Lightning is a major cause of large tree mortality in a lowland neotropical forest.

The mortality rates of large trees are critical to determining carbon stocks in tropical forests, but the mechanisms of tropical tree mortality remain poorly understood. Lightning strikes thousands of tropical trees every day, but is commonly assumed to be a minor agent of tree mortality in most tropical forests. We use the first systematic quantification of lightning-caused mortality to show that lightning is a major cause of death for the largest trees in an old-growth lowland forest in Panama. A novel lightning strike location system together with field surveys of strike sites revealed that, on average, each strike directly kills 3.5 trees (> 10 cm diameter) and damages 11.4 more. Given lightning frequency data from the Earth Networks Total Lightning Network and historical total tree mortality rates for this site, we conclude that lightning accounts for 40.5% of the mortality of large trees (> 60 cm diameter) in the short term and probably contributes to an additional 9.0% of large tree deaths over the long term. Any changes in cloud-to-ground lightning frequency due to climatic change will alter tree mortality rates; projected 25-50% increases in lightning frequency would increase large tree mortality rates in this forest by 9-18%. The results of this study indicate that lightning plays a critical and previously underestimated role in tropical forest dynamics and carbon cycling.

El Niño drought increased canopy turnover in Amazon forests.

Amazon droughts, including the 2015-2016 El Niño, may reduce forest net primary productivity and increase canopy tree mortality, thereby altering both the short- and the long-term net forest carbon balance. Given the broad extent of drought impacts, inventory plots or eddy flux towers may not capture regional variability in forest response to drought. We used multi-temporal airborne Lidar data and field measurements of coarse woody debris to estimate patterns of canopy turnover and associated carbon losses in intact and fragmented forests in the central Brazilian Amazon between 2013-2014 and 2014-2016. Average annualized canopy turnover rates increased by 65% during the drought period in both intact and fragmented forests. The average size and height of turnover events was similar for both time intervals, in contrast to expectations that the 2015-2016 El Niño drought would disproportionally affect large trees. Lidar-biomass relationships between canopy turnover and field measurements of coarse woody debris were modest (R2  ≈ 0.3), given similar coarse woody debris production and Lidar-derived changes in canopy volume from single tree and multiple branch fall events. Our findings suggest that El Niño conditions accelerated canopy turnover in central Amazon forests, increasing coarse woody debris production by 62% to 1.22 Mg C ha-1  yr-1 in drought years .

Abiotic niche partitioning and negative density dependence drive tree seedling survival in a tropical forest.

In tropical tree communities, processes occurring during early life stages play a critical role in shaping forest composition and diversity through differences in species' performance. Predicting the future of tropical forests depends on a solid understanding of the drivers of seedling survival. At the same time, factors determining spatial and temporal patterns of seedling survival can play a large role in permitting species coexistence in diverse communities. Using long-term data on the survival of more than 45 000 seedlings of 238 species in a Neotropical forest, we assessed the relative importance of key abiotic and biotic neighbourhood variables thought to influence individual seedling survival and tested whether species vary significantly in their responses to these variables, consistent with niche differences. At the community level, seedling survival was significantly correlated with plant size, topographic habitat, neighbourhood densities of conspecific seedlings, conspecific and heterospecific trees and annual variation in water availability, in descending order of effect size. Additionally, we found significant variation among species in their sensitivity to light and water availability, as well as in their survival within different topographic habitats, indicating the potential for niche differentiation among species that could allow for species coexistence.

Permeability - impermeability: canopy trees as biodiversity filters

Each tropical and subtropical forest canopy species may create specific microsite conditions below its crown, which works as a filter for those species that attempt to regenerate below it. In function of the permeability or impermeability level, each canopy species could partially determine a plant community structure and composition beneath its crown projection. Therefore, present and future forest plant community biodiversity could be partially determined by the present structure of the canopy tree species community (filter effect). Some theoretical and practical aftermaths are suggested.

Cada espécie do dossel das florestas tropicais e subtropicais pode criar microsítios específicos sob sua copa, que funcionam como filtros para aquelas espécies que tentam regenerar sob elas. Em função da permeabilidade ou impermeabilidade, cada espécie do dossel poderia parcialmente determinar a composição e estrutura da comunidade de plantas sob a projeção da sua copa. Portanto a biodiversidade presente e futura da comunidade de plantas da floresta poderia ser parcialmente determinada pela estrutura atual da comunidade de árvores do dossel (efeito de filtro). Alguns desdobramentos teóricos e práticos deste novo enfoque são sugeridos.

Permeability - impermeability: canopy trees as biodiversity filters

Each tropical and subtropical forest canopy species may create specific microsite conditions below its crown, which works as a filter for those species that attempt to regenerate below it. In function of the permeability or impermeability level, each canopy species could partially determine a plant community structure and composition beneath its crown projection. Therefore, present and future forest plant community biodiversity could be partially determined by the present structure of the canopy tree species community (filter effect). Some theoretical and practical aftermaths are suggested.

