Herbivory in southeastern Brazilian mangroves: An analysis of 11 years of litterfall monitoring

Abstract

Severe defoliation of mangrove species is reported in several parts of the world. We analyzed the effect of a severe defoliation event resulting from the attack of a lepidopteran caterpillar (an insect outbreak) on the litterfall production. The attack occurred between 2009 and 2010 in a mangrove in southeastern Brazil. Leaf litter production by different mangrove species between 2008 and 2019, was considered in the analysis. The infestation directly affected the species Avicennia schaueriana Stapf & Leechm in all physiographic types assessed, with a decrease in leaf litter production between 43% and 86% since the monitoring began (2009) until the year when defoliation reached the maximum (2011). A decrease in the impact of defoliation was observed along the tidal flooding gradient, with more pronounced effects in forests located in the transition zone with the salt-flat, and progressive decrease towards fringe forests. In fringe and basin forests, leaf litter production by Laguncularia racemosa (L.) decreased between 52% and 67% between 2009 and 2011, respectively, and increased 30% in transition forests. Contrarily, the contribution of Rhizophora mangle (L.) increased 7% in basin, became noticeable in transition, and decreased by 25% in the fringe forests. The time required for A. schaueriana to recover the level of debris production was 8 years, and still reflect the effect of the severe, selective defoliation process on the dynamics and ecological succession of mangrove forests. A model that determines the stages of defoliation and their direct and indirect impacts on litter was developed.