Depth assessed and up-scaling of single case studies might overestimate the role of C sequestration by pastures in the commitments of Brazil's low-carbon agriculture plan

摘要

The reclamation of degraded pastures has a prominent role in the Brazilian climate policy and is one of the main strategies of Brazil's Low-Carbon Agriculture Plan (ABC Plan). Here, we aimed to evaluate the changes in soil C and N stocks in livestock areas under pasture reclamation and contribute to the empirical basis for evaluating the ABC Plan. Based on the assessment of six chronosequences across Brazilian Cerrado, we observed that the effects of management practices for pasture reclamation on soil C and N stocks in livestock areas were quite variable. Any general tendencies depend on the depth evaluated. At the 0-30 cm soil layer, pasture areas under reclamation in Brazilian Cerrado showed an average soil C change rate of 0.47 Mg C ha(-1 )yr(-1). However, for the more in-depth assessment (0-100 cm), the adoption of management practices for pasture reclamation did not affect the average rate of soil C changes for these areas. In this sense, we suggest that an up-scaling from single case studies may lead to overestimations of soil C inventories. Thefore, ABC Plan must review some of its approaches based on general values and extrapolations regarding C sequestration in pasture areas.