Reconstructing 60-year soil organic carbon storage in karst watersheds in Southwest China

Cao, Zihao, Zhang, Keli, Chappell, Adrian ORCID: https://orcid.org/0000-0002-0694-7348, Zhang, Zhuodong, Zhou, Zhuoli, Xiao, Shizhen, He, Jianghu and Cao, Yang 2025. Reconstructing 60-year soil organic carbon storage in karst watersheds in Southwest China. CATENA Item availability restricted.

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Abstract

Soil organic carbon (SOC) dynamics in fragile karst ecosystems critically influence global carbon budgets but remain poorly quantified, particularly regarding deep sediment archives. This study pioneers high-resolution analysis of depression sediment profiles to reconstruct 60 years of SOC storage (SOCS) dynamics in Southwest China’s karst watersheds. Using sediment core analysis and ¹³⁷Cs dating across three peak-cluster depressions (SJP, DJT, CZ), we: (1) characterized vertical SOC distribution, (2) quantified historical SOCS changes, and (3) established land use impacts through a vegetation succession framework. The results showed that sediment profiles in the SJP, DJT and CZ depressions exhibited consistent vertical SOC distribution. Peak concentrations were observed in the topsoil, gradually decreasing with depth and eventually stabilized in deeper layers. However, spatial heterogeneity was pronounced. DJT and CZ showed higher mean SOC with lower variability, contrasting sharply with SJP’s lower SOC and higher variability. Crucially, SOC density (SOCD) trajectories diverged temporally. SJP transitioned from high early growth (222% pre-1954) to near-zero accumulation post-1963, while DJT and CZ reversed negative trends (-60.2% and -53.6%) to strong positive growth (124.4% and 6.5%). Cumulative SOCS over the past 60 years reached 100.4 t (SJP), 57.8 t (DJT), and 3.9 t (CZ), dominated by legacy carbon (70–79% of 0–200 cm deep pools). Quantification of vegetation succession effects showed that agricultural expansion (forest/shrubs and grassland to cropland) reduces SOC deposition rates by 78–85%, and ecological restoration (cropland to forest/shrubs and grassland) increases rates by 350–550%. Despite the time-lagged nature of SOC accumulation, this study demonstrated that ecological restoration significantly enhances carbon sink potential in karst watersheds. Collectively, this work advanced the understanding of SOC dynamics in karst systems, offering empirical evidence for optimizing land management to balance agricultural development and ecological restoration. Keywords: Soil organic carbon (SOC) profiles, Soil organic carbon storage (SOCS), ¹³⁷Cs dating, Sediment deposition, Karst peak-cluster depression

Item Type:	Article
Status:	In Press
Schools:	Schools > Earth and Environmental Sciences
Publisher:	Elsevier
ISSN:	0341-8162
Date of First Compliant Deposit:	9 September 2025
Date of Acceptance:	5 September 2025
Last Modified:	10 Sep 2025 14:15
URI:	https://orca.cardiff.ac.uk/id/eprint/181022

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