Photodegradation influences litter decomposition rate in a humid tropical ecosystem, Brazil

Autor(es)

Marinho, Osmarina A. ^[1] ; Martinelli, Luiz A. ^[1] ; Duarte-Neto, Paulo J. ^[2] ; Mazzi, Edmar A. ^[1] ; King, Jennifer Y. ^[3]

Afiliação do(s) autor(es)

^[1] Univ Sao Paulo, Ctr Nucl Energy Agr, BR-13400970 Piracicaba, SP - Brazil

^[2] Univ Fed Rural Pernambuco, Dept Stat & Informat, BR-52171900 Recife, PE - Brazil

^[3] Univ Calif Santa Barbara, Dept Geog, Santa Barbara, CA 93106 - USA

• Tipo de documento: Artigo Científico
• Fonte: Science of The Total Environment; v. 715, MAY 1 2020.
• Citações Web of Science: 0

Resumo

Solar radiation in general and UV radiation in particular have been recognized to stimulate plant litter decomposition through photochemical mineralization of organic molecules such as lignin and through facilitation of microbial decomposition in dryland ecosystems. However, little is known about how photodegradation may influence decomposition in other ecosystems not subject to moisture limitations and under what conditions photodegradation may be favored. Decomposition in humid tropical ecosystems is a complex process, and it can be influenced by a number of environmental factors that are distinct from arid and semi-arid ecosystems. To assess the mechanisms underlying photodegradation by ultraviolet B (UV-B) radiation in a humid tropical ecosystem, we designed a 300-day field experiment in a tropical site in Brazil with high levels of annual precipitation, compared to arid ecosystems, and exposed litter to three levels of radiation (full sun, UV-B removed, and shade) combined with a biocide treatment. Results show that after nearly one year of exposure, the microbial biomass was not affected by UV-B incidence, and this effect has not yet been fully understood for tropical ecosystems. Modeled using an exponential deceleration equation, the removal of UV-B radiation decelerated the plant litter decomposition rate for the control conditions by 21% compared to litter exposed to full sun. Interestingly, shaded litter exhibited similar mass loss compared to litter exposed to full sun. Furthermore, differences in the decay constant among radiation treatments due to the UV-B effect were independent of lignin loss. Overall, our study suggests that UV-B radiation contributed to plant litter decomposition through carbon losses but had no discernible effect on nitrogen, lignin, or cellulose loss specifically. Importantly, our results demonstrate that photodegradation occurs under humid tropical conditions, and further studies are necessary to examine the mechanisms of carbon loss. (C) 2020 Published by Elsevier B.V. (AU)

• Processo FAPESP: 16/09698-9 - Efeitos da radiação UV-B na decomposição da serapilheira em um ecossistema tropical - Determinação da constante K de decomposição e qualidade da serapilheira.
• Beneficiário: Osmarina Alves Marinho
• Modalidade de apoio: Bolsas no Exterior - Estágio de Pesquisa - Mestrado
• Processo FAPESP: 15/00971-1 - Decomposição da serapilheira sob efeito da fotodegradação em um ecossistema de floresta ombrófila densa montana no Litoral Norte do Estado de São Paulo
• Beneficiário: Osmarina Alves Marinho
• Modalidade de apoio: Bolsas no Brasil - Mestrado