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Hidroquimica Dos Corpos De Águas Do Rio Madeira E Afluentes Na Area Proxima A Uhe Jirau/Ro.
No full textLong-term effect of selective logging on floristic composition: A 25 year experiment in the Brazilian Amazon
No full textSelective logging is one of the most prominent land uses in tropical forests and although it involves harvesting a limited number of trees, the impact on forest structure, composition and aboveground biomass can be significant. Although these impacts are well documented, what is little known is the extent to which selective logging affects tree floristic composition and its recovery process. Understanding how floristic composition is affected by logging activities is essential for determining subsequent cutting cycles, for the maintenance of carbon stocks and for biodiversity conservation. This research investigates the effect of logging on long-term trends on the recovery of species composition in a tropical forest using a unique logging experiment where measurements have been taken annually over a period of 25 years. Changes in 12 long-term 1-hectare (ha) permanent plots were assessed where different selective logging intensities occurred. In the first years after logging, floristic composition differed widely between intact and selectively logged forests, with exploited areas deviating from pre-logged composition. Over time, exploited areas shifted towards the original composition, with more pronounced changes in this trend after ∼13 years. Shifts in floristic composition were caused mainly by a significant increase in light-demanding fast-growing pioneer species and their subsequent continuous high mortality rates after 13 years of the recovery process. In contrast, the control plots showed similar shifts in composition over time, suggesting external factors such as long-term climate changes may be driving these shifts. The results suggest that 25 years after an experimental selective logging has taken place, floristic composition tends to recover closer to the pre-logged status. Thus, in the absence of further human disturbances, experimental selectively logged forests in low to moderate intensities are compatible with biodiversity conservation, at least during the first cycle of exploitation. Reconciling conservation strategies with the recovery of stocks of commercial timber species would be greatly improved by using these results and lead towards more sustainable forest management plans. © 2019 Elsevier B.V
Reassimilation of leaf internal CO2 contributes to isoprene emission in the neotropical species inga edulis Mart
Get PDFIsoprene (C5H8) is a hydrocarbon gas emitted by many tree species and has been shown to protect photosynthesis under abiotic stress. Under optimal conditions for photosynthesis, ~70%-90% of carbon used for isoprene biosynthesis is produced fromrecently assimilated atmospheric CO2. While the contribution of alternative carbon sources that increase with leaf temperature and other stresses have been demonstrated, uncertainties remain regarding the biochemical source(s) of isoprene carbon. In this study, we investigated leaf isoprene emissions (Is) from neotropical species Inga edulis Mart. as a function of light and temperature under ambient (450 μmol m-2 s-1) and CO2-free (0 μmol m-2 s-1) atmosphere. Is under CO2-free atmosphere showed light-dependent emission patterns similar to those observed under ambient CO2, but with lower light saturation point. Leaves treated with the photosynthesis inhibitor DCMU (3-(3,4-dichlorophenyl)-1,1-dimethylurea) failed to produce detectable Is in normal light under a CO2-free atmosphere. While strong temperature-dependent Is were observed under CO2-free atmosphere in the light, dark conditions failed to produce detectable Is even at the highest temperatures studied (40 °C). Treatment of leaves with 13C-labeled sodium bicarbonate under CO2-free atmosphere resulted in Is with over 50% containing at least one 13C atom. Is under CO2-free atmosphere and standard conditions of light and leaf temperature represented 19% ± 7% of emissions under ambient CO2. The results show that the reassimilation of leaf internal CO2 contributes to Is in the neotropical species I. edulis. Through the consumption of excess photosynthetic energy, our results support a role of isoprene biosynthesis, together with photorespiration, as a key tolerance mechanism against high temperature and high light in the tropics. © 2019 by the authors
O impacto da presença de rios e área urbana no desenvolvimento de um sistema meteorológico de meso escala na Amazônia Central
Get PDFThe impact of urbanization on mesoscale meteorological phenomena has been a focus
from various researches. These have shown that urban areas change the spatial pattern
rainfall, and life cycle of the meteorological phenomenon. In the Amazon, large
Cities are typically bordered by rivers and areas of dense forest, which influence and
are influenced by mesoscale convective systems. Studies of how these large
cities, rivers and dense forest, impact the mesoscale phenomena have not yet been
explored. In this work, numerical experiments were performed to evaluate the effect of
the presence of rivers, forests and cities, as well as experiments to assess the impact
of the horizontal growth of the city at the crossing of a squall line(SL). The
results show the convective maximums of the SL are intensified in the passage
about the city. On the other hand, without city, a SL entrance during its passage,
intensifying again after leaving the city. The absence of the river produced a more
early in the city and peaked after through the city. These experimental experiments that are not just the urban effect are responsible intensification of the SL over a city, and that co-dependence with the river influences a distribution and amount of rain. Already with urban expansion there is reduction of cloudiness over a city, which increases the surface pollution balance and changes the patterns of power partitioning. Positive thermal anomaly, imposed by the expansion of the city It is transported to higher levels of the atmosphere and current below the city. This one process, induces or weakens convective activities on the urban surface
leading to reduced accumulation of rain. The combination of impacts caused by
urban sprawl, adds to the diversity of the different types of surface coverage,
