Biogeochemistry of dissolved organic matter and inorganic solutes in soil profiles of tropical pasturelands

Autor(es)

dos Santos, Joao Vitor ; Goranov, Aleksandar I. ; Bento, Lucas R. ; Oliveira, Patricia P. A. ; Pezzopane, Jose R. M. ; Bernardi, Alberto C. C. ; de Sa, Ivero P. ; Nogueira, Ana Rita A. ; Martin-Neto, Ladislau ; Hatcher, Patrick G.

• Tipo de documento: Artigo Científico
• Fonte: SOIL & TILLAGE RESEARCH; v. 240, p. 15-pg., 2024-03-23.

Resumo

Tropical soils play a critical role in the global biogeochemical cycles and are essential for maintaining the Earth's carbon balance. Understanding the dynamics of dissolved organic matter (DOM) is paramount due to its implications for ecosystem functioning and nutrient cycling. This study comprehensively evaluated the origin, distribution, and composition of DOM and inorganic solutes in Brazilian tropical agricultural soils. Multiple analytical techniques were utilized to assess DOM from soil profiles (0-100 cm depth) across a spectrum of land uses, including a native Atlantic Forest, a degraded pasture, as well as intensive grazing, extensive grazing, and silvopastoral systems. Inorganic elements were quantified to assess the coupling between the organic and inorganic biogeochemical cycles. The dominance of C4 carbon in topsoil layers suggested substantial contributions of organic matter from grasses to the soil organic matter pool. However, with increased depth, C3 carbon inputs became more prominent, indicating the influence of forest vegetation that existed prior to the implementation of agricultural managements. DOM concentrations decreased with soil depth due to reduced carbon inputs, sorption to minerals, or oxidation. DOM composition did not show significant changes among different land use and managements. Lignin was identified as the primary contributor to oxidized DOM with increasing soil depth. The composition of DOM exhibited a shift from more aromatic and higher molecular weight compounds in topsoil layers to smaller, more aliphatic compounds in subsoil layers. Our key findings revealed that aliphatic compounds, particularly fatty acids, tend to accumulate in deeper soil layers. This phenomenon was consistent in pastures dominated by grasses but not in soils near treed vegetation. Overseeding (from C3 plants) did not significantly impact DOM compositions, emphasizing the persistence of C4 plants in these systems. The presence of inorganic elements in soil water extracts showed minimal impact on DOM dynamics, suggesting decoupled organic and inorganic biogeochemical cycles in tropical pasturelands. (AU)

• Processo FAPESP: 23/02444-5 - Entendendo sistemas intensificados e integrados de produção: do mundo quântico à agricultura de baixa emissão de carbono
• Beneficiário: Ladislau Martin Neto
• Modalidade de apoio: Auxílio à Pesquisa - Programa de Pesquisa sobre Mudanças Climáticas Globais - Temático
• Processo FAPESP: 21/08362-5 - Origem, composição molecular e destino da matéria orgânica dissolvida em sistemas de pastagem intensiva e integração pecuária-floresta
• Beneficiário: João Vitor dos Santos
• Modalidade de apoio: Bolsas no Exterior - Estágio de Pesquisa - Mestrado
• Processo FAPESP: 20/04938-7 - Quantificação e caracterização espectroscópica da matéria orgânica dissolvida de solos sob pastagens e sistemas integrados de produção
• Beneficiário: João Vitor dos Santos
• Modalidade de apoio: Bolsas no Brasil - Mestrado
• Processo FAPESP: 17/20084-5 - Práticas estratégicas para mitigação das emissões de gases de efeito estufa em sistemas de pastagem do Sudeste brasileiro
• Beneficiário: Paulo Henrique Mazza Rodrigues
• Modalidade de apoio: Auxílio à Pesquisa - Programa de Pesquisa sobre Mudanças Climáticas Globais - Temático
• Processo FAPESP: 19/18267-0 - Mecanismos de estabilização da matéria orgânica em solos tropicais em áreas com sequestro de carbono: avaliação por métodos físico-químicos e modelagem de carbono
• Beneficiário: Lucas Raimundo Bento
• Modalidade de apoio: Bolsas no Brasil - Doutorado