%-35% of carbon emissions from human activities every year, which can be stored for hundreds or even thousands of years [8,9].…”

Evaluation of Five Gas Diffusion Models Used in the Gradient Method for Estimating CO2 Flux with Changing Soil Properties

“…Soil respiration may constitute up to about three-quarters of total ecosystem respiration, which has an important impact on the global carbon cycle and climate change [1,2]. Therefore, soil carbon dioxide (CO 2 ) emissions have received much attention [3,4]. Currently, the most widely used soil CO 2 flux measuring methods are the micro-meteorological eddy covariance method [5][6][7], the chamber method [8][9][10] and the gradient method [11][12][13].…”