Plant Nitrogen status driving soil organic matter mineralization in the rhizosphere

• Ano de defesa: 2016
• Autor(a) principal: Colocho Hurtarte, Luis Carlos
• Tipo de documento: Dissertação
• Tipo de acesso: Acesso aberto
• Idioma: eng
• Instituição de defesa: Universidade Federal de Viçosa
• Palavras-chave em Português: Plantas e solo; Solos florestais; Solos - Teor de compostos orgânicos; Solos - Humus; Eucalyptus ssp.; Plantas - Metabolismo; Ciência do Solo
• Link de acesso: http://www.locus.ufv.br/handle/123456789/10440

The factors that regulate the dynamics of soil Carbon (C) and Nitrogen (N) in the rhizosphere are still poorl y understood. The soil C mineralization in the rhizosphere ca n be heavil y influenced by plant’s nutritional status, atmospheric CO2 concentration and temperature, among others. In this study, we assess the influence of Eucalyptus spp. N status on the C and N dynamics in the rhizosphere. We performed an experiment us ing two compartment rhizobox. In the upper compartment, plants were cultivated in washed sand and supplied with a solution containing all nutrients or all nutrients but N. The lower compartment limited the contact of the roots with the soil using a 5 μm mesh nylon membrane. We observed a higher root-shoot ratio for the N deficient plants and an increase in its soil CO2 concentration. The roots of the –N planted treatment had higher concentrations of citrate and tallose and lower concentration of sucrose and aminoacids, when compared to the +N planted treatment. The C and N anal ysis of the mineral associated organic matter fraction, together with the thermochemol ysis data showed an increase in C mineralization in both planted treatments and changes in N dynamics. As the roots had no physical contact with the soil due to the nylon membrane, the changes in the soil must have been consequence of root exudation. The contrasting sugar and aminoacid root content, together with the citrate concentration in soil solut ion extract and the C mineralization data, indicate that exudate composition changed due to the plants N status. The data indicates that the plants in the –N treatment exudated more organic acids than the plants of the +N treatment. Still the exudate comp osition of the plants with the +N treatment may had a higher energetic content and thus affected differentl y the soil microbial communities. The δ13C data indicate that the N deficient plants affected a higher volume of soil than the plants of the +N treatment. All this together shows different priming mechanisms were dominant due to the plants N status. As the plants were N deficient, the mineralization of soil C was driven by the “N-mining” mechanism while in the soil of the +N planted treatment the dominant mechanism was “microbial stoichiometry”. This work demonstrates, to our knowledge, by the first time using the same plants, different priming mechanisms due to the plants N status. Thus highlighting, the importance of plants nutrient management in the rhizosphere C dynamics.