Southwest Amazon Research Articles

Abundância do zooplâncton em diferentes zonas (pelágica e litorânea) e horários (manhã e noite) em dois lagos meândricos amazônicos

The abundance of zooplankton in two lakes of Southwest Amazonia was studied for 10 months in different regions and at different periods of the day. The lakes were Lago Amapa , located at 10°02'36''S, 67°50'24''W, and Lago Pirapora , at 9°27'21S, 67°31'39. Both lakes are characterized as oxbow lakes. The aim of this study was to compare the pelagic and littoral regions, as well as to determine differences in the distribution of zooplankton in the water column in the morning and at night. Collections were made by filtering water through a 55µm zooplankton net into a 5L Van Dorn bottle, collecting 4L from the top and 5L from the middle and bottom layers, totaling 14L of water for each sampling location. In addition, physical and chemical parameters were measured, including transparency, temperature, pH, dissolved oxygen, electrical conductivity and turbidity. Anova (analysis of variance) and Tukey’s test were used. There was no statistically significant difference between the regions studied, nor between the two time periods examined. The results of the Pearson correlation (p Moina spp. (represented by M. minuta and M. reticulate ) and Ceriodaphnia cornuta , and that Daphnia gessneri was associated with Chaoboridae

The South American low‐level jet east of the Andes during the 1999 LBA‐TRMM and LBA‐WET AMC campaign

The present study describes some observed surface and upper‐air features of the low‐level jet (LLJ) and southerly jet (SJ). Our results suggest the existence of this low‐level circulation to the east of the Andes that transports moisture from tropical South America toward the south during the warm/wet season of 1999. We explore the synoptic variability, diurnal variation, and alternations between LLJ and SJ episodes by using a combination of surface and high‐resolution upper‐air observations (1 to 8 soundings per day) and global reanalysis. Our results show strong synoptic fluctuations; with the LLJ more frequent than SJs. The LLJ has stronger winds in the afternoon and its core of maximum winds is located between 1600 and 2000 m above the surface. Special observational efforts, such as the pilot balloon sounding network in Bolivia (Pan American Climate Studies Sounding Network [PACS‐SONET] program), the Large‐Scale Biosphere‐Atmosphere (LBA) Experiment‐WET Atmospheric Mesoscale Campaign (AMC), and Tropical Rainfall Measuring Mission (TRMM)‐LBA in Southwest Amazonia, have provided upper‐air information with high temporal and spatial resolution to describe the structure of both the LLJ and the SJ during the January–April 1999 period.

A case study of convective organization into precipitating lines in the Southwest Amazon during the WETAMC and TRMM‐LBA

A case study of convective development in the Southwest Amazon region during the Wet Season Atmospheric Mesoscale Campaign (WETAMC) and Tropical Rainfall Measuring Mission (TRMM)/Large‐Scale Biosphere‐Atmosphere (LBA) Experiment in Amazonia is presented. The convective development during 7 February 1999 is shown to occur during a period of very weak large‐scale forcing in the presence of topography and deforestation. The available data include dual Doppler radar analysis, radiosonde launches, and surface and boundary layer observations. The observational analysis is complemented with a series of model simulations using the RAMS with 2‐km resolution over a 300 km × 300 km area forced by a morning radiosonde profile. A comparison of the observed and simulated thermodynamic transformation of the boundary layer and of the formation of convective lines, and of their kinematic and microphysical properties is presented. It is shown that only a few very deep and intense convective cells are necessary to explain the overall precipitating line formation and that discrete propagation and coupling with upper atmosphere circulations may explain the appearance of several lines. The numerical simulation indicates that topography may be the cause of initial convective development, although later on the convective line is parallel to the midlevel shear. There are indications that small‐scale deforestation may have an effect on increasing rainfall in the wet season when the large‐scale forcing is very weak.

