Changes of chemical properties in an oxisol after clearing of native Cerrado vegetation for agricultural use in Vilhena, Rondonia State, Brazil     

J.L.N. Carvalho  C.E.P. Cerri  C.C. Cerri  B.J. Feigl  M.C. Píccolo  V.P. Godinho  U. Herpin 《Soil & Tillage Research》2007,96(1-2):95-102

Native vegetation clearing in the Amazon Cerrado region for agricultural purposes may be modifying soil chemical characteristics. The extent of change depends on the management practices used. We evaluated changes in chemical properties of a clayey oxisol (dystrophic red yellow latosol) under no-tillage (NT) and conventional tillage (CT). Soil samples were taken randomly (n = 5) in July 2004 at 0–5 cm, 5–10 cm, 10–20 cm and 20–30 cm depths at six treatments: Cerrado with native vegetation, CT cultivated with rice for 1 year (1CT) and 2 years (2CT), and NT cultivated with soybean for 1 year (1NT), 2 years (2NT) and 3 years (3NT) in each case after a 2-year period of rice under CT. Soil pH (CaCl₂, KCl and water), ΔpH, total acidity (H⁺ + Al³⁺), total organic carbon (TOC), available P, exchangeable K, Ca, Mg, potential cation exchange capacity (CEC) and base saturation (V) were determined. The highest pH values were determined in topsoil layers at the older NT adoption. Under Cerrado pH was lower than under cultivation at all depths due to absence of lime application. Generally, negative values of ΔpH were observed at all sites in all layers indicating predominant presence of negative charges in the soil. Although not statistically significant it seems that the amount of negative charges was higher in deeper layers. Total acidity displayed the highest values throughout the soil profile under Cerrado and low pH and low concentrations of exchangeable bases. Cultivated systems with fertilizer generated considerable increases of P, K, Ca, and Mg compared to Cerrado. Soil macronutrient content and base saturation under NT gradually increased throughout the profile with time. Highest CEC values were calculated for the 0–5 cm and 5–10 cm layers under Cerrado and NT systems. For the 0–5 cm layer CEC was lower at the CT system compared to the Cerrado and the oldest year under NT system.

Alteration of TOC was more pronounced in the top 10 cm layer at all sites. The highest content was measured in the topsoil layer under Cerrado. Considering the future land use in Cerrado areas the NT system, if properly managed, appears to be the favourable management option of the existing croplands established after Cerrado clearing.  相似文献   

Indian land use in the Raposa–Serra do Sol Reserve,Roraima, Amazonia,Brazil: Physical and chemical attributes of a soil catena developed from mafic rocks under shifting cultivation     

Valdinar F. Melo  Carlos Ernesto G.R. Schaefer  Sandra Cátia P. Uchôa 《CATENA》2010

Native Indians (Macuxi, Ingarikó and Uapishana) in the Raposa–Serra do Sol Indian Reserve have been cultivating forest soils since the early XIX century, especially those derived from dolerite sills, scattered within the quartzitic dominated landscape. Representative soils developed from mafic rocks under Indian shifting cultivation in northeastern Roraima, were submitted to physical, chemical and mineralogical analyses to characterize their pedogenetic characteristics and infer on their status under native Indian shifting cultivation. The soil profiles were classified as: Orthic Ebanic Chernosol (USDA Mollisol), vertic Orthic Ebanic Chernosol (USDA Mollisol), Eutrophic Haplic Cambisol (USDA mollic Inceptisol) and Eutrophic Red Nitosol (USDA Red Alfisol), which occupy, respectively, lower slopes and less dissected terrains (Mollisols) and steeper slopes (Alfisols). The first two are eutrophic, and not typical of the Amazon region. Their mineralogies range from kaolinite/goethite rich upland, deeply weathered Nitosol, to 2:1 clay rich downslope Chernosols. The latter has primary minerals in the silt fraction and high CEC resulting in high fertility. The Nitosols reveal a process of severe topsoil loss, due to widespread sheet erosion from deforestation and shifting cultivation. Chemical analyses showed varied soil fertility, ranging from high levels in the Chernosols to a low level in the non-cultivated Nitosol. Phosphorus levels are limited in all soils, despite the high fertility. The Chernosols located in lowland, flat areas close to the valley floor are more suitable environments for the slash-and-burn native farming system. In the Chernosols and Cambisols, the clay activity below the value limit for this class indicates a current natural process of increasing leaching. The more weathered and eroded Nitosol showed low Fe-oxalate and Si-oxalate levels. Micronutrients such as total zinc and copper, decreased with depth and weathering. The Nitosols showed the highest phosphate adsorption levels (1.574 mg g^− 1 of soil) which can be attributed to its clayey texture. Chernosols showed overall lower P adsorption values, increasing with depth. All soils under native Indian cultivation display signs of physical and chemical degradation due to shortened fallow under intense land use pressure in the Raposa–Serra do Sol Reserve.  相似文献   

