Contributions of soil organic carbon and inorganic carbon stocks to total soil carbon stock and their driving factors across different types in Nei Mongol temperate grasslands

doi:10.17521/cjpe.2024.0443

Abstract

Abstract:

Aims As a key component of terrestrial ecosystem carbon pools, soil carbon storage in grasslands, encompassing both soil organic carbon (SOC) and soil inorganic carbon (SIC) pools, plays a crucial role in terrestrial carbon cycling and climate feedback. However, current research has primarily focused on SOC dynamic, while the regulatory mechanisms governing the storage of both SOC and SIC remain poorly understood. The comprehensive understanding of soil carbon storage, including its composition and spatial distribution across different grassland types, is still lacking.
Methods Here, we conducted a field survey in temperate grasslands of Nei Mongol, selecting two grassland types: typical steppe and meadow steppe. We measured soil physicochemical properties, plant biomass and chemical traits, as well as microbial biomass carbon and community composition. Based on these data, we applied boosted regression trees and structural equation modeling to investigate the relative importance of the four explanatory factors—climatic, edaphic, vegetational, and microbial variables, in shaping total soil carbon storage and its organic and inorganic components. Additionally, we explored the mechanisms underlying their influence.
Important findings This study found that the SIC stock in the 0-60 cm soil layer of typical steppe ((2.75 ± 0.15) kg C·m^-2) was significantly higher than that in meadow ((0.45 ± 0.03) kg C·m^-2), while there was no significant difference in soil organic carbon storage ((8.61 ± 0.19) kg C·m^-2 for typical steppe and (8.32 ± 0.17) kg C·m^-2 for meadow), resulting in a significantly higher total soil carbon storage in typical grasslands compared to meadow grasslands. The SOC content of both grassland types decreased with soil depth. However, the SIC content in typical steppe exhibited pronounced accumulation in deeper soil layers, a pattern that was absent in meadow. Biotic and abiotic factors, including vegetation characteristics, climate, and soil properties, jointly influenced total soil carbon and its SOC and SIC components, with distinct regulatory mechanisms between grassland types. In typical steppe with strong water limitations, soil carbon storage was primarily regulated by climate factors, whereas in meadow steppe with relatively higher moisture availability, soil properties played a more prominent role. These findings provide a scientific basis for accurately assessing the soil carbon storage in temperate grasslands and enhance our understanding of the distribution mechanisms of soil carbon under multi-factor interactions.

Key words: temperate grasslands, soil carbon stock, soil carbon fractions, organic-inorganic carbon coupling, climate-plant-soil interactions

CHANG Peng-Fei, LI Ping, Nairsag , WANG Jing, WANG Zhen-Hua, YANG Sen, JIA Zhou, YANG Lu, LIU Ling-Li, DENG Mei-Feng. Contributions of soil organic carbon and inorganic carbon stocks to total soil carbon stock and their driving factors across different types in Nei Mongol temperate grasslands[J]. Chin J Plant Ecol, 2025, 49(9): 1374-1387.

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URL: https://www.plant-ecology.com/EN/10.17521/cjpe.2024.0443

https://www.plant-ecology.com/EN/Y2025/V49/I9/1374

Figures/Tables 5

Fig. 1 Impacts of grassland types and climatic variables on soil carbon stocks. SIC, soil inorganic carbon; SOC, soil organic carbon. A, Impacts of grassland types on total soil carbon and its organic and inorganic component stocks (mean ± SE). B, C, Impacts of mean annual precipitation (MAP) on soil organic and inorganic carbon stocks in different grassland types. D, E, Impacts of mean annual air temperatures (MAT) on soil organic and inorganic carbon stocks in different grassland types. Different uppercase letters in A indicate that significant differences in total soil carbon stock between grassland types (p < 0.05); different lowercase letters indicate significant differences between grassland types within the SOC or SIC (p < 0.05). Solid lines in B-E represent significant relationships (p < 0.05).

Fig. 2 Changes of the soil carbon content along the soil profile across different grassland types (mean ± SE). The significant sign in A-C indicate that there are significant differences in soil carbon content between typical steppe and meadow at different soil depths (·, p < 0.1; *, p < 0.05; **, p < 0.01; ***, p < 0.001).

Fig. 3 Impacts of soil (A, B), plant (C-F), and microbial (G-H) properties on total soil carbon stocks across different grassland types. Solid lines represent significant relationships (p < 0.05). C:N, carbon to nitrogen ratio; F:B, fungi to bacteria ratio.

Fig. 4 Relative influence of different factors on total soil carbon stocks in typical steppe and meadow steppe. Al, aluminum; C:N, carbon to nitrogen ratio; Ca, calcium; DIN, dissolved inorganic nitrogen; F:B, fungi to bacteria ratio; Fe, iron; MAP, mean annual precipitation; MAT, mean annual air temperature; MBC, microbial biomass carbon content; Mn, manganese; P, phosphorus.

Fig. 5 Direct and indirect drivers of soil carbon stocks in the grassland. Grassland types, climate, plant, soil, and microbial properties were divided into composite variables. Numbers at arrows are standardized path coefficients. Arrow thickness represents the strength of the relationships (*, p < 0.05; **, p < 0.01; ***, p < 0.001). Red arrows indicate significant positive relationships and black arrows indicate significant negative relationships (p < 0.05). Dashed arrows represent nonsignificant relationships (p ≥ 0.5). C:N, carbon to nitrogen ratio; F:B, fungi to bacteria ratio; MAP, mean annual precipitation; MAT, mean annual air temperature; MBC, microbial biomass carbon content. AIC, Akaike information criterion; RMSE, root mean square error.

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