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<p>Vegetation of Amazonian savannas is relatively understudied in comparison with other tropical savannas. Here we studied how the combination of fire regime, recorded 24 years before the start of the study, and the physicochemical properties of the soil, were associated with tree structure, species richness, and species composition using samples collected in 29 plots spread across a threatened Amazonian savanna which is part of a Long-term Ecological Research Program. We hypothesized that fire would simplify the physical structure, the species richness, and alter the composition of tree savanna species, but that this will depend on the physical structure and chemical composition of the soil, particularly the percentage of clay. A total of 3,520 individual trees from 28 species in 20 botanical families were recorded. We did not find a significant interaction between fire regime and soil properties for any relationship tested, suggesting that they act independently. Tree density was lower in areas with high fire frequency, while the physicochemical components of the soil (especially clay, N, P, K, Al, S and organic matter content) were positively associated with density, biomass and species richness. Both fire and soil physicochemical properties were associated with species composition. These results suggest that soil characteristics are the primary determinants of the structure and composition of plant species in this Amazonian savanna, with fire acting as a secondary factor. Experimental studies are necessary to disentangle the role of fire from soil effects in this system, while urgent actions must be taken to protect it.</p>

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Community structure, biomass, and tree species composition across soil and fire gradients in a threatened Amazonian savanna

  • 期刊论文

  • 发表日期：

    2025年9月8日

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  • Vanessa Sousa Gomes,
  • Viviane Vasconcelos Corrêa Dourado,
  • José Júlio Toledo,
  • Albertina Pimentel Lima,
  • Rodrigo Ferreira Fadini

摘要

Vegetation of Amazonian savannas is relatively understudied in comparison with other tropical savannas. Here we studied how the combination of fire regime, recorded 24 years before the start of the study, and the physicochemical properties of the soil, were associated with tree structure, species richness, and species composition using samples collected in 29 plots spread across a threatened Amazonian savanna which is part of a Long-term Ecological Research Program. We hypothesized that fire would simplify the physical structure, the species richness, and alter the composition of tree savanna species, but that this will depend on the physical structure and chemical composition of the soil, particularly the percentage of clay. A total of 3,520 individual trees from 28 species in 20 botanical families were recorded. We did not find a significant interaction between fire regime and soil properties for any relationship tested, suggesting that they act independently. Tree density was lower in areas with high fire frequency, while the physicochemical components of the soil (especially clay, N, P, K, Al, S and organic matter content) were positively associated with density, biomass and species richness. Both fire and soil physicochemical properties were associated with species composition. These results suggest that soil characteristics are the primary determinants of the structure and composition of plant species in this Amazonian savanna, with fire acting as a secondary factor. Experimental studies are necessary to disentangle the role of fire from soil effects in this system, while urgent actions must be taken to protect it.