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Search Results: 1 - 10 of 501791 matches for " Carlos A. Vettorazzi "
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Relative reduction in annual soil loss in micro watersheds due to the relief and forest cover
Mingoti, Rafael;Vettorazzi, Carlos A;
Engenharia Agrícola , 2011, DOI: 10.1590/S0100-69162011000600017
Abstract: with the intense debate, in brazil, between landowners and public agencies about the amount of area with forest cover needed in different regions, there is an increase of the need for provision of technical data used as a basis for decision making. one of the criteria to evaluate the effect of forest cover in protecting water resources is the soil loss, which leads to several consequences on the environment, including the silting of the rivers. therefore, this study aimed to evaluate the reduction in the soil loss in micro watersheds with different reliefs, size and location of forest cover, in the corumbataí river watershed, in the state of s?o paulo, using the revised universal soil loss equation (rusle) in a gis environment. for this study, 18 watersheds in three degrees of slope were selected, and 20 scenarios for land-use were established, by analyzing the influence of the ppa size, and the size and the location of the legal reserve. the results showed that: a) the effect of forest cover in reducing annual soil loss varies depending on the average slope of the watershed; b) the ppa width must be determined taking into account the slope of the watershed; c) the legal reserve must be located along the ppa. these provide better results in reducing annual soil loss.
Exatid?o de posicionamento de um receptor GPS, operando sob diferentes coberturas vegetais
Angulo Filho, Rubens;Vettorazzi, Carlos A.;Sarries, Gabriel A.;
Revista Brasileira de Engenharia Agrícola e Ambiental , 2002, DOI: 10.1590/S1415-43662002000200023
Abstract: to evaluate planimetric positioning accuracy of a gps receiver (trimble/pro-xl), operating under different conditions of vegetation cover (pasture, rubber trees, eucalyptus and pine trees), 6 control points were located randomly in the study area. for comparison, their coordinates were first obtained by a conventional surveying method, according to nbr 13133 of brazilian surveying standards. afterwards, the gps receiver was positioned on those control points, maintaining the acquisition rate of 1 s while changing the time for 1, 5 and 10 min, the dgps method was used to correct the positioning coordinate data. according to the methodology applied and the results obtained, it was possible to distinguish planimetric positioning accuracy, according to the vegetation cover, in two groups: with and without tree canopy, confirming its interference on the receiver signal reception emitted by the gps satellites. increasing the time with the receiver over the control points improved the planimetric positioning accuracy, which emphasizes the importance of appropriate choice of the surveying methodology to be utilized.
Rela??o entre índice de área foliar e fra??es de componentes puros do modelo linear de mistura espectral, usando imagens ETM+/Landsat
Xavier, Alexandre C.;Vettorazzi, Carlos A.;Machado, Ronalton E.;
Engenharia Agrícola , 2004, DOI: 10.1590/S0100-69162004000200022
Abstract: the leaf area index (lai) is one of the most important biophysical variable of the vegetation for modeling, and it is directly related to evapotranspiration, vegetation yield and rain interception. the aim of this paper was to analyze the relationship between lai and endmember fractions estimated by linear spectral mixture modelling (lsmm). the study area was a watershed, in piracicaba, state of s?o paulo, brazil. lai was measured with lai-2000 equipment in 32 samples in the field with different vegetation cover. the lsmm was applied to a landsat/etm+ image, corrected for the atmospheric effects by 6s model. three endmembers were considered in the lsmm: vegetation, soil, and shade. the relationship between all lais and vegetation and soil fractions (fvg and fso) were significant, although weak. the relationship between sugar-cane lai with fvg and with fso showed better fits. these results indicated that the vegetation type had influenced on the lsmm and that the stratification by vegetation physiognomy is suggested to improve the lai estimation. relationship between lai and shadow fraction was not statistically significant.
