Reducing greenhouse gas emissions via harvest residue management in eucalyptus afforestation on Brazilian sandy soils

Introduction The greenhouse gas balance is a central theme in discussions related to forest ecosystems. In this context, the present study evaluated the impact of five eucalyptus harvest residue management systems on atmospheric C-CO 2 retention in soil, greenhouse gas (GHG) emissions, and the global warming potential (GWP) in Eucalyptus saligna plantations. Methods The management systems examined were: AR - all harvest residues retained on soil; NB - harvest residues kept on soil, except bark; NBr - harvest residues kept on soil, except branches; NR - all harvest residues (bark, branches, leaves) removed; NRs - all residues from the previous rotation and new plantation litter removed using shade cloth. Soil emissions of nitrous oxide (N 2 O) and methane (CH 4 ) were monitored over 12 months (October 2016 to October 2017). Soil samples were collected to a depth of one meter to assess atmospheric C-CO 2 retention. Results and discussion Annual N 2 O emissions were low (0.11–0.23 kg N-N 2 O ha −1 year −1 ) and showed no clear relationship with the amount of nitrogen added through residues. The soil consistently functioned as a methane sink across all management systems, with CH 4 fluxes ranging from –2.56 to –3.91 kg C-CH 4 ha −1 year −1 . The highest rate of C-CO 2 retention in soil (–5,540 kg C-CO 2 ha −1 year −1 ) was observed under the AR management system, while the lowest (–1,752 kg C-CO 2 ha −1 year −1 ) occurred under the NRs system. AR management also resulted in the lowest global warming potential (–33,946 kg C-CO 2 ha −1 year −1 ), primarily due to soil C-CO 2 retention (15.43%) and carbon accumulation in biomass and wood products (84.57%). These findings demonstrate that retaining eucalyptus harvest residues in subtropical sandy soils, in conjunction with carbon sequestration in wood products, constitutes an effective forest management strategy for mitigating global warming.