Dinâmica da avifauna em áreas de borda da Mata Atlântica, Rio Grande do Sul

Birds serve as biological indicators, providing important ecosystem services such as aiding in seed dispersal, pollination, decomposition, thus being important for understanding the ecosystem dynamics. This study proposed to characterize the community structure of bird assemblages in forest edge areas in the Atlantic forest. Monthly surveys were performed between October 2008 and September 2009. We used the methodology of fixed points to sample birds in a 10 minute period/point. A hundred eighteen bird species were registered, which were distributed in 99 genera and 45 families. The sample areas showed similar species diversity. We observed three endemic species of the Atlantic Forest, such as Veniliornis spilogaster, Trogon surrucura and Procnias nudicollis (endangered). There were significant differences in species richness among seasons (F1,2=12,332; gl=2; p<0,05), with the highest richness value in winter in area 1. Insectivores, granivores and omnivores were the most frequent guilds, but specialized bird species, such as frugivorous and trunk insectivorous, were most frequent in area 3, which is considered a well conserved area. The study areas represent a transition between native forest and open environments providing diverse important habitats for conservation of bird assemblages.Keywords: anthropogenic environments, bird community, feeding guilds.Aves são indicadoras de qualidade ambiental, atuando na dispersão de sementes, na polinização e no consumo de material em decomposição, sendo importantes para o entendimento da dinâmica dos ecossistemas. No presente estudo, caracteriza-se a estrutura da comunidade de aves em áreas de borda florestal na Mata Atlântica. Foram realizadas amostragens mensais entre outubro/2008 e setembro/2009. Utilizou-se o método de pontos fixos para amostragem das aves durante 10 minutos/ponto. Foram registradas 118 espécies de aves, distribuídas em 99 gêneros e 45 famílias. As áreas apresentaram-se similares quanto à diversidade de espécies. Foram encontradas espécies endêmicas de Mata Atlântica, tais como Veniliornis spilogaster, Trogon surrucura e Procnias nudicollis (ameaçada de extinção). Houve diferença significativa na riqueza de espécies entre as estações do ano (F1,2=12,332; gl=2; p<0,05), com a maior riqueza de espécies registrada na área 1, no inverno. Insetívoros, granívoros e onívoros foram as guildas com maior frequência de ocorrência, sendo que espécies de aves especialistas, tais como frugívoras e insetívoras de tronco, foram mais frequentes na área 3, considerada uma área em bom estado de conservação. As áreas estudadas representam zonas de transição entre mata nativa e ambientes antropizados, com atividades agrícolas, propiciando diferentes hábitats importantes para a conservação de assembleias de aves.Palavras-chave: ambientes antropizados, comunidade de aves, guildas alimentares

Listening to tropical forest soils

Acoustic monitoring has proven to be an effective tool for monitoring biotic soundscapes in the marine, terrestrial, and aquatic realms. Recently it has been suggested that it could also be an effective method for monitoring soil soundscapes, but has been used in very few studies, primarily in temperate and polar regions. We present the first study of soil soundscapes using passive acoustic monitoring in tropical forests, using a novel analytical pipeline allowing for the use of in-situ recording of soundscapes with minimal soil disturbance. We found significant differences in acoustic index values between burnt and unburnt forests and the first indications of a diel cycle in soil soundscapes. These promising results and methodological advances highlight the potential of passive acoustic monitoring for large-scale and long-term monitoring of soil biodiversity. We use the results to discuss research priorities, including relating soil biophony to community structure and ecosystem function, and the use of appropriate hardware and analytical techniques

Tree growth and stem carbon accumulation in human-modified Amazonian forests following drought and fire

Human-modified forests are an ever-increasing feature across the Amazon Basin, but little is known about how stem growth is influenced by extreme climatic events and the resulting wildfires. Here we assess for the first time the impacts of human-driven disturbance in combination with El Niño–mediated droughts and fires on tree growth and carbon accumulation. We found that after 2.5 years of continuous measurements, there was no difference in stem carbon accumulation between undisturbed and human-modified forests. Furthermore, the extreme drought caused by the El Niño did not affect carbon accumulation rates in surviving trees. In recently burned forests, trees grew significantly more than in unburned ones, regardless of their history of previous human disturbance. Wood density was the only significant factor that helped explain the difference in growth between trees in burned and unburned forests, with low wood–density trees growing significantly more in burned sites. Our results suggest stem carbon accumulation is resistant to human disturbance and one-off extreme drought events, and it is stimulated immediately after wildfires. However, these results should be seen with caution—without accounting for carbon losses, recruitment and longer-term changes in species composition, we cannot fully understand the impacts of drought and fire in the carbon balance of human-modified forests. This article is part of a discussion meeting issue ‘The impact of the 2015/2016 El Nino on the terrestrial tropical carbon cycle: patterns, mechanisms and implications’

Quantifying immediate carbon emissions from El Nino-mediated wildfires in humid tropical forests

Wildfires produce substantial CO2 emissions in the humid tropics during El Niño-mediated extreme droughts, and these emissions are expected to increase in coming decades. Immediate carbon emissions from uncontrolled wildfires in human-modified tropical forests can be considerable owing to high necromass fuel loads. Yet, data on necromass combustion during wildfires are severely lacking. Here, we evaluated necromass carbon stocks before and after the 2015–2016 El Niño in Amazonian forests distributed along a gradient of prior human disturbance. We then used Landsat-derived burn scars to extrapolate regional immediate wildfire CO2 emissions during the 2015–2016 El Niño. Before the El Niño, necromass stocks varied significantly with respect to prior disturbance and were largest in undisturbed primary forests (30.2 ± 2.1 Mg ha−1, mean ± s.e.) and smallest in secondary forests (15.6 ± 3.0 Mg ha−1). However, neither prior disturbance nor our proxy of fire intensity (median char height) explained necromass losses due to wildfires. In our 6.5 million hectare (6.5 Mha) study region, almost 1 Mha of primary (disturbed and undisturbed) and 20 000 ha of secondary forest burned during the 2015–2016 El Niño. Covering less than 0.2% of Brazilian Amazonia, these wildfires resulted in expected immediate CO2 emissions of approximately 30 Tg, three to four times greater than comparable estimates from global fire emissions databases. Uncontrolled understorey wildfires in humid tropical forests during extreme droughts are a large and poorly quantified source of CO2 emissions. This article is part of a discussion meeting issue ‘The impact of the 2015/2016 El Niño on the terrestrial tropical carbon cycle: patterns, mechanisms and implications’