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Search Results: 1 - 10 of 563439 matches for " L. E. O. C. Arag o "
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Influence of landscape heterogeneity on spatial patterns of wood productivity, wood specific density and above ground biomass in Amazonia
L. O. Anderson,Y. Malhi,R. J. Ladle,L. E. O. C. Arago
Biogeosciences Discussions , 2009,
Abstract: Long-term studies using the RAINFOR network of forest plots have generated significant insights into the spatial and temporal dynamics of forest carbon cycling in Amazonia. In this work, we map and explore the landscape context of several major RAINFOR plot clusters using Landsat ETM+ satellite data. In particular, we explore how representative the plots are of their landscape context, and test whether bias in plot location within landscapes may be influencing the regional mean values obtained for important forest biophysical parameters. Specifically, we evaluate whether the regional variations in wood productivity, wood specific density and above ground biomass derived from the RAINFOR network could be driven by systematic and unintentional biases in plot location. Remote sensing data covering 45 field plots were aggregated to generate landscape maps to identify the specific physiognomy of the plots. In the Landsat ETM+ data, it was possible to spectrally differentiate three types of terra firme forest, three types of alluvial terrain forest, two types of bamboo-dominated forest, palm forest, Heliconia monodominant vegetation, swamp forest, disturbed forests and land use areas. Overall, the plots were generally representative of the forest physiognomies in the landscape in which they are located. Furthermore, the analysis supports the observed regional trends in those important forest parameters. This study demonstrates the utility of landscape scale analysis of forest physiognomies for validating and supporting the finds of plot based studies. Moreover, the more precise geolocation of many key RAINFOR plot clusters achieved during this research provides important contextual information for studies employing the RAINFOR database.
Above- and below-ground net primary productivity across ten Amazonian forests on contrasting soils
L. E. O. C. Arago,Y. Malhi,D. B. Metcalfe,J. E. Silva-Espejo
Biogeosciences Discussions , 2009,
Abstract: The net primary productivity (NPP) of tropical forests is one of the most important and least quantified components of the global carbon cycle. Most relevant studies have focused particularly on the quantification of the above-ground coarse wood productivity, and little is known about the carbon fluxes involved in other elements of the NPP, the partitioning of total NPP between its above- and below-ground components and the main environmental drivers of these patterns. In this study we quantify the above- and below-ground NPP of ten Amazonian forests to address two questions: (1) How do Amazonian forests allocate productivity among its above- and below-ground components? (2) How do soil and leaf nutrient status and soil texture affect the productivity of Amazonian forests? Using a standardized methodology to measure the major elements of productivity, we show that NPP varies between 9.3±1.3 Mg C ha 1 yr 1 (mean±standard error), at a white sand plot, and 17.0±1.4 Mg C ha 1 yr 1 at a very fertile Terra Preta site, with an overall average of 12.8±0.9 Mg C ha 1 yr 1. The studied forests allocate on average 64±3% and 36±3% of the total NPP to the above- and below-ground components, respectively. The ratio of above-ground and below-ground NPP is almost invariant with total NPP. Litterfall and fine root production both increase with total NPP, while stem production shows no overall trend. Total NPP tends to increase with soil phosphorus and leaf nitrogen status. However, allocation of NPP to below-ground shows no relationship to soil fertility, but appears to decrease with the increase of soil clay content.
