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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.
