Scale-dependent variability of soil organic carbon coupled to land use and land cover

Abstract

Understanding the field-scale spatial variability of soil organic carbon (SOC) is critical to assess its spatial distribution at very fine scale (several meters) which is valuable for precision agriculture and natural resource management. The aim of this study was to investigate the field-scale spatial variability of SOC under five prevalent land use and land cover (LULC) types in Florida, U.S. with a uniform sampling scheme. Five scales, 2, 7, 22, 67 and>200m, were targeted and 108 soil samples at 0–20cm depth were collected and analyzed for SOC and bulk densities within each LULC type in 2012. Results indicate that SOC variability was scale dependent. Hardwood Hammock and Forest and Improved Pasture demonstrated large variation at both coarse scale (67 and>200m) and very fine scale (2m). Sandhill, Pineland and Dry Prairie were dominated by variation at very fine scales (2 and 7m). All five sites showed large variability at very fine scales, indicating the close coupling of SOC stock variation to structure and composition of vegetation. This study also identified that log-transformed SOC showed variance-invariant behavior, which had an approximately constant overall variance (sill) of 0.067±0.012 (log(kgm−2))2at field scale (∼500m) irrespective of LULC. These findings serve to explain field-scale variability of SOC relevant for precision agriculture and land management, but also facilitate better understanding of the scale-dependent fine-scale variability of SOC across larger soilscapes.