Assessing the Influence of Climate Extremes on Ecosystems and Human Health in Southwestern Amazon Supported by the PULSE-Brazil Platform  [PDF]
L. E. O. C. Arago, J. A. Marengo, P. M. Cox, R. A. Betts, D. Costa, N. Kaye, L. Alves, L. T. Smith, I. F. A. Cavalcanti, G. Sampaio, L. O. Anderson, M. Horta, S. Hacon, V. L. Reis, P. A. M. Fonseca, I. F. Brown
American Journal of Climate Change (AJCC) , 2016, DOI: 10.4236/ajcc.2016.53030
Abstract: The complexity of multi-dimensional climate, environmental and human health information complicates bringing together scientists, civil society, and decision makers to provide adequate mitigation and adaptation options for the consequences of global environmental change. To provide an effective pathway to conciliate (integrate) these datasets, we present PULSE-Brazil as the Platform for Understanding Long-term Sustainability of Ecosystems and human health. The overarching aim of this paper is to focus on two study cases in the Brazilian state of Acre, 1) analyzing recent socio-environmental disasters such as the impacts of droughts and consequent increases in fire detections on the incidence of respiratory diseases, and 2) evaluating the impacts of temperature increases in combination with rainfall seasonality upon the incidence of Dengue fever. Based on data available in PULSE-Brazil platform, we also aim to provide insights on the consequences of future climate variability on ecosystems and human health. Finally, we provide a discussion on the collaborative process between scientists and policymakers that defined the PULSE-Brazil platform specifications and datasets and propose a conceptual pathway for promoting the interaction between science and policy during the process of producing a tool that allows the understating of climate-relate processes. Our results clearly demonstrated that ecosystems are under increased fire risk in the future that will, in turn, affect the health of human populations. Moreover, humans are also exposed to critical Dengue fever outbreaks with the projected increase in minimum temperatures. Therefore, minimizing the impacts of these potentially ascending socio-environmental problems is the first step for adapting to a changing climate in the Amazon region. We expect that PULSE-Brazil will serve not only as a technical tool for supporting governance, management, mitigation and long-term adaptation plans for climate impacts and natural disasters, but also will take advantage of its graphical capabilities to be an instructive vehicle that facilitates information flow for societal governance.
The dynamics of cultivation and floods in arable lands of Central Argentina
E. F. Viglizzo, E. G. Jobbágy, L. Carre o, F. C. Frank, R. Aragón, L. De Oro,V. Salvador
Hydrology and Earth System Sciences (HESS) & Discussions (HESSD) , 2009,
Abstract: Although floods in watersheds have been associated with land-use change since ancient times, the dynamics of flooding is still incompletely understood. In this paper we explored the relations between rainfall, groundwater level, and cultivation to explain the dynamics of floods in the extremely flat and valuable arable lands of the Quinto river watershed, in central Argentina. The analysis involved an area of 12.4 million hectare during a 26-year period (1978–2003), which comprised two extensive flooding episodes in 1983–1988 and 1996–2003. Supported by information from surveys as well as field and remote sensing measurements, we explored the correlation among precipitation, groundwater levels, flooded area and land use. Flood extension was associated to the dynamics of groundwater level. While no correlation with rainfall was recorded in lowlands, a significant correlation (P<0.01) between groundwater and rainfall in highlands was found when estimations comprise a time lag of one year. Correlations between groundwater level and flood extension were positive in all cases, but while highly significant relations (P<0.01) were found in highlands, non significant relations (P>0.05) predominate in lowlands. Our analysis supports the existence of a cyclic mechanism driven by the reciprocal influence between cultivation and groundwater in highlands. This cycle would involve the following stages: (a) cultivation boosts the elevation of groundwater levels through decreased evapotranspiration; (b) as groundwater level rises, floods spread causing a decline of land cultivation; (c) flooding propitiates higher evapotranspiration favouring its own retraction; (d) cultivation expands again following the retreat of floods. Thus, cultivation would trigger a destabilizing feedback self affecting future cultivation in the highlands. It is unlikely that such sequence can work in lowlands. The results suggest that rather than responding directly and solely to the same mechanism, floods in lowlands may be the combined result of various factors like local rainfall, groundwater level fluctuations, surface and subsurface lateral flow, and water-body interlinking. Although the hypothetical mechanisms proposed here require additional understanding efforts, they suggest a promising avenue of environmental management in which cultivation could be steered in the region to smooth the undesirable impacts of floods.
Immune response induced in mice oral immunization with cowpea severe mosaic virus
Florindo M.I.,Arago M.E.F. de,Silva A.C.M. da,Otoch M.L.