Radar observations of the kinematic, microphysical, and precipitation characteristics of two MCSs in TRMM LBA

Dual‐Doppler and polarimetric radar observations are used to analyze two mesoscale convective systems (MCSs) that occurred during the Tropical Rainfall Measuring Mission Large‐Scale Biosphere‐Atmosphere field campaign. The MCSs formed in different meteorological regimes, based on profiles of atmospheric wind and thermodynamic data. The first MCS event (26 January 1999) was a squall line that formed in low‐level easterly flow and had an intense leading line of convection. In contrast, the 25 February 1999 MCS formed in low‐level westerly flow and was best characterized by stratiform precipitation with embedded convective elements. The radar analyses suggest that the MCSs were distinct in terms of overall vertical structure characteristics. In particular, polarimetric radar cross sections indicated the presence of an active mixed phase zone in the easterly MCS that was largely absent in the westerly case. The easterly MCS had considerably more precipitation ice in the middle to upper troposphere compared to the westerly MCS. Composite analyses showed that the easterly MCS had higher peak reflectivities and a smaller reflectivity gradient above the 0°C level in convective regions of the storm compared to the westerly MCS event. Moreover, mean profiles of both vertical air motion and vertical mass transport in the convective portion of the easterly MCS were larger (over a factor of 2 at some heights below the 0°C level) than those in the westerly event. These observations suggest that the easterly and westerly wind regimes in the southwest Amazon region produce convection with different vertical structure characteristics, similar to regimes elsewhere in the global tropics (e.g., maritime continent).

Rainfall estimation from TOGA radar observations during LBA field campaign

The TRMM Large Scale Biosphere‐Atmosphere (LBA) experiment, conducted between January and February of 1999 in Southwest Amazon, deployed among other instruments NASA's C‐band Doppler radar (TOGA) and four dense rain gauge networks. This paper presents a procedure devised to derive surface rainfall rate estimates from combination of TOGA observations and the in situ rain gauge rainfall measurements. The spatial and temporal scales considered are 2 × 2 km2 grids of instantaneous to hourly rain accumulations. The procedure includes evaluation of TOGA calibration through comparisons with TRMM Precipitation Radar (PR) data and implementation of an optimal quantitative precipitation estimation (QPE) algorithm. Comparisons with PR indicated a 4‐dB calibration offset occurring in the later two thirds of the observation period. The implemented QPE algorithm applies a parameter that differentiates the Z‐R conversion in convective and stratiform regimes and a stochastic filtering approach for estimation of mean‐field bias on the basis of radar‐rain gauge comparisons at the hourly timescale. The calibration of the algorithm parameter values is formulated as a global optimization problem, which is solved by minimizing the radar‐rain gauge rainfall accumulation root‐mean‐square (rms) difference at the hourly timescale. A random resampling calibration/validation exercise is performed to evaluate the algorithm performance and its sensitivity to parameter values. Validation against gauges shows that the algorithm produces unbiased estimates with ∼57% relative RMS difference at the hourly scale. Comparison with S‐POL rain estimates showed good correlation (0.9) but some overestimation (9%). Rainfall products are used to derive rainfall statistics for two distinct meteorological low‐level wind regimes (easterly and westerly) that occurred during LBA. Finally, instantaneous rain estimates are compared against TRMM PR rainfall profiles for six coincident storm cases showing high correlation (0.9) and low (7%) systematic difference (PR overestimation).

Scale variability of atmospheric surface layer fluxes of energy and carbon over a tropical rain forest in southwest Amazonia 1. Diurnal conditions

The aim of this study is to investigate the low‐frequency characteristics of diurnal turbulent scalar spectra and cospectra near the Amazonian rain forest during the wet and dry seasons. This is because the available turbulent data are often nonstationary and there is no clear spectral gap to separate data into “mean” and “turbulent” parts. Daubechies‐8 orthogonal wavelet is used to scale project turbulent signals in order to provide scale variance and covariance estimations. Based on the characteristics of the scale dependence of the scalar fluxes, some classification criteria of this scale dependence are investigated. The total scalar covariance of each 4‐hour data run is partitioned in categories of scale covariance contributions. This permits the study of some statistical characteristics of the scalar turbulent fields in each one of these classes and, thus, to give an insight and a possible explanation of the origin of the variability of the scalar fields close to the Amazonian forest. The results have shown that a two‐category classification is the most appropriate to describe the kind of observed fluctuations: “turbulent” and “mesoscale” contributions. The largest contribution of the sensible heat, latent heat, and CO2 covariance contributions occurs in the “turbulent” length scales. Mesoscale eddy motions, however, can contribute up to 30% of the total covariances under weak wind conditions. Analysis of scale correlation coefficient [r(Tvq)] between virtual temperature (Tv) and humidity (q) signals shows that the scale patterns of Tv and q variability are not similar and r(Tvq) < 1 for all analyzed scales. Scale humidity skewness calculations are negative during the dry season and positive during the wet season. This suggests that different boundary layer moisture regimes occur during the dry and wet seasons.