Gastric coccidiosis in Thoracocharax stellatus caused by Goussia guamaensis n. sp. (Apicomplexa: Eimeriidae) from the Amazon region     

Marcelo F. da Silva  Rebeca S. de Araújo  Diehgo T. da Silva  Osimar Sanches  Igor Hamoy  Edilson Matos 《Journal of fish diseases》2019,42(6):905-912

Ninety‐seven specimens of spotfin hatchetfish, Thoracocharax stellatus, an ornamental freshwater species from the Amazon basin, were captured in the basin of the Guamá River in the municipality of Belém, in northern Brazil, and analysed for coccidiosis infection. Overall, 26 of the specimens were infected by apicomplexan parasites of the genus Goussia, with unsporulated forms being found in the gastric epithelium and sporulated forms in the intestinal lumen. The spheroid oocysts (mean diameter: 13.2 ± 1.7 μm) have four elliptical sporocysts. A partial sequence of the SSU rDNA of the new species was obtained, which contained 1,121 base pairs, with 43.8% guanine + cytosine (G + C), and the bases distributed as follows: A = 28.1%, C = 18.3%, G = 25.5% and T = 28.1%. The combined analysis of the morphometric and phylogenetic evidence confirmed that the specimens represented the genus Goussia and were allocated to a new species, Goussia guamaensis n. sp., which is described here.  相似文献   

Feed management and stocking density of the endangered wild zebra pleco: Implications for captive breeding     

Fabrício Menezes Ramos  Higo Andrade Abe  Carlos Alberto Martins Cordeiro  Luis Andr Luz Barbas  Paulo Csar Falanghe Carneiro  Alexandre Nizio Maria  Rodrigo Yudi Fujimoto 《Aquaculture Research》2019,50(9):2437-2443

Due to the economic potential of Hypancistrus zebra in the ornamental fish market and its current classification as an endangered species in its natural occurrence sites, the present study sought to determine a suitable feed management strategy and stocking density to allow for an adequate captivity maintenance of this fish species. Three experiments were conducted as follows: (1) feed preference (artemia Artemia sp., shrimp Litopenaeus vannamei, fish Cynoscion spp. or mussel Perna perna); (2) determination of feeding rate (5% and 10% live weight day^?1) and frequency (1, 2 or 3 meals. Day^?1); and (3) evaluation of stocking density (0.25, 0.50, 1.00 and 2.00 g/L). Zebra pleco did not present the characteristic buccal scraping behaviour on the feed, commonly seen in other Loricariids. Artemia was the preferred diet followed by fish, shrimp and mussels. The frequency of two daily meals and the feeding rate of 10% live weight day^?1 allowed for an improved zootechnical performance. Zebra pleco showed enhanced specific growth rate at the density of 2 g/L. Our results suggest that, to improve the zebra pleco rearing conditions, it should be maintained at a density of 2 g/L, fed two daily meals at a feeding rate of 10% live weight day^?1. These findings correspond to useful information for an adequate management of this species and could assist in the supply of healthy specimens to the ornamental fish market as well for the restocking of declining wild populations.  相似文献   

Effect of seasonality and trophic group on energy acquisition in Amazonian fish     

R. Neves dos Santos  E. J. G. Ferreira  S. Amadio 《Ecology of Freshwater Fish》2008,17(2):340-348

Abstract –  The influence of hydrologic cycle and trophic groups on the energy content of food was investigated for five fish species from a Central Amazonian floodplain area. Sampling was carried out monthly using gillnets of different mesh sizes immersed in water for 24 h. We examined the presence and absence of food in fish stomachs and those with food were analysed and their energy content determined. Amongst the trophic groups studied, the piscivores Acestrorhynchus falcirostris and Pygocentrus nattereri showed high numbers of empty stomachs throughout the sampling period and very high levels of energy density in their food, which may explain why they take food less frequently. On the other hand the invertivorous species Hemiodus sp. and Hoplosternum littorale and the herbivore Rhytiodus microlepis , need to take food very frequently. The energy of the piscivorous species' stomach contents was not significantly different during the hydrologic cycle, whereas the invertivore and herbivore varied significantly, showing a general tendency of high levels of energy during high waters.  相似文献   