Brazilian Journal of Medical and Biological Research , 2002,
Abstract: There is increasing interest in the immune response induced by plant viruses since these could be used as antigen-expressing systems in vaccination procedures. Cowpea severe mosaic virus (CPSMV), as a purified preparation (300 g of leaves, 2 weeks post-inoculation), or crude extract from cowpea (Vigna unguiculata) leaves infected with CPSMV both administered by gavage to Swiss mice induced a humoral immune response. Groups of 10 Swiss mice (2-month-old females) were immunized orally with 10 daily doses of either 50 μg viral capsid protein (boosters of 50 μg at days 21 and 35 after immunization) or 0.6 mg protein of the crude extract (boosters of 0.6 mg at days 21 and 35 after immunization). Anti-CPSMV antibodies were quantified by ELISA in pooled sera diluted at least 1:400 at days 7, 14, 21, 28, 35 and 42 after the 10th dose. IgG and IgA against CPSMV were produced systemically, but IgE was not detected. No synthesis of specific antibodies against the proteins of leaf extracts from V. unguiculata, infected or not with CPSMV, was detected. The use of CPSMV, a plant-infecting virus that apparently does not induce a pathogenic response in animals, induced a humoral and persistent (at least 6 months) immune response through the administration of low antigen doses by gavage. These results raise the possibility of using CPSMV either as a vector for the production of vaccines against animal pathogens or in quick and easy methods to produce specific antisera for viral diagnosis.
Influence of landscape heterogeneity on spatial patterns of wood productivity, wood specific density and above ground biomass in Amazonia
L. O. Anderson, Y. Malhi, R. J. Ladle, L. E. O. C. Arag o, Y. Shimabukuro, O. L. Phillips, T. Baker, A. C. L. Costa, J. S. Espejo, N. Higuchi, W. F. Laurance, G. López-González, A. Monteagudo, P. Nú ez-Vargas, J. Peacock, C. A. Quesada,S. Almeida
Biogeosciences (BG) & Discussions (BGD) , 2009,
Abstract: Long-term studies using the RAINFOR network of forest plots have generated significant insights into the spatial and temporal dynamics of forest carbon cycling in Amazonia. In this work, we map and explore the landscape context of several major RAINFOR plot clusters using Landsat ETM+ satellite data. In particular, we explore how representative the plots are of their landscape context, and test whether bias in plot location within landscapes may be influencing the regional mean values obtained for important forest biophysical parameters. Specifically, we evaluate whether the regional variations in wood productivity, wood specific density and above ground biomass derived from the RAINFOR network could be driven by systematic and unintentional biases in plot location. Remote sensing data covering 45 field plots were aggregated to generate landscape maps to identify the specific physiognomy of the plots. In the Landsat ETM+ data, it was possible to spectrally differentiate three types of terra firme forest, three types of forests over Paleovarzea geomorphologycal formation, two types of bamboo-dominated forest, palm forest, Heliconia monodominant vegetation, swamp forest, disturbed forests and land use areas. Overall, the plots were generally representative of the forest physiognomies in the landscape in which they are located. Furthermore, the analysis supports the observed regional trends in those important forest parameters. This study demonstrates the utility of landscape scale analysis of forest physiognomies for validating and supporting the finds of plot based studies. Moreover, the more precise geolocation of many key RAINFOR plot clusters achieved during this research provides important contextual information for studies employing the RAINFOR database.