Measurements of drop size distribution in the southwestern Amazon basin

Simultaneous observations of an optical and an impact type disdrometer and their application in radar rainfall estimation are evaluated. The disdrometers and two collocated rain gauges were operated in the southwest Amazon region of Brazil in 1999 as part of a NASA Tropical Rainfall Measuring Mission (TRMM) field campaign and the hydro‐meteorological component of the Large Scale Biosphere–Atmosphere Experiment (LBA). During the experiment, we observed large drops with diameters greater than 5 mm. These large drops were not adequately detected by the impact disdrometer and resulted in differences in drop size distribution and integral rain parameters derived from the two sensors. Considering coincident observations, we calculated that the impact disdrometer recorded about 11% lower rainfall accumulations than the optical disdrometer. In addition, radar rainfall algorithms, which we derived from the impact and optical disdrometer measurements, showed instrument dependency. Out of four radar rainfall algorithms that we considered, rain rate derived from specific differential phase has the least dependency, while the rain rate derived from reflectivity at horizontal polarization and differential reflectivity combined exhibited the largest. We also observed the characteristics of rainfall and drop size distribution in two distinct wind regimes present during the TRMM–LBA field campaign. Rain was heavier in the easterly regime, with more large drops being present.

Cosmic reproduction, economics and politics among the Kulina of Southwest Amazonia

Kulina cosmology legitimates the monopoly of the mystical means of reproduction by male shamans and leaders. This control is accompanied by a degree of manipulation of female sexuality and reproduction by shamanic and other means. It is also correlated with a hierarchical division of labour in which men are primary providers, and leaders are paradigmatic providers. This calls into question the commonly angelic or neo‐Rousseauist vision of the indigenous societies of the Amazon as egalitarian.

Variation in Nutrient Distribution and Potential Nutrient Losses by Selective Logging in a Humid Tropical Forest of Rondônia, Brazil1

Despite having one of the world's highest deforestation rates, the tropical forest of Rondonia state in the southwest Amazon is virtually unknown in terms of nutrient dynamics. To fill this knowledge gap, the distribution of nutrients in a humid tropical forest located in the Ecological Reserve of Samuel, Rondonia state, was addressed. A total of 474 trees with diameter at breast height (DBH) >10 cm were mapped at the Ecological Reserve of Samuel, a 20,000-ha area bordering the Samuel Hydroelectric Reservoir, which is located 50 km south of Porto Velho, Rondonia state, Amazon region, Brazil. These individuals belonged to ca 220 species distributed in 41 families. From this total, leaves of 354 trees were collected for chemical compositional analysis; boles of 96 trees and fine branches of 75 trees also were collected. Soil samples were gathered for fertility analysis at two soil depth intervals: 0–50 and 50–100 cm. In general, soils were acidic and very poor in terms of elemental contents. For plants, the highest concentrations of P, K, and Mg were found in leaves and fine branches, and the highest concentration of Ca was in the litter. The lowest nutrient concentration was observed in boles. The nutrient concentrations of leaves collected at Samuel were similar to that found in other terra firme forests of the Amazon region and other tropical forests growing on poor soils. Comparisons of nutrient concentrations among families, genera, and species revealed that only N concentrations were distinct among botanical taxa; the variability found in concentrations of other nutrients were larger and did not reveal any significant differences. Like aboveground biomass, the total nutrient stocks of trees was concentrated in a few large individuals. This fact reveals important implications about the impacts caused by selective logging. Although few trees are cut per hectare in this activity, the effects on the ecosystem structure, due to the loss of nutrients, may be underestimated.

