Impact of drainage and soil hydrology on sources and degradation of organic matter in tropical coastal podzols

Autor(es)

Lopes-Mazzetto, Josiane Millani ^[1] ; Schellekens, Judith ^[1] ; Vidal-Torrado, Pablo ^[1] ; Buurman, Peter ^[2]

Afiliação do(s) autor(es)

^[1] Univ Sao Paulo, ESALQ, Dept Ciencia Solo, Av Padua Dias 11, Piracicaba, SP - Brazil

^[2] Wageningen Univ, Water Syst & Global Change Grp, POB 47, NL-6700 AA Wageningen - Netherlands

• Tipo de documento: Artigo Científico
• Fonte: Geoderma; v. 330, p. 79-90, NOV 15 2018.
• Citações Web of Science: 2

Resumo

In podzols important environmental issues converge, including dissolved organic matter (DOM) transport, DOM-metal binding, and carbon storage in the subsoil. Therefore, it is important to understand the formation and degradation of podzols in relation to (changes in) environmental conditions. For this purpose a Holocene barrier island with coastal sand dunes (Ilha Comprida, SE Brazil) was chosen as study area. The island is build-up of five geomorphic units that have different age (from > 5000 to 325 y BP), vegetation (restinga ecosystems), soil hydrology (flat units or units with ridges and swales) and drainage (poorly drained, well-drained, and improved drainage). Representative profiles were studied for each geomorphic unit, resulting in 100 samples from A, E, B, and C horizons, from which soil organic matter (SOM) was isolated by alkaline extraction. To better understand carbon sources and dynamics, we additionally sampled litter from different vegetation types and DOM from various sources. The molecular composition of SOM, DOM and litter was analyzed with pyrolysis gas chromatography mass spectrometry (pyrolysis-GC/MS). Comparing the pyrolysates of all samples (DOM, SOM and litter) factor analysis demonstrated that the major difference in molecular composition (factor 1) was related to the contribution from DOM (phenol, acetic acid, benzofurans, pyridine, benzene and naphthalene) or in-situ root material (straight chain aliphatics and methoxyphenols from the biomacromolecules suberan and lignin, respectively). The contribution from DOM or roots was characteristic for a profile i.e. without much change with depth. Factor 2 reflected decomposition processes, and showed that the predominantly DOM-derived B horizons were relatively enriched in aromatics compared to DOM, indicating selective decay and/or selective precipitation. In geomorphic units with swales and ridges that received DOM via groundwater flow from the catchment area, the B horizon was predominantly DOM-derived; these profiles showed large differences in the contribution from black carbon (BC; (poly)aromatics), with the younger profiles showing a larger contribution from BC in precipitated DOM. B horizons with a relatively large contribution from in-situ root materials were found in well-drained soils and in some of the poorly drained soils without lateral groundwater flow from the catchment area, i.e., the flat geomorphic unit without ridges and swales. Microbial material (N-containing compounds and sugars) was associated with relatively recent SOM and with well-drained conditions at present, i.e., well-drained profiles, and profiles with improved drainage. (AU)

• Processo FAPESP: 12/22405-0 - Podzolização em solos sob vegetação de restinga: relações entre a variação de drenagem, acumulação e composição da matéria orgânica em Espodossolos na Ilha Comprida - SP
• Beneficiário: Josiane Millani Lopes
• Modalidade de apoio: Bolsas no Exterior - Estágio de Pesquisa - Doutorado
• Processo FAPESP: 13/03953-9 - Dinâmica da matéria orgânica em organossolos de turfeiras tropicais (Diamantina-MG, Brasil) - desenvolvimento de proxies moleculares para a reconstrução de mudanças paleoambientais
• Beneficiário: Judith Schellekens
• Modalidade de apoio: Bolsas no Brasil - Pós-Doutorado
• Processo FAPESP: 14/23969-0 - Dinâmica da matéria orgânica do solo e sua relação com o ambiente e com processos pedogenéticos: química molecular (pirólise-CG/EM) de solos tropicais
• Beneficiário: Pablo Vidal Torrado
• Modalidade de apoio: Auxílio à Pesquisa - Regular