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

• Main Authors: N. A. Osinaga, C. R. Álvarez, M. A. Taboada
• Format: Article
• Language: English
• Published: Copernicus Publications 2018-11-01
• Series: SOIL
• Online Access: https://www.soil-journal.net/4/251/2018/soil-4-251-2018.pdf

<p>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&thinsp;m depth in soils under different land use:  &lt; 10-year continuous cropping,  &gt; 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&thinsp;m depth expressed as equivalent mass varied as follows: forest (119.3&thinsp;Mg&thinsp;ha⁻¹)&thinsp; &gt; &thinsp;pasture (87.9&thinsp;Mg&thinsp;ha⁻¹)&thinsp; &gt; &thinsp;continuous cropping (71.9 and 77.3&thinsp;Mg&thinsp;ha⁻¹), with no impact of the number of years under cropping. The coarse particle fraction (2000–212&thinsp;µm) at 0–5 and 5–20&thinsp;cm depth layers was the most sensitive organic carbon fraction to land use change. Resistant carbon ( &lt; 53&thinsp;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&thinsp;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.</p>