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  • 1
    Electronic Resource
    Electronic Resource
    SPATIAL AND TEMPORAL WATER QUALITY VARIABILITY IN THE PIRACICABA RIVER BASIN, BRAZIL (1997)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of the American Water Resources Association 33 (1997), S. 0 
    Details
    ISSN: 1752-1688
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Architecture, Civil Engineering, Surveying , Geography
    Notes: : The spatial and temporal variability of dissolved oxygen (DO), biochemical oxygen demand (BOD), nitrate concentration and total coliform (TC) were investigated at nine sampling stations distributed along the main rivers of the Piracicaba River Basin, a 12,400 km2 catchment located in São Paulo State, one of the most developed regions of Brazil. Spatially, a downstream impoverishment of water quality conditions was observed, as seen by the decrease of DO, and increase of BOD, nitrate, and TC. These changes were probably caused by accumulating downstream discharge of domestic and industrial sewage. Temporal evaluation of 18 years of data showed that DO decreased with time for the majority of the sampling stations, while BOD, nitrate, and TC increased. A law, approved at the end of 1991, proposed a new water tax for river water extraction for industrial and agricultural use. The amount of this tax is determined according to the water quality of the extracted water. Therefore, the evaluation of the water quality status in this basin is a first step to help resources managers to determine the values for this tax.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1752-1688.1997.tb04129.x
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  • 2
    Electronic Resource
    Electronic Resource
    CO2 flux from soil in pastures and forests in southwestern Amazonia (2004)
    Oxford, UK : Blackwell Science Ltd
    Global change biology 10 (2004), S. 0 
    Details
    ISSN: 1365-2486
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Energy, Environment Protection, Nuclear Power Engineering , Geography
    Notes: Stocks of carbon in Amazonian forest biomass and soils have received considerable research attention because of their potential as sources and sinks of atmospheric CO2. Fluxes of CO2 from soil to the atmosphere, on the other hand, have not been addressed comprehensively in regard to temporal and spatial variations and to land cover change, and have been measured directly only in a few locations in Amazonia. Considerable variation exists across the Amazon Basin in soil properties, climate, and management practices in forests and cattle pastures that might affect soil CO2 fluxes. Here we report soil CO2 fluxes from an area of rapid deforestation in the southwestern Amazonian state of Acre. Specifically we addressed (1) the seasonal variation of soil CO2 fluxes, soil moisture, and soil temperature; (2) the effects of land cover (pastures, mature, and secondary forests) on these fluxes; (3) annual estimates of soil respiration; and (4) the relative contributions of grass-derived and forest-derived C as indicated by δ13CO2. Fluxes were greatest during the wet season and declined during the dry season in all land covers. Soil respiration was significantly correlated with soil water-filled pore space but not correlated with temperature. Annual fluxes were higher in pastures compared with mature and secondary forests, and some of the pastures also had higher soil C stocks. The δ13C of CO2 respired in pasture soils showed that high respiration rates in pastures were derived almost entirely from grass root respiration and decomposition of grass residues. These results indicate that the pastures are very productive and that the larger flux of C cycling through pasture soils compared with forest soils is probably due to greater allocation of C belowground. Secondary forests had soil respiration rates similar to mature forests, and there was no correlation between soil respiration and either forest age or forest biomass. Hence, belowground allocation of C does not appear to be directly related to the stature of vegetation in this region. Variation in seasonal and annual rates of soil respiration of these forests and pastures is more indicative of flux of C through the soil rather than major net changes in ecosystem C stocks.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1529-8817.2003.00776.x
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  • 3
    Electronic Resource
    Electronic Resource
    Stable isotope analysis of energy sources for larvae of eight fish species from the Amazon floodplain (2002)
    Oxford, UK : Blackwell Science, Ltd
    Ecology of freshwater fish 11 (2002), S. 0 
