Reduced predation by arthropods and higher herbivory in burned Amazonian forests

Abstract

Biodiversity losses have increased in tropical forests due to fire-related disturbances.As landscape fragmentation and climate change increase, fires will become more frequent and widespread across tropical rain forests worldwide, with important implications for forest dynamics by altering plant-animal interactions. Here we tested the hypothesis that recurrent fires in tropical rain forests change bottom-up and topdown forces controlling the abundance of insect herbivores, which in turn increases herbivory. To quantify herbivory, we collected 50 leaves per tree of five species in burned and unburned experimental plots (N = 75) in southeastern Amazonian forests.We measured leaf nitrogen content and leaf thickness of tree leaves as bottom-up factors that could explain differences in herbivory; we measured predation pressure on model caterpillars and estimated the abundance of predatory ants as top-down factors. We found higher herbivory in burned than in unburned forests, as well as lower predator attacks in caterpillar models and lower abundance of predatory ants.Leaf nitrogen content did not vary across treatments. Birds attacked model caterpillars more frequently in burned than in unburned forests, and leaf thickness was higher in burned forests, but these factors together were not enough to offset the higher herbivory in burned plots. Fire degrades tropical forests not only by killing trees and altering their structure and community dynamics, but also by reducing predatory arthropods and disrupting predator-prey interactions, which triggers increased herbivory. These indirect impacts of recurrent fires probably contribute to further alter forest structure, functioning, and to decrease regeneration in Amazonian forests.

Site Quality for Araucaria angustifolia Plantations with Subtropical Cambisol Is Driven by Soil Organism Assemblage and the Litter and Soil Compartments

“…In L-SQ stands, we found a significant decrease in the abundance of predators from Araneidae, Acaridae, Carabidae, and Mantidae, which may be related to active biological control. These results agree with the studies carried out by Gomez et al [24] and Queiroz et al [68], who reported a low abundance of predators, especially Arachnids, in soils with a low content of soil organic matter and low litter deposition. In L-SQ, we found an ecological impact described as habitat simplification.…”

Site quality for Araucaria angustifolia plantations with subtropical Cambisol is driven by soil organism assemblage and the litter and soil compartments

“…In the low site quality stands, we found a signi cant decrease in the abundance of predators Araneidae, Acaridae, Carabidae, and Mantidae, which may be related to active biological control. These results agree with the studies done bySouza et al (2023b), andQueiroz et al (2022), who reported low abundance of predators, especially Arachnids in soils with low content of soil organic matter, and low litter deposition.…”

Ecosystem functions of ants and dung beetles in agriculture‐dominated Amazonian riparian forests

“…We identified ants to species level at the Laboratório de Ecologia de Comunidades e Ecossistemas Tropicais (EcoTrop) at Universidade Federal de Viçosa, MG, Brazil. We classified sampled ants into predatory and non-predatory, according to Baccaro et al (2015) and Queiroz et al (2022) (Table S1). Dung beetles were identified by a specialist (Dr. Fernando Vaz-de-Melo) at the Laboratório de Scarabaeoidologia, at Universidade Federal do Mato Grosso, MT, Brazil.…”

“…They prey on several animal groups (Hölldobler & Wilson, 1990), shape other insect communities (Tuma et al, 2020) and contribute to increased plant diversity via top-down control (Leles et al, 2017). In burned forests, for example, higher tree herbivory is related to a decrease in the abundance of predatory ants (Queiroz et al, 2022). Predatory insects usually decline with habitat conversions to agricultural landscapes (Tscharntke et al, 2012), but it is still unknown whether top-down control performed by predatory ants decreases in forest fragments surrounded by croplands.…”