in changing local circulations. This change shifts convective activity to far away from the urbanization area in a fast growing city scenario. The effect thermal growth of the urban area also adds to the mechanical effect that leads to formation of an obstruction zone, which makes it difficult to maintain convective systems about the city. In addition, rivers impact or propagation direction of SL after the passage about the city. These results contribute to the understanding of the role of rivers and cities about the development of a SL in the Central Amazon, and shows the refinement of tiles in numerical experiments are fundamental for the representation of interactions between the system and the surface.O impacto da urbanização sobre fenômenos meteorológicos de mesoescala tem sido foco
de diversas pesquisas. Estas têm mostrado que áreas urbanas modificam o padrão espacial
e o volume chuva, e o ciclo de vida do fenômeno meteorológico. Na Amazônia, as grandes
cidades são tipicamente margeadas por rios e áreas de floresta densa, que influenciam e
são influenciadas por sistemas convectivos de mesoescala. Estudos de como estas grandes
cidades, rios e floresta densa, impactam os fenômenos de mesoescala ainda não foram
explorados. Neste trabalho foram realizados experimentos numéricos para avaliar o efeito
da presença de rios, floresta e cidade, como também experimentos para avaliar o impacto
do crescimento horizontal da cidade na passagem de uma linha de instabilidade (LI). Os
resultados mostram que os máximos convectivos da LI são intensificados na passagem
sobre a cidade. Por outro lado, sem a cidade, a LI enfraquece durante sua passagem,
voltando a se intensificar após deixar a cidade. A ausência do rio produziu uma LI mais
fraca, que chegou antecipadamente à cidade e atingiu máximo convectivo após passagem
pela cidade. Estes experimentos mostraram que não apenas o efeito urbano é responsável
pela intensificação da LI sobre a cidade, e que a co-dependência com o rio influencia a
distribuição e quantidade de chuva. Já com a expansão urbana há redução da nebulosidade
sobre a cidade, o que aumenta o saldo de radiação à superfície e modifica os padrões de
particionamento de energia. Anomalia positiva térmica, imposta pela expansão da cidade
é transportada para níveis mais altos da atmosfera e corrente abaixo da cidade. Este
processo, induz o enfraquecimento de atividades convectivas sobre a superfície urbana
levando a redução do acumulado de chuva. A combinação dos impactos provocados pela
expansão urbana, se somam à diversidade dos diferentes tipos de cobertura da superfície,
na mudança das circulações locais. Essa alteração desloca a atividade convectiva para
longe da área de urbanização em um cenário de forte crescimento da cidade. O efeito
térmico do crescimento da área urbana também se soma ao efeito mecânico que conduz a
formação de uma zona de obstrução, que dificulta a manutenção de sistemas convectivos
sobre a cidade. Ademais, os rios impactam o sentido de propagação da LI após passagem
sobre a cidade. Estes resultados contribuem para compreensão do papel de rios e cidades
sobre o desenvolvimento de uma LI na Amazônia Central, e mostra que o refinamento de
escalas nos experimentos numéricos são fundamentais para a representação das interações
entre o sistema e a superfície
Soil Carbon is Decreasing under “Undisturbed” Amazonian Forest
No full textWarming climate can cause release of carbon stocks in soils, but direct observations in tropical soils have been lacking. A unique data set from a study near Manaus, Brazil, allows comparison of samples taken before and after a ∼28-yr period in 176 plots in undisturbed forest (i.e., intact forest with no visible sign of modern human action and >100 m from a forest edge, with 98% of the plots being >300 m from an edge). The data indicate a significant loss of carbon in the top 20 cm of soil (2.98 MgC ha-1 over 28 yr, an average of 0.11 Mg ha-1 yr-1, or 0.3828% yr-1 of the carbon stock). Carbon emissions would be substantial if the pattern for the top 20 cm at this location holds throughout Amazonia, and the implications are huge if the same pattern holds for the deeper soil layers. Release of soil carbon can contribute to a positive feedback, where emissions cause greater warming that further augments the emissions. © 2019 The Author(s). Re-use requires permission from the publishe
Herbáceas Aquáticas em Igapós de Água Preta Dentro e Fora de Unidades de Conservação no Estado do Amazonas
No full textDecline of fine suspended sediments in the Madeira River basin (2003-2017)
Get PDFThe Madeira River is the second largest Amazon tributary, contributing up to 50% of the Amazon River's sediment load. The Madeira has significant hydropower potential, which has started to be used by the Madeira Hydroelectric Complex (MHC), with two large dams along the middle stretch of the river. In this study, fine suspended sediment concentration (FSC) data were assessed downstream of the MHC at the Porto Velho gauging station and at the outlet of each tributary (Beni and Mamoré Rivers, upstream from the MHC), from 2003 to 2017. When comparing the pre-MHC (2003-2008) and post-MHC (2015-2017) periods, a 36% decrease in FSC was observed in the Beni River during the peak months of sediment load (December-March). At Porto Velho, a reduction of 30% was found, which responds to the Upper Madeira Basin and hydroelectric regulation. Concerning water discharge, no significant change occurred, indicating that a lower peak FSC cannot be explained by changes in the peak discharge months. However, lower FSCs are associated with a downward break in the overall time series registered at the outlet of the major sediment supplier-the Beni River-during 2010. © 2019 by the authors
A new species of ami pérez-miles, 2008 (Araneae: Mygalomorphae: Theraphosidae) from the amazon rainforest, Brazil
Get PDFA new species of Ami Pérez-Miles, 2008 is described from the state of Amazonas in Brazil based on three males from Manaus. Ami valentinae sp. nov. is closely related to A. armihuariensis and A. caxiuana by the presence of a granular area on the embolus, but it differs from the first species by the presence of two retrolateral process on the male palpal tibia and differs by the latter by the morphology of the male palpal organ. A. valentinae sp. nov. is the first species of Ami reported for the Amazonas state and second species described for Brazil. © TÜBİTAK