Regional and seasonal patterns of litterfall in tropical South America
J. Chave, D. Navarrete, S. Almeida, E. álvarez, L. E. O. C. Arag o, D. Bonal, P. Chatelet, J. E. Silva-Espejo, J.-Y. Goret, P. von Hildebrand, E. Jiménez, S. Pati o, M. C. Pe uela, O. L. Phillips, P. Stevenson,Y. Malhi
Biogeosciences (BG) & Discussions (BGD) , 2010,
Abstract: The production of aboveground soft tissue represents an important share of total net primary production in tropical rain forests. Here we draw from a large number of published and unpublished datasets (n=81 sites) to assess the determinants of litterfall variation across South American tropical forests. We show that across old-growth tropical rainforests, litterfall averages 8.61±1.91 Mg ha 1 yr 1 (mean ± standard deviation, in dry mass units). Secondary forests have a lower annual litterfall than old-growth tropical forests with a mean of 8.01±3.41 Mg ha 1 yr 1. Annual litterfall shows no significant variation with total annual rainfall, either globally or within forest types. It does not vary consistently with soil type, except in the poorest soils (white sand soils), where litterfall is significantly lower than in other soil types (5.42±1.91 Mg ha 1 yr 1). We also study the determinants of litterfall seasonality, and find that it does not depend on annual rainfall or on soil type. However, litterfall seasonality is significantly positively correlated with rainfall seasonality. Finally, we assess how much carbon is stored in reproductive organs relative to photosynthetic organs. Mean leaf fall is 5.74±1.83 Mg ha 1 yr 1 (71% of total litterfall). Mean allocation into reproductive organs is 0.69±0.40 Mg ha 1 yr 1 (9% of total litterfall). The investment into reproductive organs divided by leaf litterfall increases with soil fertility, suggesting that on poor soils, the allocation to photosynthetic organs is prioritized over that to reproduction. Finally, we discuss the ecological and biogeochemical implications of these results.
Above- and below-ground net primary productivity across ten Amazonian forests on contrasting soils
L. E. O. C. Arag o, Y. Malhi, D. B. Metcalfe, J. E. Silva-Espejo, E. Jiménez, D. Navarrete, S. Almeida, A. C. L. Costa, N. Salinas, O. L. Phillips, L. O. Anderson, E. Alvarez, T. R. Baker, P. H. Goncalvez, J. Huamán-Ovalle, M. Mamani-Solórzano, P. Meir, A. Monteagudo, S. Pati o, M. C. Pe uela, A. Prieto, C. A. Quesada, A. Rozas-Dávila, A. Rudas, J. A. Silva Jr.,R. Vásquez
Biogeosciences (BG) & Discussions (BGD) , 2009,
Abstract: The net primary productivity (NPP) of tropical forests is one of the most important and least quantified components of the global carbon cycle. Most relevant studies have focused particularly on the quantification of the above-ground coarse wood productivity, and little is known about the carbon fluxes involved in other elements of the NPP, the partitioning of total NPP between its above- and below-ground components and the main environmental drivers of these patterns. In this study we quantify the above- and below-ground NPP of ten Amazonian forests to address two questions: (1) How do Amazonian forests allocate productivity among its above- and below-ground components? (2) How do soil and leaf nutrient status and soil texture affect the productivity of Amazonian forests? Using a standardized methodology to measure the major elements of productivity, we show that NPP varies between 9.3±1.3 Mg C ha 1 yr 1 (mean±standard error), at a white sand plot, and 17.0±1.4 Mg C ha 1 yr 1 at a very fertile Terra Preta site, with an overall average of 12.8±0.9 Mg C ha 1 yr 1. The studied forests allocate on average 64±3% and 36±3% of the total NPP to the above- and below-ground components, respectively. The ratio of above-ground and below-ground NPP is almost invariant with total NPP. Litterfall and fine root production both increase with total NPP, while stem production shows no overall trend. Total NPP tends to increase with soil phosphorus and leaf nitrogen status. However, allocation of NPP to below-ground shows no relationship to soil fertility, but appears to decrease with the increase of soil clay content.
Spatial distribution and functional significance of leaf lamina shape in Amazonian forest trees
A. C. M. Malhado, R. J. Whittaker, Y. Malhi, R. J. Ladle, H. ter Steege, N. Butt, L. E. O. C. Arag o, C. A. Quesada, A. Murakami-Araujo, O. L. Phillips, J. Peacock, G. López-González, T. R. Baker, L. O. Anderson, L. Arroyo, S. Almeida, N. Higuchi, T. J. Killeen, A. Monteagudo, D. A. Neill, N. C. A. Pitman, A. Prieto, R. P. Salom o, R. Vásquez-M., W. F. Laurance,H. Ramírez A.
