A Continental-Scale Estimate of Soil Organic Carbon Change at NEON Sites and Their Environmental and Edaphic Controls

Current carbon cycle models focus on the effects of climate and land-use change on primary productivity and microbial-mineral dependent carbon turnover in the topsoil, while less attention has been paid to vertical soil processes and soil-dependent response to land-use change along the profile. In this study, a spatial-temporal analysis was used to estimate soil organic carbon (SOC) change in topsoil/A horizon and subsoil/B horizon at National Ecological Observatory Network (NEON) sites, USA over 30 years. To separate the effects of land-use, environmental, and edaphic factors on SOC change, space-for-time substitution was used in combination with the Continuous Change Detection and Classification algorithm and Structural Equation Modeling. Results showed that (a) under natural vegetation, Spodosols and Inceptisols found in the eastern NEON sites had substantial topsoil SOC accumulation (+0.4 to +1.2 Mg C ha(-1) year(-1)), while Inceptisols and Andisols in the west had a comparable magnitude of topsoil SOC loss (-0.5 to -1.8 Mg C ha(-1) year(-1)); (b) Mollisols and Alfisols in the Central Plains sites were susceptible to significant SOC loss under farming and grazing; (c) Runoff/erosion and leaching potential, vertical translocation, and mineral sorption were the most important factors controlling SOC variation across the NEON sites. Our work could be used to parameterize ecosystem models simulating SOC change.

Automated summary

Current carbon cycle models have focused on the effects of climate and land-use change on primary productivity and microbial-mineral dependent carbon turnover in the topsoil, but have overlooked the importance of vertical soil processes and soil response to land-use change along the profile. In this study, spatial-temporal analysis was used to estimate soil organic carbon (SOC) change at NEON sites in the USA over 30 years. The study found that different soil types and land-use practices had significant impacts on SOC accumulation or loss, and identified runoff/erosion, leaching potential, vertical translocation, and mineral sorption as the key factors controlling SOC variation.