Abstract
Aim of the study: To assess structure, recruitment and mortality rates of tree species over almost three decades, 14 years before and 15 years after a forest fire. Material and methods: All trees ≥ 5 cm in DBH were identified and measured in 12 permanent plots (50 m x 50 m), in 1983, 1987, 1989, 1995, 2008, and 2012 of a dense ombrophilous forest in Eastern Amazon, Brazil. The analyses were carried out including all sampled species and their ecological groups: shade-tolerant, light-demanding, and pioneer species. Treatments were compared through a Linear Mixed Effect Model. Main results: The 15-year post-fire period is not enough for the old-growth tropical forest to recover its pre-fire conditions of recruitment and mortality rates. The post-fire recruitment and mortality rates increased, mainly the recruitment of pioneer species (p-value < 0.05). Research highlights: In a period of 15 years after the occurrence of a surface fire, the old-growth tropical forest still has high recruitment rates of shade-tolerant and light-demanding species and high incidence of pioneer species, confirming the persistent fire effects on forest dynamics and species composition in this ecosystem. Keywords: pioneer tree species; species dynamics; forest resilience; Tapajós National Forest; Amazonian forests. Abbreviations used: DBH (diameter at 1.3 m from the ground); D (density); BA (basal area); EG (ecological group); ST (shade-tolerant); LD (light-demanding); Pi (pioneer); Ni (non-identified ecological group); MR (mortality rates); RR (recruitment rates); LMM (Linear Mixed Effect Model).
Highlights
High humidity and rainfall are climate features of the tropical forests that prevent natural fires
Mortality and recruitment rates were higher after fire in the burnt area (Fig. S2A [suppl.] and S2B [suppl.]; see Andrade et al 2019), and recruitment rates of pioneer species increased in the post-fire period, indicating a divergent pattern observed in the non-burnt area (F8.21 = 12.30; P < 0.01)
In 1995 in the non-burnt area, about 1.4% (0.45 m2 ha-1) of the basal area was composed by pioneer species, while in the burnt area this percentage was 5.72% (1.67 m2 ha-1)
Summary
High humidity and rainfall are climate features of the tropical forests that prevent natural fires. The increase of economic activities that require land use shifts from forests to crops and pastures have resulted in greater vulnerability of natural ecosystems to fires (Fernandes et al, 2011). In the Amazon, anthropogenic fires have become increasingly recurrent, which represents a potential threat to the biome’s rich biodiversity (Barlow et al, 2016). In this century, the Amazon will probably face increases in average temperatures, as well as more frequent and spread drought events (Betts et al, 2016). The knowledge of forest dynamics, Dárlison Fernandes-Carvalho-de-Andrade, Ademir Roberto Ruschel, Gustavo Schwartz et al
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