Biogeosciences (BG) & Discussions (BGD) , 2009,
Abstract: Leaves in tropical forests come in an enormous variety of sizes and shapes, each of which can be ultimately viewed as an adaptation to the complex problem of optimising the capture of light for photosynthesis. However, the fact that many different shape "strategies" coexist within a habitat demonstrate that there are many other intrinsic and extrinsic factors involved, such as the differential investment in support tissues required for different leaf lamina shapes. Here, we take a macrogeographic approach to understanding the function of different lamina shape categories. Specifically, we use 106 permanent plots spread across the Amazon rainforest basin to: 1) describe the geographic distribution of some simple metrics of lamina shape in plots from across Amazonia, and; 2) identify and quantify relationships between key environmental parameters and lamina shape in tropical forests. Because the plots are not randomly distributed across the study area, achieving this latter objective requires the use of statistics that can account for spatial auto-correlation. We found that between 60–70% of the 2791 species and 83 908 individual trees in the dataset could be classified as having elliptic leaves (= the widest part of the leaf is on an axis in the middle fifth of the long axis of the leaf). Furthermore, the average Amazonian tree leaf is 2.5 times longer than it is wide and has an entire margin. Contrary to theoretical expectations we found little support for the hypothesis that narrow leaves are an adaptation to dry conditions. However, we did find strong regional patterns in leaf lamina length-width ratios and several significant correlations with precipitation variables suggesting that water availability may be exerting an as yet unrecognised selective pressure on leaf shape of rainforest trees. Some support was found for the hypothesis that narrow leaves are an adaptation to low nutrient soils. Furthermore, we found a strong correlation between the proportion of trees with non-entire laminas (dissected, toothed, etc.) and mean annual temperature once again supporting the well documented association that provides a basis for reconstructing past temperature regimes.
The carbon balance of South America: a review of the status, decadal trends and main determinants
M. Gloor, L. Gatti, R. Brienen, T. R. Feldpausch, O. L. Phillips, J. Miller, J. P. Ometto, H. Rocha, T. Baker, B. de Jong, R. A. Houghton, Y. Malhi, L. E. O. C. Arag o, J.-L. Guyot, K. Zhao, R. Jackson, P. Peylin, S. Sitch, B. Poulter, M. Lomas, S. Zaehle, C. Huntingford, P. Levy,J. Lloyd
Biogeosciences (BG) & Discussions (BGD) , 2012,
Abstract: We summarise the contemporary carbon budget of South America and relate it to its dominant controls: population and economic growth, changes in land use practices and a changing atmospheric environment and climate. Component flux estimate methods we consider sufficiently reliable for this purpose encompass fossil fuel emission inventories, biometric analysis of old-growth rainforests, estimation of carbon release associated with deforestation based on remote sensing and inventories, and agricultural export data. Alternative methods for the estimation of the continental-scale net land to atmosphere CO2 flux, such as atmospheric transport inverse modelling and terrestrial biosphere model predictions, are, we find, hampered by the data paucity, and improved parameterisation and validation exercises are required before reliable estimates can be obtained. From our analysis of available data, we suggest that South America was a net source to the atmosphere during the 1980s (~ 0.3–0.4 Pg C a 1) and close to neutral (~ 0.1 Pg C a 1) in the 1990s. During the latter period, carbon uptake in old-growth forests nearly compensated for the carbon release associated with fossil fuel burning and deforestation. Annual mean precipitation over tropical South America as inferred from Amazon River discharge shows a long-term upward trend. Although, over the last decade dry seasons have tended to be drier, with the years 2005 and 2010 in particular experiencing strong droughts. On the other hand, precipitation during the wet seasons also shows an increasing trend. Air temperatures have also increased slightly. Also with increases in atmospheric CO2 concentrations, it is currently unclear what effect these climate changes are having on the forest carbon balance of the region. Current indications are that the forests of the Amazon Basin have acted as a substantial long-term carbon sink, but with the most recent measurements suggesting that this sink may be weakening. Economic development of the tropical regions of the continent is advancing steadily, with exports of agricultural products being an important driver and witnessing a strong upturn over the last decade.
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