Change in Soil Organic Carbon Patterns Across a Large Mixed-Use Landscape in the South-Eastern U.S.

The mosaic of ecosystem components and functions distributed across a landscape represent the combined effects and interactions of a myriad of biotic and abiotic factors including soils, climate, land cover, land use, topography, geology, and human-induced stressors (e.g. climate change or shift in land use management). As a result, existing soil-landscape patterns implicitly contain information about the processes that generated these patterns. Soil carbon patterns and associated soil environmental services must be viewed in the context of interacting forces and feedbacks that stabilize or destabilize a landscape and operate at a variety of spatial and temporal scales inducing carbon sequestration or loss. Our objectives were to (i) assess the spatial patterns of soil organic carbon (SOC) in dependence of various interacting environmental factors, and (ii) investigate the change in SOC across several decades in a large region in the south-eastern U.S.  Large historic (n: 1,099) and current (2008/2009) (n: 1,014) SOC datasets were used to assess SOC change within Florida (~150,000 km²) consisting of agricultural, forest, urban, and natural land uses. Mixed (stochastic/deterministic) models were used to estimate historic SOC and current SOC across the region. A site-specific comparison of about 50% of the resampled historic sites was performed to assess SOC sequestration/losses. Spatially-explicit analyses to assess SOC change between historic SOC estimates and current SOC measurements, and between historic SOC measurements and current SOC estimates, were performed which entailed higher uncertainties. This landscape is extremely rich in historic soil carbon with about 4.110 ± 1.01 Pg C (mean ± std. error) within 1 m profiles accounting for approximately 0.13% of soil C on earth based on estimates of the global soil carbon pool of 3,250 Pg C. SOC change were most pronounced in those areas where multiple biotic and abiotic factors imparted control on soil carbon dynamics.