    Details
    ISSN: 1600-0633
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract – Aquatic macrophytes form the most productive habitat of the Amazon floodplain and account for more than 60% of the net primary production of the ecosystem. Aquatic grasses are the dominant macrophytes and the main feeding ground of Amazonian larval fish. The present study used stable isotopes of nitrogen and carbon to measure the contribution of aquatic grasses to the production of eight larval fish, and describes the structure of the trophic chain. The carnivore larvae were at the third trophic level, and the detritivores were at the second and third trophic levels. The contribution of aquatic grasses to larval fish production was variable. It could reach a mean value of 25% for three species, but its contribution probably did not exceed 12% in the other five species.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1034/j.1600-0633.2002.110106.x
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  • 4
    Electronic Resource
    Electronic Resource
    Stable carbon isotope ratio of tree leaves, boles and fine litter in a tropical forest in Rondônia, Brazil (1998)
    Springer
    Oecologia 114 (1998), S. 170-179 
    Details
    ISSN: 1432-1939
    Keywords: Key words Amazon ; Vegetation ; Forest ; Stable carbon isotope ; Rondônia
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Leaves of 208 trees were collected for isotopic analysis together with wood from 36 tree boles and 18 samples of fine litter from a terra-firme forest located at Samuel Ecological Reserve, Rondônia State, in the southwestern Amazon region. The range of δ13C values in leaves was from −28 to −36‰, with an average (±1 SD) of −32.1 ± 1.5‰, which was more negative than the δ13C values of bole samples (−28.4 ± 2.0‰) and fine litter (−28.7 ± 2.0‰). These values are within the range found for tropical and subtropical forests. Pooling the δ13C values for leaf samples from trees of the same height gave averages which were positively correlated with plant height at a highly significant level, with a slope of 0.06 and an intercept of −33.3‰ and a correlation coefficient r 2=0.70 (P〈0.001).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004420050433
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  • 5
    Electronic Resource
    Electronic Resource
    Carbon-13 variation with depth in soils of Brazil and climate change during the Quaternary (1996)
    Springer
    Oecologia 106 (1996), S. 376-381 
    Details
    ISSN: 1432-1939
    Keywords: Amazon ; Vegetation change ; Stable carbon isotope ; Radiocarbon ; Soil organic matter
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Paleoecological and geomorphological studies indicate that, during the middle Holocene, there was a predominance of drier conditions with grassy savannahs replacing forests across the South American continent. Modern savannahs are composed mainly of C4 plants and soils developed under this type of vegetation show enrichment in 13C compared to soils under C3 vegetation cover. If soils contain stabilized organic matter formed in the middle Holocene, we hypothesize that former C4 vegetation would be evidenced by a large enrichment of 13C in soil organic matter (SOM). We investigate this possibility examining the depth variation of carbon isotopic composition in 21 soil profiles collected by different researchers at 14 different sites in Brazil. Of these, profiles from only three sites showed a marked increase of 13C with depth (9–10‰ enrichment in δ13C difference between the surface soil and deepest depth); two sites showed intermediate enrichment (4–5‰), and nine sites showed a small enrichment of approximatelly 2.5‰. The majority of sites showing all-C3 derived SOM were in the Amazon region. Possible causes for the absence of a large 13C enrichment with depth are: (1) dominance of C3 rather than C4 grasses in mid-Holocene savannahas, (2) soil profiles did not preserve organic matter derived from mid-Holocene plants, (3) the retreat of forest areas did not occur on a regional scale, but was a much more localized phenomenon.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00334565
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  • 6
    Electronic Resource
    Electronic Resource
    15N natural abundance in plants of the Amazon River floodplain and potential atmospheric N2 fixation (1992)
    Springer
    Oecologia 90 (1992), S. 591-596 
    Details
    ISSN: 1432-1939
    Keywords: 15N ; Atmospheric nitrogen fixation ; Floodplain ; Amazon river