松梢枯病防治技术的研究   总被引：8，自引：1，他引：8       下载免费PDF全文

沈伯葵  姚景德  张明海  薛梦澜  姚长林 《林业科学研究》1993,6(4):409-413

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Production and harvest of fibers from Aphandra natalia (Palmae) in Ecuador     

Henrik Borgtoft Pedersen 《Forest Ecology and Management》1996,80(1-3):155-161

Aphandra natalia (Balslev & Henderson) Barfod is native to the western Amazon. It is exploited commercially for its leaf sheath and petiole fibers, which are used for brooms. Data from a 2 year study on production and harvest of fibers in the province of Morona-Santiago in Ecuador shows correlations to exist between the degree of the palm's exposure to light and leaf production, and between exposure to light and petiole length (maximum fiber length), while correlation is absent between exposure to light and fiber load per leaf. A linear relation was found between time and leaf production, with an overall average of 5.5 leaves produced per palm per year. No difference in leaf production of male and female palms was found among palms growing at low light intensities, while among palms in open, light-exposed areas, males were found to produce significantly more leaves than females. An average of 8.5 leaves are cut per palm per harvest, yielding 3.4 kg of fibers, while 6.9 leaves are left untouched. Average harvest time per palm is 33 min. Under optimal conditions (high densities of easy accessible palms), one harvester may harvest and clean about 20 kg of fibers in 1 day, selling at US$1.1 kg⁻¹. One hectare with high, but natural, densities of the palm may produce fibers worth US$460 per year, which can be harvested and prepared in 22 work days. Exploitation of the edible fruits may be combined with fiber extraction if female palms are left to produce fruits, while male palms are exploited for fibers, or if harvest frequency of fibers from female palms is lowered considerably below the average of once every 1.55 years. The exploitation practised in the study area appears sustainable.  相似文献   

Stable isotope analysis of energy sources for larvae of eight fish species from the Amazon floodplain     

R. G. Leite  C. A. R. M. Araújo-Lima  R. L. Victoria  L. A. Martinelli 《Ecology of Freshwater Fish》2002,11(1):56-63

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.  相似文献   

Abundance, body size and movement patterns of a tropical treefrog in continuous and fragmented forests in the Brazilian Amazon     

Selvino Neckel-Oliveira  Claude Gascon 《Biological conservation》2006,128(3):308-315

Phyllomedusa tarsius is a hylid frog that breeds in ponds located in a range of habitats from continuous forests to severely disturbed matrix habitats in Central Amazon. During three reproductive seasons, we followed the movement patterns, measured body size and registered abundance and residency time of this species in five habitats: pasture, Vismia regrowth, Cecropia regrowth, 1 and 10 ha forest fragments, and continuous forest. The frog captures were strongly correlated with rainfall in all disturbed habitats, but not in continuous forest, probably because individuals respond more directly to rainfall patterns in more open habitats. Males in disturbed habitats were smaller than those found in continuous forest, perhaps as a result of differences in habitat quality. Males remained at sites for longer periods in fragments and continuous forest compared to matrix habitats. Here again, the quality and suitability of breeding sites in matrix habitats may be lower than in continuous forest resulting in the need for more movement. We found bigger subpopulations in matrix habitat ponds and a higher percentage of individuals moving among them when compared to continuous forest ponds. Constant movement of individuals among disturbed subpopulations decreases population isolation and increases interbreeding among different subpopulations. No movement between individuals from continuous forest ponds and disturbed habitats was observed. This suggests that the disturbed habitat subpopulations are not acting as sink subpopulations for continuous forest populations. The maintenance of individuals in fragments is more dependent on local conditions for reproduction and on subpopulations in the matrix habitat than on recruitment of individuals from populations in continuous forest.  相似文献   

Effect of Harvest of Old Growth Douglas-fir Stands and Subsequent Management on Carbon Dioxide Levels in the Atmosphere     

《Journal of Sustainable Forestry》2013,32(1):61-77

A simple stand model is developed to assess the influence of management activities in old growth Douglas-fir forests on atmospheric CO, levels. Two natural disturbance regimes (450- and 240-year stand replacement fire cycles) are compared with four management regimes (45, 6 5 , 90-year plantation rotations, and conversion to non-forest use). Conversion of old growth Douglas-fir stands to plantations may actually decrease atmospheric C 4 for the fist few decades, but then increase it. The short term and long term changes are negligible compared to the atmospheric C02 produced by burning fossil fuels. Using wood as a substitute product for other materials (brick, aluminum, and plastic) dramatically reduces CO, released to the atmosphere; however, where wood is used as a luxury product, large quantities of C02 are released to the atmosphere under harvest regimes.  相似文献