Soil Organic Carbon in Pampean Agroecosystems: Horizontal and Vertical Distribution Determined by Soil Great Group

Abstract

Different soil types have a substantial impact on many of the processes that take place in ecosystem functioning and thus in soil organic C (SOC) stocks. Knowledge of the C pool in different soil taxa and its vertical distribution is necessary since very few studies have compared SOC stocks by horizon and depth increment. Buenos Aires province, Argentina is an interesting area to characterize temperate system SOC stocks and may be used as a model system for temperate lands across the globe. The objectives of this study were to (i) quantify SOC content and vertical distribution (0–100 cm) at the great group level in Buenos Aires province and (ii) identify relationships between the distribution of SOC and edaphic properties. The analysis presented here is based on 248 soil profiles. Major soil great groups included were Argiudolls, Hapludolls, Natraquolls, and Haplustolls. Soil organic C (kg m−2) was estimated for each soil taxa and profile (0–1 m depth). Argiudolls contained the most SOC in the first two horizons (A and B) compared with other soil groups. The mean content of total SOC (0–30 and 30–100 cm) for the Argiudolls was significantly greater than in all other soil great groups; Natraquolls had the least. The SOC followed a general pattern of gradually decreasing with depth, with A and B horizons the major contributors to SOC storage in the region. The main contributors to SOC storage at the 0- to 100-cm depths were Argiudolls (with 220 Gg) and Hapludolls (with 215 Gg). Sand, clay, and N contents were correlated to SOC content in all the great groups. A division in organic carbon storage between the major soil groups in this province of the Pampas Region was possible and may be useful to compare fluxes of SOC at regional and global scales.