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The15N natural abundance values of various Amazon floodplain (várzea) plants was investigated. Samples of young leaf tissues were collected during three different periods of the river hydrography (low water, mid rising water and high water) and during one period in the Madeira River (high water). A large variation of15N abundance was observed, both among the different plant types and between the different flood stages. This variation probably, reflected, in part, the highly variable nature of the floodplain, sometimes dry and oxygenated and at other times inundated and anaerobic and, in part, changes in plant nitrogen metabolism. Comparison of the nitrogen isotopic composition of leguminous plants with that of non-leguminous plants showed that, on average, the15N abundance was lower in the legumes than non-legumes, suggesting active N-fixation. Also, the15N natural abundance in aquatic grasses of the generaPaspalum, was in general, lower than the15N abundance of aquatic grasses of the generaEchinochloa. As both of these grasses grow in the same general habitat, it appears thatPaspalum grasses may also be nitrogen fixers.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01875455
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  • 7
    Electronic Resource
    Electronic Resource
    Biogeochemistry of the Madeira river basin (1989)
    Springer
    GeoJournal 19 (1989), S. 391-397 
    Details
    ISSN: 1572-9893
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geography
    Notes: Abstract A biogeochemical characterization of the Madeira river basin has been made to evaluate the local and global effects of possible alterations in the ecosystem caused by recent intensive occupation in Rondonia state. During the period April 1983—January 1986, sampling was made both by land and river along the tributaries and main channel of the Madeira river. The parameters analysed lead to a detailed study of the physicochemical quality of the waters of the basin and their relationship with the local geology, associated with the transport of solid material and the hydrological behavior of the ecosystem. Penman's method adapted to tropical rainforest conditions was used to evaluate the potential evapotranspiration for the basin. Estimated potential evapotranspiration was 1420 mm/y, 77% due to the energy balance. Real evapotranspiration was 94% of the estimated potential and the main residence time of the rain water in the basin was 2 months. The isotopic behavior of Hydrogen and Oxygen in the river waters of the region was typical of great rivers, the values being more positive during the dry season and more negative during the rainy season. An isotopic gradient of δ 18O 0.038 (‰)/100 km, was established from Porto Velho station to the estuary, which was considered low when compared with the value of 0.063 (‰)/100 km, obtained for the Amazon river. In general, the waters of the tributaries were poor in dissolved ion species when compared with the main channel of the Madeira river. Seasonal variation in the transport of suspended sediment kept the same pattern, greater transport being observed on rising water than during high water. A transport of 2.85 million tons per day was observed in the Madeira river near the mouth.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00176908
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  • 8
    Electronic Resource
    Electronic Resource
    The response of field grownPhaseolus vulgaris to Rhizobium inoculation and the quantification of N2 fixation using15N (1985)
    Springer
    Plant and soil 88 (1985), S. 333-343 
    Details
    ISSN: 1573-5036
    Keywords: Acetylene reduction ; Bean cultivars ; Harvest index ; 15N dilution ; Nitrogen fixation ; Nodulation ; Phaseolus vulgaris ; Rhizobium inoculation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary A field experiment was performed to assess the effects of Rhizobium inoculation and nitrogen fertilizer (100 kg N ha−1) on four cultivars of Phaseolus beans; Carioca, Negro Argel, Venezuela 350 and Rio Tibagi. In the inoculated treatment 2.5 kg N ha−1 of15N labelled fertilizer was added in order to apply the isotope dilution technique to quantify the contribution of N2 fixation to the nutrition of these cultivars. Nodulation of all cultivars in the uninoculated treatments was poor, but the cultivars Carioca and Negro Argel were well nodulated when inoculated. Even when inoculated, nodulation of the cultivars Venezuela 350 and Rio Tibagi was poor and these cultivars showed little response to inoculation in terms of nitrogen accumulation or grain yield. The estimates of the contribution of N2 fixation estimated using the isotope dilution technique, for the Carioca and Negro Argel cultivars, amounted to 31.7 and 18.4 kg N ha−1 respectively. These two cultivars produced 991 and 883 kg ha−1 of grain, respectively, when inoculated and 663 and 620 kg ha−1 with the addition of 100 kg N ha−1 of N fertilizer. The response to nitrogen was particularly poor due to high leaching losses in the very sandy soil at the experimental site. The Venezuela 350 and Rio Tibagi cultivars only responded to N fertilizer and not to inoculation with Rhizobium which stresses the great importance of selecting plant cultivars for nitrogen fixation in the field.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02197490
