Gustavo V. Popina, 1, Maria Eduarda B. de Resendec, 2, Jorge L. Locatellia, 3, Rafael S. Santosd, 4, Marcos Siqueira-Netoe, 5, Paulo M. Brandof, g, 6, Christopher Neillh, 7, Carlos E.P. Cerria, b, 8
a Department of Soil Science, “Luiz de Queiroz” College of Agriculture – University of São Paulo, Avenida Pádua Dias, 11, Piracicaba, SP 13418-260, Brazil
b Center for Carbon Research in Tropical Agriculture (CCARBON) – University of São Paulo, Avenida Pádua Dias 11, Piracicaba, SP 13418-900, Brazil
c Centro de Energia Nuclear na Agricultura – University of São Paulo, Avenida Centenário, 303, Piracicaba, SP 13400-970, Brazil
d Natural Resource Ecology Laboratory, Colorado State College, Fort Collins, CO 80523, USA
e Biofílica Ambipar Environmental, Avenida Angélica, 2330, São Paulo, SP 01228-200, Brazil
f Yale School of the Environment, Yale University, 195 Prospect St., New Haven, CT 06511, USA
g Yale Center for Natural Carbon Capture (YCNCC) – Yale University, PO Box 208109, New Haven, CT 06520, USA
h Woodwell Climate Research Center, 149 Woods Hole Road, Falmouth, MA 02540-1644, USA
b Center for Carbon Research in Tropical Agriculture (CCARBON) – University of São Paulo, Avenida Pádua Dias 11, Piracicaba, SP 13418-900, Brazil
c Centro de Energia Nuclear na Agricultura – University of São Paulo, Avenida Centenário, 303, Piracicaba, SP 13400-970, Brazil
d Natural Resource Ecology Laboratory, Colorado State College, Fort Collins, CO 80523, USA
e Biofílica Ambipar Environmental, Avenida Angélica, 2330, São Paulo, SP 01228-200, Brazil
f Yale School of the Environment, Yale University, 195 Prospect St., New Haven, CT 06511, USA
g Yale Center for Natural Carbon Capture (YCNCC) – Yale University, PO Box 208109, New Haven, CT 06520, USA
h Woodwell Climate Research Center, 149 Woods Hole Road, Falmouth, MA 02540-1644, USA
Highlights
- The soil C stocks to 800 cm ranged from 168.4 Mg ha−1 to 288.3 Mg ha−1.
- The top 100 cm contained approximately 30–40 % of the carbon stock within the 800 cm depth.
- About 50 % of all soil carbon stocks were concentrated in the 0–300 cm depth, regardless of soil texture.
- Soil carbon between 300 and 800 cm was relatively uninfluenced by land use.
- Soil carbon response to land use and intensification varied with depth: high certainty (0–100 cm), moderate certainty (100–200 cm), and low certainty (>300 cm).
Abstract
Land-use change and agricultural intensification drive the widespread and relatively rapid decline of carbon (C) stocks in surface soils of the Amazon-Cerrado transition region of Brazil. However, less is known about C changes in deep-soil profiles. To understand the carbon dynamics in deep soils affected by land-use change and agricultural intensification, we sampled soil up to 800 cm beneath native forest (NV), minimum tillage soybean (S), soybean-maize (SM) cropland, old pasture (OP), and recently deforested land (RD) that was maintained as cleared but not cropped. All sampling took place at Fazenda Tanguro in Mato Grosso, Brazil. We determined soil C concentrations, mineral-associated organic matter (MAOM), particulate organic matter (POM), δ13C, and water-extractable C (WEC). Soil C stocks to 800 cm ranged from 168.4 Mg ha−1 to 288.3 Mg ha−1. Regardless of the land use, the top 100 cm contained 30–40 % of the C stock to 800 cm, and about 50 % of all soil C stocks was concentrated until 300 cm. Conversion of forest to no-till single-cropping soybean negatively impacted soil C until 100 cm through reduction of MAOM stocks. The WEC concentrations were highest at the surface and decreased with depth. The RD showed the lowest WEC concentrations in the topsoil layer. Production intensification on the cropland led to superficial soil C accrual. Pasture showed great potential to store C through POM inputs on subsoil. This study provides important insights into the dynamics of carbon profiles in deep soils following land-use change and agricultural intensification. Thus, we can highlight: 1) Removal of native vegetation promotes rapid changes in surface C dynamics (less than 100 cm), consequently impacting C pools up to at least 300 cm in depth; 2) Intensification through double cropping has the potential to promote the restoration of these productive C pools over time; 3) as expected, soil C storage is closely related to clay content. Finally, based on these findings, we recommend that studies related to the impacts of agricultural expansion and intensification on the dynamics of soil C pools should focus efforts on sampling at least 100 cm deep in the soil, with stratified collections each 10 cm in the surface layers (up to 50 cm), and extend it to at least 300 cm, considering more areas, soil types, soil attributes, and land uses.
Keywords
Soil organic matter, Tropical conditions, Subsoil carbon, Agricultural intensification