Mapping the regional extent of tropical forest regeneration stages in the Brazilian Legal Amazon using NOAA AVHRR data

The study aimed to map several stages of tropical forest regeneration across the Brazilian Legal Amazon using 1.1 km NOAA AVHRR data. Regenerating forest extent was defined using an unsupervised classification of AVHRR channels 1, 2 and 3 and the Global Environment Monitoring Index (GEMI). A method for discriminating four forest regeneration stages was then developed, based on relationships between AVHRR channels 1, 2 and 3 and forest age. This method was applied to AVHRR data to map forests associated with Stages I (early colonization phase, open canopy, < 5 years), II (closed, singlelayered canopy, 5-9 years), III (closed canopy with structural development, 9-20 years) and IV (closed multilayered canopy, > 20 years). The maps provided new regional estimates of regenerating forest for the Legal Amazon and indicated that, over the period 1991 to 1994, approximately 35.8% (157 973 km2) of the total deforested area of 440 186 km2 (estimated for 1992) supported regenerating forest, with 48% of these forests aged at less than 5 years. The study concluded that AVHRR data has an important role in mapping and monitoring tropical forest regeneration. The datasets generated provide valuable input to models of regional carbon flux. For example, Grace et al . (1995a, b) reported net annual CO2 absorption 8.5 2.0 moles m 2 for mature forests in south-west Amazonia suggesting

Palmeiras do Parque Natural do Seringueiro, Acre, Brasil

Dez gêneros e vinte e duas espécies de palmeiras foram encontradas no Parque Natural do Seringueiro, localizado no Município de Plácido de Castro (AC), sudoeste da Amazônia (10 20'S, 67 15,W). Embora contando com uma área de apenas 45 hectares a diversidade de gêneros e espécies é comparável à encontrada nos 10.000 hectares da Reserva Ducke, na Amazônia central. A alta diversidade verificada, combinada com a elevada taxa de destruição da cobertura vegetal na região de Plácido de Castro, demonstram a urgente necessidade de se estabelecer novas áreas de proteção para a flora local.

Total Reactive Antioxidant Potential (TRAP) and Total Antioxidant Reactivity (TAR) of Medicinal Plants Used in Southwest Amazonia (Bolivia and Peru)

The charge (relative concentration) of antioxidants in different extracts of medicinal plants used in southwest Amazonia regions of Beni (Bolivia) and Madre de Dios (Peru) was determined employing a procedure based on the quenching of luminol-enhanced chemiluminescence derived from the thermolysis of 2,2'-azo- bis (2-amidinopropane) (ABAP) as the free radical source. Total reactive antioxidant potential (TRAP) and total antioxidant reactivity (TAR) values were determined (in Trolox equivalents) using this method, and 65 extracts showed antioxidant activity. Of these, 46 demonstrated TRAP values > 100 µM. The highest activity was noted in a methanol bark extract of Copaifera reticulata (TRAP = 7500 µM). On the other hand, the highest TAR value was obtained in the methanol root extract of Dracontium loretense. IC 50 and eficiency (compared to Trolox) values were also calculated. The results obtained indicate that the large antioxidant capacity of some medicinal plants may be due to the presence of both v...

Comparison of the detection of deforested areas using the ERS-1 ATSR and the NOAA-11 AVHRR with reference to ERS-1 SAR data: a case study in the Brazilian Amazon

Abstract Two coarse spatial resolution classifications of nominally 1·1 km resolution of deforested areas over a test site covering part of the south-west Amazon basin are compared. One classification is derived from data acquired by NOAA's Advanced Very High Resolution Radiometer (AVHRR) and the other from the ERS-1 Along Track Scanning Radiometer (ATSR-1). A forest/non-forest classification derived from finer spatial resolution ERS-1 Synthetic Aperture Radar (SAR) data is used as a reference for the comparison. Specific patterns of deforestation in the area are identified and their depiction on each of the coarse spatial resolution datasets is examined in relation to their depiction on the fine spatial resolution classification. The results show that significant differences exist between the two coarse spatial resolution classifications and that special rigorous integration methodologies will have to be developed before the results from either source can be used interchangeably with those from the other.

