Effect of deforestation and subsequent land use management on soil carbon stocks in the South American Chaco

• Published in: Soil Vol. 4; no. 4; pp. 251 - 257
• Main Authors: Osinaga, Natalia Andrea, Álvarez, Carina Rosa, Taboada, Miguel Angel
• Format: Journal Article
• Language: English
• Published: Göttingen Copernicus GmbH 01.11.2018; Copernicus Publications
• Subjects: Carbon; Continuous cropping; Cropping systems; Deforestation; Depth; Forests; Grasses; Land management; Land use; Land use management; Organic carbon; Organic matter; Organic soils; Pasture; Preservation; Soil; Soils; Stocks; Sustainable use; Chaco region
• ISSN: 2199-398X; 2199-3971; 2199-398X; 2199-3971
• DOI: 10.5194/soil-4-251-2018

The subhumid Chaco region of Argentina, originally covered by dry sclerophyll forest, has been subjected to clearing since the end of the 1970s and replacement of the forest by no-till farming. Land use changes produced a decrease in aboveground carbon (C) stored in forests, but little is known about the impact on soil organic C stocks. The aim of this study was to evaluate soil C stocks and C fractions up to 1 m depth in soils under different land use: <10-year continuous cropping, >20-year continuous cropping, warm-season grass pasture and native forest in 32 sites distributed over the Chaco region. The organic C stock content up to 1 m depth expressed as equivalent mass varied as follows: forest (119.3 Mg ha−1) > pasture (87.9 Mg ha−1) > continuous cropping (71.9 and 77.3 Mg ha−1), with no impact of the number of years under cropping. The coarse particle fraction (2000–212 µm) at 0–5 and 5–20 cm depth layers was the most sensitive organic carbon fraction to land use change. Resistant carbon (<53 µm) was the main organic matter fraction in all sample categories except in the forest. Organic C stock, its quality and its distribution in the profile were responsive to land use change. The conversion of the Chaco forest to crops was associated with a decrease of organic C stock up to 1 m depth and with the decrease of the labile fraction. The permanent pastures of warm-season grasses allowed higher C stocks to be sustained than cropping systems and so could be considered a sustainable land use system in terms of soil C preservation. As soil organic C losses were not restricted to the first few centimetres of the soil, the development of models that would allow the estimation of soil organic C changes in depth would be useful to evaluate the impact of land use change on C stocks with greater precision.