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  • 9
    Electronic Resource
    Electronic Resource
    Estimation of biological nitrogen fixation associated withBrachiaria andPaspalum grasses using15N labelled organic matter and fertilizer (1986)
    Springer
    Plant and soil 90 (1986), S. 265-292 
    Details
    ISSN: 1573-5036
    Keywords: Brachiaria spp ; Nitrogen fixation ; 15N techniques ; Paspalum notatum ; Pasture grasses
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Six pasture grasses,Paspalum notatum cv batatais,P. notatum cv pensacola,Brachiaria radicans, B. ruziziensis, B. decumbens andB. humidicola, were grown in concrete cylinders (60 cm diameter) in the field for 31 months. The soil was amended with either a single addition of15N labelled organic matter or frequent small (2 kg N. ha−1) additions of15N enriched (NH4)2SO4. In the labelled fertilizer treatment soil analysis revealed that there was a very drastic change in15N enrichment in plant-available nitrogen (NO 3 − +NH 4 + ) with depth. The different grass cultivars recovered different quantities of applied labelled N, and evidence was obtained to suggest that the roots exploited the soil to different depths thus obtaining different15N enrichments in soil derived N. This invalidated the application of the isotope dilution technique to estimate the contribution of nitrogen fixation to the grass cultivars in this treatment. In the labelled organic matter treatment the15N label in the plant-available N declined at a decreasing rate during the experiment until in the last 12 months the decrease was only from 0.274 to 0.222 atom % excess. There was little change in15N enrichment of available N with depth, hence it was concluded that although the grasses recovered different quantities of labelled N, they all obtained virtually the same15N enrichment in soil derived N. Data from the final harvests of this treatment indicated thatB. humidicola andB. decumbens obtained 30 and 40% respectively of their nitrogen from N2 fixation amounting to an input of 30 and 45 kg N.ha−1 year−1 respectively.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02277403
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  • 10
    Electronic Resource
    Electronic Resource
    Estimation of N2-fixation by sugarcane,Saccharum sp., and soybean,Glycine max, grown in soil with15N-labelled organic matter (1984)
    Springer
    Plant and soil 82 (1984), S. 257-261 
    Details
    ISSN: 1573-5036
    Keywords: Glycine max ; Isotope dilution technique ; Nitrogen-15 ; Nitrogen-fixation ; Organic matter ; Substrate-labelling ; Saccharum sp. ; Soybean ; Sugarcane
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Two varieties of sugarcane, and nodulated and non-nodulated soybean isolines, were planted in a soil previously mixed with15N-labelled plant material. 45 days was allowed to elapse before planting, to permit initiation of organic matter mineralization. Plants were grown for 60 days, then harvested, dried, weighed and analysed for total N. Analysis of soil samples pre-incubated in the laboratory was carried out to evaluate ammonium and nitrate from added organic matter. Dry weights of the soybean isolines were similar, but total N was higher for the nodulated line. Both sugarcane varieties showed similar weight and total N. Nitrogen derived from applied organic matter (NdfOM) was higher in non-nodulated soybean than in all other plants. Although there is the possibility of different15N availabilities between species, nitrogen derived from fixation (Nfix) was calculated based on the15N enrichment of the non-nodulating soybean. Nfix was 72% for nodulating soybean and ranged from 19 to 39% for different parts of sugarcane plants, despite high levels of available-N. Nitrogen derived from soil was calculated by difference. NdfOM was lower in roots than in upper parts (leaves+stalks) of plants. Use of15N labelled organic matter seems a useful approach to the longer term measurement of N2-fixation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02220252
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