Navegando por Autor "Teixeira, Rafael da Silva"

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Above and below ground plant inputs and soil organic matter cycling in an eucalypt plantation in the cerrado biome
(Universidade Federal de Viçosa, 2017-09-27) Teixeira, Rafael da Silva; Silva, Ivo Ribeiro da; http://lattes.cnpq.br/3970484145234987
Soil organic matter (SOM) plays key roles on high productive agrosystems, further may offer an alternative to reduce soil CO 2 -C emissions and improve soil C sequestration. In Brazil, most of the Cerrado (Brazilian Savannah) were initially converted to pastures using unsustainable practices, which promoted soil degradation, soil organic carbon (SOC) stocks losses and increase in GHG emissions. Thus, the conservation land-management systems that favor the input of aboveground and belowground plant residue-C to soil may reduce the impacts caused by land-use change. Because eucalypt trees are fast-growing, they are attractive for C sequestration (aboveground and belowground) and subsequent C input to the soil. So, eucalypt plantation may sequester C in compartments with different timescales: i) Plant biomass and ii) Soil organic matter (SOM). So, this thesis aimed to study the C and N dynamics, focusing in the processes that underline CO 2 -C emissions in on eucalypt plantation since the land-use change following a pasture, until 4-years-old. We report our research in three chapters, aimed at understanding some research gaps. In the first chapter we analyzed the changes in C and N stocks, CO 2 -C and CH 4 -C fluxes in Cerrado, pasture (cultivated for 34-years following the clearing of the Cerrado) and eucalypt (cultivated for 4 years following the pasture). The soil surface CO 2 -C, CH 4 -C fluxes and also CO 2 -C concentration along the vertical soil profile were measured in different seasons (Wet and Dry) over three years. It was also determined the C and N stocks associated to the particulate organic matter (POM) and mineral-associated organic matter (MAOM). Variation in natural abundance of 13 C (δ 13 C) was used to partition the SOM in old (Cerrado- or pasture-derived) and their replacement by the new input C (eucalypt-derived). It was observed that the wet season had the strongest influence on soil surface CO 2 -C and CH 4 -C fluxes, and CO 2 -C concentration at soil depths for the different land uses. The soil under eucalypt plantation emitted ~70% more CO 2 -C than those under Cerrado and pasture after 40-months of eucalypt planting, while the pasture soil emitted more CH 4 -C to the atmosphere than those under Cerrado and eucalypt in Sep 2012, Jan 2013 and Oct 2015. The old MAOM-C losses in deep soil layers were not compensated by the new eucalypt C inputs, resulting in net soil C losses. Nevertheless, no differences were detected to POM-C and -N in the soil (0.0-1.0 m), perhaps indicating a recovery in SOM in eucalypt stands at a more advanced stand age. In the second chapter, we investigated de dynamics of CO 2 -C components in soil surface and soil profile, also tracking the influence of eucalypt root growth (especially fine roots) on these processes. Due historical use was possible partition the soil surface CO 2 -C flux and the CO 2 -C concentration in depth in CO 2 -C plant-derived and CO 2 -C soil-derived. In addition, the root priming effect was calculated. The evaluations were carried out in six seasons: 3, 7, 15, 19, 31 and 40-month-old eucalypt. After the implantation of eucalypt forests there was an increase in soil surface CO 2 -C flux along plant growth (4.33 kg ha -1 h -1 in 40 month-old eucalypt). The root growth contributes greatly to the soil surface CO 2 -C flux (correlated at p<0.01; r: 0.61) promoting the surface RPE over time (correlated at p<0.01; r: 0.63). The moisture has greater influence in the decomposition of litterfall (correlated at p<0.01; r: 0.70) and root respiration and/or rhizodeposition decomposition (correlated at p<0.01; r: 0.79). Finally, in the third chapter we accessed the biomass C storage (Leaves, branches, barks, woods, fine roots, medium roots and coarse roots) and C storage in different SOM pools (POM and MAOM) over time. Eucalypt forest at 36-months-old allocated 72.01 Mg ha -1 of C, with 41.5% being directed to the roots (29.92 Mg ha -1 of C). After 49-months of planting there were mineralization in POM-, MAOM-Cerrado and Pasture, providing an estimated N mineralization of 0.535 Mg ha -1 in the 0.0-1.0-m layer. In contrast, the root-derived C imputed to soil was more efficient in soil organic matter formation (58% higher) than the litterfall- + root-derived C imputed to soil. After 49-months of eucalypt planting the forest was not a potential sequestration of C (ΔC Soil : -2.22 Mg ha -1 ) to 0.0-1.0 m soil layer. However, studies with longer time scales are required for completeness of information about potential of CO 2 -C sequestering by eucalypt forest.
