Illegal selective logging and forest fires occur on a large scale in the northern Brazilian Amazon, contributing to an increase in tree mortality and a reduction in forest carbon stock. A total of 120 plots of 0.25 ha (30 ha) were installed in transitional ecosystems or ecotones (LOt) between the forested shade-loving campinarana (Ld) and dense-canopy rainforest, submontane (Ds), in the National Forest (Flona) of Anauá, southern Roraima. Measuring the diameters at breast height (DBH ≥ 10 cm) and the heights of 171 dead trees (fallen naturally, illegally exploited, and affected by forest fires), enabled the estimation of carbon content from the application of a biomass equation developed at Manaus, and the calculation of a correction factor, using the average height of the largest trees. From 2015–2017, we mapped the real extent of illegal selective logging and forest fires across the region with CLASlite and INPE/Queimadas. From measurements of 14,730 live and dead trees across 30 hectares (491 ± 15 trees·ha⁻¹), the illegal selective logging and associated forest fires, and aggravation by severe El Niño droughts resulted in an 8.2% mortality of trees (40 ± 9 dead trees·ha⁻¹) and a 3.5% reduction in forest carbon stock (6 ± 3 Mg·ha⁻¹) in the short-term. The surface area or influence of forest fires of very high density were estimated in the south-central region of Roraima (8374 km²) and the eastern region of the Flona Anauá (37 km²). Illegal selective logging and forest fires in forest areas totaled 357 km² in the mosaic area, and 6 km² within Flona Anaua. Illegal selective logging and forest fires in the years of severe El Niño droughts threatened the maintenance of environmental services provided by Amazonian forests.

Long-term studies of the dynamics of managed forests in tropical regions are lacking. This study aimed to evaluate the dynamics of a tropical forest, over a 25-year period, that was experimentally logged in 1987 and 1988 and submitted to three different cutting intensities. All trees with diameter at breast height (DBH) ≥ 10 cm have been measured annually since 1990. The three logging intensities that were applied were: light (T1)-trees harvested with DBH ≥ 55 cm; medium (T2)-DBH ≥ 50 cm; and heavy (T3)-DBH ≥ 40 cm. Control plots (T0) were also monitored. The highest mean annual mortality rates (1.82% ± 0.38), recruitment rates (2.93% ± 0.77) and diameter increments (0.30 ± 0.02 cm) occurred in the T3 treatment. Shifts in dynamics of the forest were mainly caused by a striking increase in a fast-growing pioneer species and their high mortality rates. The loss in stocking caused by mortality was greater than to that of replacement by recruitment. The results demonstrated that selective logging altered the natural dynamics of the forest through increased: mortality rates, recruitment and growth rates of the residual trees.

Every year, logging in the world’s largest tropical forest, located within the Amazon biome, continues unabated. Although it is a preferred alternative to deforestation, the residual stand and site are impacted by logging. The objective of this review was to determine and assess the current state of research throughout Amazonia on the subject of logging impacts. To achieve this goal, a systematic approach was utilized to gather, assess and categorize research articles conducted in the Amazon biome over the last decade. Eligibility for inclusion of articles required demonstration of a direct impact from logging operations. A total of 121 articles were determined to meet the eligibility requirements and were included in this review. Articles were subdivided into three environmental categories: forest (n = 85), wildlife (n = 24) and streams (n = 12). The results of this review demonstrated that impacts from logging activities to the forest site were a direct result of the logging cycle (e.g., how often logging occurs) or logging intensity (e.g., how many trees are felled). The impacts to wildlife varied dependent on species, whereas impacts to streams were affected more by the logging system. Overall, research suggested that to attain sustainability and diminish the impacts from logging, a lower logging intensity of 10–15 m³ ha⁻¹ and a longer logging cycle of 40–60 years would be essential for the long-term viability of forest management in Amazonia.

The Eschweilera genus has great ecological and economic importance due to its wide abundance in the Amazon basin. One potential use for the Eschweilera genus is in forest management, where just a few trees are removed per hectare. In order to improve the forest management in the Amazon, this study assessed two critical issues: volume equations fitted for a single genus and the development of a non-destructive method using climbing techniques. The equipment used to measure the sample trees included: climbing rope, ascenders, descenders, and carabiners. To carry out the objectives of this study, 64 trees with diameter at breast height (DBH) ≥ 10 cm were selected and measured in ZF-2 Tropical Forestry Station near the city of Manaus, Brazil. Four single input models with DBH and four dual input models with DBH and merchantable height (H) were tested. The Husch model (V = a × DBH^b) presented the best performance (R² = 0.97). This model does not require the merchantable height, which is an important advantage, because of the difficulty in measuring this variable in tropical forests. When the merchantable height data are collected using accurate methods, the Schumacher and Hall model (V = a × DBH^b × H^c) is the most appropriated. Tree climbing techniques with the use of ropes, as a non-destructive method, is a good alternative to measure the merchantable height, the diameter along the stem, and also estimate the tree volume (m³) of the Eschweilera genus in the Amazon basin.

O artigo “A floresta amazônica e a água da chuva” apresenta que a precipitação média anual é a principal variável meteorológica para o setor florestal da Amazônia. A temperatura média anual varia pouco dentro da Amazônia Legal - apenas 8%. A precipitação média anual apresenta uma variação maior, quase 100%. O crescimento e incremento das árvores amazônicas apresentam correlações significativas com a precipitação. A precipitação interanual apresenta sinais mais fortes que a intra-anual, para explicar essas correlações. Apenas o crescimento e incremento não são suficientes para determinar se a floresta está sequestrando ou emitindo carbono. As taxas de mortalidade e recrutamento desempenham papel importante para estimar esse balanço. Elas apresentam relações intrínsecas com a precipitação. A falta ou excesso de chuvas influencia, principalmente, nas taxas de mortalidade. Na escala regional, a falta de chuvas tem contribuído com o aumento da mortalidade das árvores amazônicas; na escala de comunidades, é o excesso de chuvas que mais contribui para o aumento da mortalidade. São apresentados os resultados das ocorrências de dois fenômenos meteorológicos no mesmo ano, que atingiu a região amazônica. Numa escala de comunidade utilizando três parcelas permanentes (1 ha), os resultados são analisados para dimensionar os efeitos dos dois fenômenos na floresta.Palavras-chave: Taxa de mortalidade; seca; downburst; dinâmica. AbstractThe Amazon Forest and the rain. The article "The Amazon Forest and the rain" shows that the average annual rainfall is the main weather variable for the forestry sector in the Amazon. The average annual temperature has little variation in the Amazon; only 8%. The average annual rainfall has a greater variation, almost 100%. The growth and increment of Amazonian trees show significant correlations with precipitation. The interannual precipitation presents stronger signals than the intra-annual one to explain these correlations. Only the growth and increment of trees are not enought to determine whether the forest is sequestering or emitting carbon. Mortality and recruitment rates play an important role to estimate this balance. These rates have intrinsic relationships with rainfall. The lack or excess of rain influence, mainly, mortality rates. On a regional scale, the lack of rain has contributed to the increased mortality of tropical rainforest trees; in the range of communities is the heavy rainfall that contributes to increased mortality. This article presents the results of two occurrences of weather phenomena in the same year, which reached the Amazon region. In community scale, using three permanent plots (1 ha), results are analyzed to gauge the effects of both phenomena in the forest.Keywords: Mortality rate; drought; downburst; dynamics.