Mesoproterozoic tectonic correlations between eastern Laurentia and the western border of the Amazon Craton

A possible palaeogeographic link between the Grenville and Rondonia-Sunsas provinces is reinforced by the timing of thermometamorphic and plutonic events. Equivalent terms of regional geological time scales are: Ketilidian = Transamazonian; Palaeohelikian or Elsonian = Rondonian-San Ygnacio; Neohelikian or Grenvillian = Sunsas; Hadrynian = Brasiliano. Remobilization of the older crust is another feature common to both provinces in Helikian times. Felsic volcanics extruded 1650 million years ago in the eastern Grenville Province show 1.6 Ga analogues in the Roosevelt lava flows of the Amazon Craton. Also a recently defined 1470–1500 Ma Pinwarian event in the Grenville shows correlatives in the final stages of evolution of the Rio Negro-Juruena belt. Significant anorthosite-mangerite-charnokite-granite (AMCG) plutonism affected both regions during closely spaced periods of time. Two pulses of late potash-rich plutonism responsible for rapakivi intrusions from about 1.1 to 0.95 Ga are recognized in Grenvillia from Labrador to Texas and in the Rondonian-Sunsas Province of the Amazon Craton. Differences between the provinces include AMCG massifs of northeastern Laurentia whose equivalents in Rondonia are small layered mafic bodies, besides mangeritic/charnockitic intrusions and the large extensional and transtensional features of Sunsas age in the southwest Amazon sector. The AMCG plutonism roughly coeval with cratonic magmatism associated with transtensional features in the Amazon Craton allow two possible models to be postulated: (a) Amazonian transtensional features originated in response to collision with a left-lateral component, as along the Grenville front similar to the reactivation of the Asian continent due to the Himalayan push (diva basins and magmatism on the Sinian Platform); (b) major continental extensions related to the start of two Wilson cycles, one preceding the opening of a Grenvillian Ocean at around 1.4–1.3 Ga and, the other, due to the separation of Laurentia from Amazonia at the end of the Grenvillian cycle. Both have been related to extensive underplating.

Carbon Dioxide Uptake by an Undisturbed Tropical Rain Forest in Southwest Amazonia, 1992 to 1993

Measurements of carbon dioxide flux over undisturbed tropical rain forest in Brazil for 55 days in the wet and dry seasons of 1992 to 1993 show that this ecosystem is a net absorber of carbon dioxide. Photosynthetic gains of carbon dioxide exceeded respiratory losses irrespective of the season. These gains cannot be attributed to measurement error, nor to loss of carbon dioxide by drainage of cold air at night. A process-based model, fitted to the data, enabled estimation of the carbon absorbed by the ecosystem over the year as 8.5 ± 2.0 moles per square meter per year.

The malarial impact on the nutritional status of Amazonian adult subjects.

The anthropometric (body weight, height, upper arm circumference, triceps and subescapular skinfolds; Quetelet index and arm muscle circumference) and blood biochemistry (proteins and lipids) parameters were evaluated in 93 males and 27 females, 17-72 years old voluntaries living in the malarial endemic area of Humaita city (southwest Amazon). According to their malarial history they were assembled in four different groups: G1--controls without malarial history (n:30); G2--controls with malarial history but without actual manifestation of the disease (n:40); G3--patients with Plasmodium vivax (n:19) and G4--patients with Plasmodium falciparum (n:31). The malarial status was stablished by clinical and laboratory findings. The overall data of anthropometry and blood biochemistry discriminated the groups differently. The anthropometric data were low sensitive and contrasted only the two extremes (G1 > G4) whereas the biochemistry differentiated two big groups, the healthy (G1 + G2) and the patients (G3 + G4). The nutritional status of the P. falciparum patients was highly depressed for most of the studied indices but none was sensitive enough to differentiate this group from the P. vivax group (G3). On the other hand the two healthy groups could be differentiated through the levels of ceruloplasmin (G1 < G2) and alpha nitrogen (G1 > G2). Thus it seems that the malaria-malnourishment state exists and the results could be framed either as a consequence of nutrient sink and/or the infection stress both motivated by the parasite.

Mercury in the Madeira River ecosystem, Rondônia, Brazil

A survey of mercury levels in river water and sediments, forest soils, fish, air and human hair is presented for the Madeira River watershed in southwest Amazonia, Brazil. Mercury levels appeared particularly high in tributary rivers close to major gold-mining areas. High Hg levels in fish (up to 2.7 ppm) were also found in such areas. Atmospheric Hg levels were mostly close to background, but can reach high values (3.2 mg/m 3) in the proximity of the HgAu reburning complex. Human-hair levels, however, reach values up to 26.7 ppm, indicating high exposure rates of the local population.

A Note on Trophic Complexity and Community Stability

A Note on Trophic Complexity and Community Stability