Interactions between repeated fire, nutrients, and insect herbivores affect the recovery of diversity in the southern Amazon

Abstract

Surface fires burn extensive areas of tropical forests each year, altering resource availability, biotic interactions, and, ultimately, plant diversity. In transitional forest between the Brazilian cerrado (savanna) and high stature Amazon forest, we took advantage of a long-term fire experiment to establish a factorial study of the interactions between fire, nutrient availability, and herbivory on early plant regeneration. Overall, five annual burns reduced the number and diversity of regenerating stems. Community composition changed substantially after repeated fires, and species common in the cerrado became more abundant. The number of recruits and their diversity were reduced in the burned area, but burned plots closed to herbivores with nitrogen additions had a 14 % increase in recruitment. Diversity of recruits also increased up to 50 % in burned plots when nitrogen was added. Phosphorus additions were related to an increase in species evenness in burned plots open to herbivores. Herbivory reduced seedling survival overall and increased diversity in burned plots when nutrients were added. This last result supports our hypothesis that positive relationships between herbivore presence and diversity would be strongest in treatments that favor herbivory—in this case herbivory was higher in burned plots which were initially lower in diversity. Regenerating seedlings in less diverse plots were likely more apparent to herbivores, enabling increased herbivory and a stronger signal of negative density dependence

Early recruitment responses to interactions between frequent fires, nutrients, and herbivory in the southern Amazon

“…We assessed the impact of these variables on woody species' regeneration and survival, diversity, and community composition. The results reported here build on long-term research in the area, testing the hypothesis that repeated fires may push forests to a tipping point beyond which they are converted to savanna-like ecosystems (Balch et al , 2011Brando et al 2012;Massad et al 2013). This work extends the findings of Massad et al (2013) which reported on regeneration during the first 6 months of seedling establishment after repeated fire.…”

“…As communities are redesigned by climate and land use, species interactions will both respond to (Stireman et al 2005;Menendez et al 2008;Tylianakis et al 2008;de Sassi et al 2012) and interact with abiotic factors to influence community composition and diversity ). More integrative studies are therefore needed to accurately understand ecosystem responses to global change as abiotic and biotic drivers will not operate in isolation.…”

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.…”

Influência da química do detrito foliar e da água sobre a comunidade de hifomicetos aquáticos

“…Queimadas recorrentes e severas não apenas alteram a estrutura e o microclima da floresta de modo a facilitar a invasão e o estabelecimento de gramíneas, mas também reduzem a competitividade de espécies lenhosas nativas; o fogo (i) mata as sementes das árvores por ação direta por meio do aquecimento , (ii) aumenta a predação de sementes de espécies de árvores nativas , (iii) reduz a germinabilidade das sementes Cochrane & Laurance, 2002;Massad et al, 2012) e (iv) e diminui a densidade e a diversidade de plântulas de espécies arbóreas Massad et al, 2012). Apesar dessas percepções, definir que nível de distúrbio é suficiente para causar mudança no estado desse sistema ainda é difícil.…”

“…Os solos são Latossolos Vermelho-Amarelo, distróficos, álicos, profundos e bem drenados RADAMBRASIL, 1981) Massad et al, 2012;Rocha et al, 2014 No sul da Bacia Amazônica, previsões sugerem recuo das florestas devido às mudanças climáticas Hutyra et al, 2005) e práticas de uso da terra Veldman et al, 2009), o que também pode facilitar a invasão por gramíneas e aumentar a frequência e a intensidade de incêndios florestais. Apesar de alguns modelos globais de dinâmica da vegetação indicarem retração das florestas Amazônicas no final do século Huntingford et al, 2004), ainda não há visão integrada de como esse processo ocorrerá.…”