Influências de Atta spp. (Hymenoptera: Formicidae) na recuperação da vegetação pós-fogo em floresta de transição amazônica

Abstract

ResumoEste estudo investigou o papel das saúvas na recuperação da vegetação pós-fogo. Foi hipotetizado que a perturbação do fogo aumenta a abundância de ninhos de saúva (1) e as atividades de remoção de sementes (2) e desfolha (3), especialmente no ambiente de borda. os ninhos de saúva foram inventariados e mapeados e após 17 meses, checados para o registro de sua atividade e de novas colônias emergindo na área. realizou-se experimentos comparativos de remoção de sementes e desfolha de plântulas em duas parcelas de 50 ha, uma submetida a fogo anual (tratamento) e outra sem fogo (controle). a abundância de ninhos de saúva foi maior na parcela tratamento que na parcela controle, especialmente na borda da floresta. as espécies encontradas foram: Atta cephalotes, A. laevigata e A. sexdens , sendo esta última a espécie mais abundante e que mostrou aumento em número de colônias ativas após 17 meses. o aumento na abundância de ninhos na parcela tratamento foi acompanhado por um aumento na atividade dessas formigas. Enquanto mais de duas folhas foram arrancadas por plântula nessa parcela, menos de uma foi registrada na parcela controle. também a abundância média de galhos desfolhados e de sementes removidas por saúvas foi maior na parcela tratamento que na parcela controle. as saúvas tanto podem diminuir ou retardar o processo de regeneração florestal pós-fogo, quanto acelerá-lo, devido à elevada predação seletiva que favorece as espécies menos palatáveis. Desta forma, suas atividades podem modificador apenas a composição da vegetação recuperando-se do fogo. PalavRas-Chave: saúvas, herbivoria, remoção de sementes, regeneração florestal.Influences of leafcutter ant Atta spp. (Hymenoptera: Formicidae) on vegetation recovery after fire in Amazonian transitional forest abstRaCt in this study we investigated the role of leaf-cutting ants in the post-fire vegetation recovery. We hypothesized that a forest plot submitted to annual fire presents: (1) higher abundance of leaf-cutting ant nests; (2) higher removal of seeds; and (3) higher herbivory rates of leaf-cutting ants, when compared to the forest plots without fire (control). The leaf-cutting ant nests were sampled, mapped, and checked up (after 17 months) to register their activity and new colonies emerging from the plot. We made comparative experiments of seeds removal and seedlings herbivory in two 50 ha plots, one submitted to annual fire and another without fire. The abundance of leaf-cutting nests was higher in the plot submitted to fire than in the control plot. The species found were: Atta cephalotes, A. laevigata, and A. sexdens, being the latter the most abundant and the one that showed an increase of active colonies after 17 months. The plot submitted to fire showed a higher abundance of seeds removed by leafcutting ants than the control. While more than two leaves were ripped per seedling in the plot under fire, less than one was registered in the control plot. it was also observed that the average abundance of seedlings attacked by leaf-cutting ant in the fire...

Testing the Amazon savannization hypothesis: fire effects on invasion of a neotropical forest by native cerrado and exotic pasture grasses

“…Repeated and severe fires not only alter forest structure and microclimate in ways that facilitate grass invasion and establishment, but also reduce the competitiveness of the native woody vegetation; fires (i) kill seed trees [19], (ii) increase seed predation of native tree species [45], (iii) lower seed germination [10,44,46] and (iv) reduce tree seedling density and diversity [46,47]. Despite these insights, the question of how much disturbance is too much to cause a change in the state of this system is still hard to answer.…”

Effect of Fire on Ant Assemblages in Brazilian Cerrado in Areas containing Vereda Wetlands

“…Changes caused by fire on ant communities may result in substantial indirect impacts on the vegetation at a mid-term scale (Carvalho et al, 2012;Beaumont et al, 2013). Research on ant community responses to the impact of natural or prescription fire suggests that ants are resilient and resistant to vegetation burning (Knoechelmann & Morais, 2008;Andersen et al, 2012;Frizzo et al, 2012;Alves-Silva & Del-Claro, 2013).…”

“…Nevertheless, ants with deeper nests are more likely to survive, as natural fires do not cause large elevations in the underground temperatures (Coutinho, 1978). This is the case with the attines (Atta and Acromyrmex), which build deep nests and, due to their architecture, are able to stabilize fluctuations in temperature and humidity (Farji-Brener, 2000;Carvalho et al, 2012).…”

Edge effect on post-dispersal artificial seed predation in the southeastern Amazonia, Brazil

“…This might happen through several factors, for example: the number of leaf-cutting ants' (Atta spp.) nests increases in disturbed areas (Wirth et al, 2007;Meyer et al, 2009) including fire disturbance (Carvalho et al, 2012). These ants species affects plant recruitment increasing (by seed dispersion) or decreasing (by seed predation and herbivory) altering the forest structure.…”