In Brazil’s state of Acre, in southwestern Amazonia, wildfires mediated by extreme droughts in 2005 and 2010 affected more than 500,000 ha of forest, causing changes in their structure, species diversity, and aboveground biomass (AGB), and the expansion of bamboo. Our objective was to analyze these changes in an open bamboo forest in Acre after forest fires occurred either in one of the extreme drought years (2005 or 2010) or in both years (2005 + 2010). We sampled 9.75 ha (in 2016 and 2017), distributed in 18 0.5 ha (100 m × 50 m) plots and three 0.25-ha (50 m × 50 m) plots. We identified a strong fire effect on the number of tree individuals per hectare, which declined by 50% if the forest was burned in only one year (2005 or 2010) and by 74% if burned in both years. This was inversely related to the expansion of bamboo stems, which increased in number by 7 to 9 times. Changes in forest structure and species composition after the fire were characterized by a high importance value for pioneer tree species; reductions in the number of trees with logging potential, in the basal area of trees, and in the number of lianas; and an increase in the density of bamboo stems. AGB in the burned forests was 51–73% that of the unburned forest. With the expansion of bamboo, its contribution to AGB increased from 1% in the unburned forest to 27% in the twice-burned forest. These forms of degradation represent serious threats to Amazon forests.

在巴西亚马孙州西南部的英亩州，2005年和2010年的极端干旱介导的野火影响了超过500,000公顷的森林，导致其结构，物种多样性和地上生物量（AGB）发生变化，竹子膨胀。我们的目标是分析在极端干旱年份（2005年或2010年）之一或两个年份（2005年+ 2010年）发生森林火灾后，在英亩的一片开放竹林中的这些变化。我们采样了9.75公顷（2016年和2017年），分布在18个0.5公顷（100 m×50 m）的样地和三个0.25公顷（50 m×50 m）的样地中。我们确定了对每公顷树木个体数量的强烈燃烧效应，如果仅在一年（2005年或2010年）内燃烧森林，则减少50％，而在两年内燃烧则减少74％。这与竹茎的膨胀成反比，数量增加了7到9倍。火灾后森林结构和物种组成的变化以先锋树种的重要价值为特征。减少具有伐木潜力的树木数量，树木的基础区域以及藤本植物的数量；并增加了竹茎的密度。烧过的森林中的AGB为未烧过的森林的51–73％。随着竹子的扩大，其对AGB的贡献从未燃烧森林的1％增加到两次燃烧森林的27％。这些退化形式对亚马逊森林构成了严重威胁。在树木的基础区域和藤本植物的数量中；并增加了竹茎的密度。烧过的森林中的AGB为未烧过的森林的51–73％。随着竹子的扩大，其对AGB的贡献从未燃烧森林的1％增加到两次燃烧森林的27％。这些退化形式对亚马逊森林构成了严重威胁。在树木的基础区域和藤本植物的数量中；并增加了竹茎的密度。烧过的森林中的AGB为未烧过的森林的51–73％。随着竹子的扩大，其对AGB的贡献从未燃烧森林的1％增加到两次燃烧森林的27％。这些退化形式对亚马逊森林构成了严重威胁。