Cada espécie do dossel das florestas tropicais e subtropicais pode criar microsítios específicos sob sua copa, que funcionam como filtros para aquelas espécies que tentam regenerar sob elas. Em função da permeabilidade ou impermeabilidade, cada espécie do dossel poderia parcialmente determinar a composição e estrutura da comunidade de plantas sob a projeção da sua copa. Portanto a biodiversidade presente e futura da comunidade de plantas da floresta poderia ser parcialmente determinada pela estrutura atual da comunidade de árvores do dossel (efeito de filtro). Alguns desdobramentos teóricos e práticos deste novo enfoque são sugeridos.

Ingresso e mortalidade em uma floresta em diferentes estágios sucessionais no município de Castanhal, Pará / Recruitment and mortality in a forest in different successional stages in Castanhal, Pará

O presente trabalho descreve o ingresso e a mortalidade em uma floresta em diferentes estágios sucessionais, no município de Castanhal, Pará. A área de estudo está localizada na Estação Experimental da Universidade Federal Rural da Amazônia. As parcelas foram implantadas em áreas de florestas sucessionais de diferentes idades (4, 8 e 12 anos). Nas florestas sucessionais de 4 e 8 anos foram utilizadas quatro parcelas de 10m x 10m e na floresta de 12 anos foram, 12 parcelas de 10m x 10m. Realizaram duas medições de todos os indivíduos com DAP>1cm, em intervalos de 12 meses, nas florestas sucessionais de 4 e 8 anos; e intervalo de 18 meses na floresta de 12 anos. Foram calculadas as taxas de ingresso e de mortalidade. Na floresta de 4 anos o ingresso foi maior que a mortalidade. Nas florestas sucessionais de 8 e 12 anos as densidades diminuíram, perdendo mais indivíduos por mortalidade do que ganhando por ingresso. Lacistema pubescens, Myrcia silvatica, Vismia guianensis, Rollinia exsucca e Miconia ciliata apresentaram muitos indivíduos mortos nas florestas estudadas.

The present work describe recruitment and mortality in a forest in different successional stages in Castanhal, Pará. The study area is located at the Experimental Research Station of the Universidade Federal Rural da Amazônia. Twelve 10m x 10m study plots were established in a 12-year-old secondary forest, and four 10m x 10m study plots were demarcated in a 4-year-old and an 8-year-old secondary forest. We measured diameter and height of all individuals with DBH>1cm at a 12-month interval in the 4 and 8-year-old stands, and an 18-month interval in the 12-year-old stand. Using this inventory data we calculated recruitment and mortality rates. In the 4-year-old forest, recruitment was greater than mortality, while in the 8 and 12-year-old forests experienced net mortality, as density declined over the measurement interval. Lacistema pubescens, Myrcia sylvatica, Vismia guianensis, Rollinia exsucca and Miconia ciliata displayed the greatest number of dead individuals in the studied successional forests.

Ingresso e mortalidade em uma floresta em diferentes estágios sucessionais no município de Castanhal, Pará

The present work describe recruitment and mortality in a forest in different successional stages in Castanhal, Pará. The study area is located at the Experimental Research Station of the Universidade Federal Rural da Amazônia. Twelve 10m x 10m study plots were established in a 12-year-old secondary forest, and four 10m x 10m study plots were demarcated in a 4-year-old and an 8-year-old secondary forest. We measured diameter and height of all individuals with DBH>1cm at a 12-month interval in the 4 and 8-year-old stands, and an 18-month interval in the 12-year-old stand. Using this inventory data we calculated recruitment and mortality rates. In the 4-year-old forest, recruitment was greater than mortality, while in the 8 and 12-year-old forests experienced net mortality, as density declined over the measurement interval. Lacistema pubescens, Myrcia sylvatica, Vismia guianensis, Rollinia exsucca and Miconia ciliata displayed the greatest number of dead individuals in the studied successional forests.

O presente trabalho descreve o ingresso e a mortalidade em uma floresta em diferentes estágios sucessionais, no município de Castanhal, Pará. A área de estudo está localizada na Estação Experimental da Universidade Federal Rural da Amazônia. As parcelas foram implantadas em áreas de florestas sucessionais de diferentes idades (4, 8 e 12 anos). Nas florestas sucessionais de 4 e 8 anos foram utilizadas quatro parcelas de 10m x 10m e na floresta de 12 anos foram, 12 parcelas de 10m x 10m. Realizaram duas medições de todos os indivíduos com DAP>1cm, em intervalos de 12 meses, nas florestas sucessionais de 4 e 8 anos; e intervalo de 18 meses na floresta de 12 anos. Foram calculadas as taxas de ingresso e de mortalidade. Na floresta de 4 anos o ingresso foi maior que a mortalidade. Nas florestas sucessionais de 8 e 12 anos as densidades diminuíram, perdendo mais indivíduos por mortalidade do que ganhando por ingresso. Lacistema pubescens, Myrcia silvatica, Vismia guianensis, Rollinia exsucca e Miconia ciliata apresentaram muitos indivíduos mortos nas florestas estudadas.