Intermediate-scale horizontal isoprene concentrations in the near-canopy forest atmosphere and implications for emission heterogeneity

The emissions, deposition, and chemistry of volatile organic compounds (VOCs) are thought to be influenced by underlying landscape heterogeneity at intermediate horizontal scales of several hundred meters across different forest subtypes within a tropical forest. Quantitative observations and scientific understanding at these scales, however, remain lacking, in large part due to a historical absence of canopy access and suitable observational approaches. Herein, horizontal heterogeneity in VOC concentrations in the nearcanopy atmosphere was examined by sampling from an unmanned aerial vehicle (UAV) flown horizontally several hundred meters over the plateau and slope forests in central Amazonia during the morning and early afternoon periods of the wet season of 2018. Unlike terpene concentrations, the isoprene concentrations in the near-canopy atmosphere over the plateau forest were 60% greater than those over the slope forest. A gradient transport model constrained by the data suggests that isoprene emissions differed by 220 to 330%from these forest subtypes, which is in contrast to a 0% difference implemented in most present-day biosphere emissions models (i.e., homogeneous emissions). Quantifying VOC concentrations, emissions, and other processes at intermediate horizontal scales is essential for understanding the ecological and Earth system roles of VOCs and representing them in climate and air quality models. © 2019 National Academy of Sciences. All rights reserved

Variability and antifungal activity of volatile compounds from Aniba rosaeodora Ducke, harvested from Central Amazonia in two different seasons

Finding new applications for the essential oils (EOs) of the branches and leaves of Aniba species represents a valuable strategy for the adoption of correct management of the crown and to help make Aniba plantations economically valuable. We report here the antifungal activity of the EO from Aniba rosaeodora Ducke against plant pathogenic fungi. The present study investigated the chemical variability and antifungal effect of EO from A. rosaeodora harvested during the wet and dry seasons in the Amazon region. The volatile content obtained from the aerial parts by hydro-distillation was analyzed for its chemical composition by gas chromatography–mass spectrometry (GC–MS). Furthermore, a broth and agar dilution method was used to determine the antifungal activity against phytopathogens. Quantitative and qualitative variations in composition among the EOs were detected. Linalool was a major component in the oil of leaves and branches from both periods. Quantification using an external standard showed a higher concentration of linalool in the wet season (74.4 ± 3.9% in leaves and 81.8 ± 5.7% in branches) than in the dry season (47.5 ± 2.2 in leaves and 49.2 ± 1.6% in branches). The EOs were toxic to all phytopathogens analyzed, displaying superior inhibitory activity toward Colletotrichum guaranicola, with inhibition zone diameters ranging from 15.2 ± 1.2 to 21.3 ± 1.7 mm and IC50 values of 0.578 to 2.094 μL mL−1. Interestingly, the EOs collected during the wet season were effective in reducing the vegetative growth of phytopathogens, providing evidence for the involvement of linalool in the inhibitory effect. © 2018 Elsevier B.V

Biomass burning and carbon monoxide patterns in Brazil during the extreme drought years of 2005, 2010, and 2015

In the 21st century, severe droughts associated with climate change will increase biomass burning (BB) in Brazil caused by the human activities. Recent droughts, especially in 2005, 2010, and 2015, caused strong socioeconomic and environmental impacts. The 2015 drought considered the most severe since 1901, surpassed the 2005 and 2010 events in respect to area and duration. Herein, based on satellite data, the 2005, 2010 and 2015 drought impacts on wildfire episodes and carbon monoxide (CO) variability during the dry and the dry-to-wet transition seasons were examined. The BB occurrences in the dry season were fewer during 2015 than during 2005 (−44%) and 2010 (−47%). Contrasting, the BB events in the dry-to-wet transition season, were higher during 2015 than during 2005 (+192%) and 2010 (+332%). The BB outbreaks were concentrated in the southern and southwestern Amazon during 2005, in the Cerrado region during 2010, and mainly in the central and northern Amazon during 2015, an area normally with few fires. The CO concentration showed positive variations (up to +30%) occurred in the southern Amazon and central Brazil during the 2005 and 2010 dry seasons, and north of 20 °S during the 2015–2016 dry-to-wet transition season. The BB outbreaks and the CO emissions showed a considerable spatiotemporal variability among the droughts of 2005, 2010, and 2016, first of them driven by local conditions in the tropical North Atlantic (TNA), characterized by warm than normal sea surface waters and the other two by the El Niño occurrences. For the 2015 drought, the number of BB events remained high during the dry-to-wet transition season and affected northern regions where fires are normally few. © 2018 Elsevier Lt