Different N-fertilization sources affecting the native soil organic matter mineralization on Technosols under iron ore tailing
(Revista Brasileira de Ciência do Solo, 2020-10-07) Oliveira, Paula Afonso de; Assis, Igor Rodrigues de; Dias, Luiz Eduardo; Silva, Ivo Ribeiro da; Barbosa, Gustavo Magalhães Nunes; Teixeira, Rafael da Silva; Campos, Rafaella
Accidents related to the rupture of iron ore tailings dams have dramatically impacted on the Brazilian natural ecosystem. So, the development of strategies to recover soil organic matter levels and build-up Technosols are required. This study aimed to evaluate the effect of N-mineral and -organic fertilization and the rhizospheric effect on soil organic matter mineralization from Technosols built under iron ore tailings. The experiment was carried out in a greenhouse; we used a factorial scheme 2 × 2 × 3: without and with the plant Crotalaria juncea; without and with mineral fertilization; and three different organic fertilization (without organic fertilization, sewage sludge, and household waste composting), with four randomized blocks. The experimental units were PVC columns installed with a top layer of iron ore tailing from a dam, where gases were sampled to determine the CO 2 -C, CH 4 -C concentrations, and CO 2 -δ 13 C. The organic fertilization promoted a positive priming effect of 184 %. However, with mineral fertilization, no effect was observed in soil derived-CO 2 -C accumulated and priming effect. Similarly to non-planted soil, the planted soils with mineral and organic fertilization promoted a steady reduction in soil derived-CO 2 -C accumulated and rhizosphere priming effect. The soil with mineral fertilization improved in 5.52 and 0.45 g per column the shoot and root dry matter of Crotalaria when compared to the soil without mineral fertilization. In summary, the organic fertilization in Technosols built over iron ore tailings dams during revegetation was not enough to ensure the plant development and preservation of soil organic matter. However, the combination of mineral and organic fertilization promoted negative rhizosphere priming effect and a significant increase in plant biomass.
Effect of mineral nitrogen on transfer of 13C-Carbon from Eucalyptus harvest residue components to soil organic matter fractions
(Revista Brasileira de Ciência do Solo, 2017-07-31) Demolinari, Michelle de Sales Moreira; Sousa, Rodrigo Nogueira de; Silva, Ivo Ribeiro da; Teixeira, Rafael da Silva; Neves, Júlio César Lima; Mendes, Gilberto de Oliveira
The amount of harvest residues retained in Eucalyptus plantations strongly influences soil organic matter (SOM), but the efficiency of conversion to SOM may vary according to the type of residue. This study evaluated the recovery of C from Eucalyptus residue components - leaves, bark, branches, roots, and a mix of all residues - in different SOM fractions with or without mineral-N supplementation (200 mg kg-1 of N). Variation in natural 13C abundance was used to trace the destination of residue-derived C in the soil. The C content of the light fraction (LF) and heavy fraction (HF) of SOM increased over a 240-days decomposition period in response to incorporation of Eucalyptus residues in the soil. Bark and leaf residues showed the best results. Bark residues increased the C content of the HF by 45 % over the initial condition. Leaf residues made the largest contribution to LF-C, increasing it by 8.6 times. Leaf residues also led to the highest N contents in the LF and HF, whereas branches, roots, and the mixture of residues caused significant net transfers of N from the HF. Mineral-N supplementation had no effect on stabilization of organic C in the HF of SOM, in which the C could be maintained for longer periods due to physical/colloidal protection against microbial decomposition. These results highlight the importance of keeping Eucalyptus harvest residues in the planted area, especially the bark, which is the most abundant harvest residue component under field conditions, for maintenance of SOM.
Soil organic matter fractions under eucalypt plantation in reform management
(Floresta e Ambiente, 2019) Soares, Emanuelle Merces Barros; Teixeira, Rafael da Silva; Sousa, Rodrigo Nogueira de; Vasconcelos, Aline de Almeida; Silva, Ivo Ribeiro da
Harvesting and reform in eucalyptus can lead to changes in soil organic matter (SOM). The objective of this work was to evaluate the changes in total organic C (TOC) and N (NT), C and N in humic acid (HA), fulvic acid (FH), light organic matter (LOM) and microbial biomass (MB), in Ultisol of eucalypt stands over one, two and four years of renovated areas in Rio Grande do Sul state. After the first year of eucalyptus reform, there were 78% of increases in TOC (0.0-1.0-m soil layer). After two years, there was an increase in TN and an average reduction of 52% in LOM-C (0.0-0.1-m soil layer). FA-C, HA-C, and HU-C presented mean reductions of 43 Mg ha–1 (0.0-1.0-m soil layer) after four years of reform. The litter contribution of previous crop and the crop residues from the harvest resulted in increments of the SOM fractions. However, there is a negative effect in later years.