Uso de fotografias aéreas coloridas 35 mm na avalia??o de produtividade de gr?os
Araújo, Jo?o C. de;Molin, José P.;Vettorazzi, Carlos A.;
Engenharia Agrícola , 2004, DOI: 10.1590/S0100-69162004000300021
Abstract: precision agriculture is being used as an alternative for improving production in developed countries. in brazil it is just starting and research contribution is fundamental in the process of its adoption. this work aimed to study the potential use of 35 mm color aerial photos to predict yield in grain crops. some fields are been intensivelly monitored and data are been taken, like yield maps, physical and chemical soil properties, weeds, diseases and pests and also 35 mm color aerial photos. the photos were georeferenced by ground flags located with dgps. after selecting the best photos, they were scanned. the images and yield maps were processed and the regressions between images and yield were analized. low determination coefficients were obtained in all cases, showing little potential for this kind of information on predicting yield variability in the field.
Leaf area index of ground covers in a subtropical watershed
Xavier, Alexandre Candido;Vettorazzi, Carlos Alberto;
Scientia Agricola , 2003, DOI: 10.1590/S0103-90162003000300002
Abstract: leaf area index (lai), an important structural variable descriptive of vegetation, is directly related to evapotranspiration and productivity. the objective of this work was to measure and analyze monthly lai of different ground covers in a subtropical watershed. a field campaign to collect monthly lai data was carried out during the year 2001, with a lai-2000 (plant canopy analyzer) device, in sugarcane, pasture, corn, eucalypt, and riparian forest patches. riparian forest presented a maximum lai of 4.90; lai values decreased as precipitation decreased, as it is a characteristic of this type of semideciduous vegetation. lai for sugar cane presented the greatest variability throughout the year, related to plant characteristics and crop management in the study area. results represent an initial step for the understanding of lai dynamics in the study area and areas under similar conditions.
Monitoring leaf area index at watershed level through NDVI from Landsat-7/ETM+ data
Xavier, Alexandre Candido;Vettorazzi, Carlos Alberto;
Scientia Agricola , 2004, DOI: 10.1590/S0103-90162004000300001
Abstract: leaf area index (lai) is an important parameter of the vegetation canopy, and is used, for instance, to estimate evapotranspiration, an important component of the hydrological cycle. this work analyzed the relationship between lai, measured in field, and ndvi from four dates (derived from landsat-7/etm+ data), and with such vegetation index, to generate and analyze lai maps of the study area for the diverse dates. lai data were collected monthly in the field with lai-2000 equipment in stands of sugar cane, pasture, corn, eucalypt, and riparian forest. the relationships between lai and ndvi were adjusted by a potential model; 57% to 72% of the ndvi variance were explained by the lai. lai maps generated by empirical relationships between lai and ndvi showed reasonable precision (standard error of lai estimate ranged from 0.42 to 0.87 m2 m-2). the mean lai value of each monthly lai map was shown to be related to the total precipitation in the three previous months.
Leaf area index of ground covers in a subtropical watershed
Xavier Alexandre Candido,Vettorazzi Carlos Alberto
Scientia Agricola , 2003,
Abstract: Leaf Area Index (LAI), an important structural variable descriptive of vegetation, is directly related to evapotranspiration and productivity. The objective of this work was to measure and analyze monthly LAI of different ground covers in a subtropical watershed. A field campaign to collect monthly LAI data was carried out during the year 2001, with a LAI-2000 (plant canopy analyzer) device, in sugarcane, pasture, corn, eucalypt, and riparian forest patches. Riparian forest presented a maximum LAI of 4.90; LAI values decreased as precipitation decreased, as it is a characteristic of this type of semideciduous vegetation. LAI for sugar cane presented the greatest variability throughout the year, related to plant characteristics and crop management in the study area. Results represent an initial step for the understanding of LAI dynamics in the study area and areas under similar conditions.
Monitoring leaf area index at watershed level through NDVI from Landsat-7/ETM+ data
Xavier Alexandre Candido,Vettorazzi Carlos Alberto
Scientia Agricola , 2004,
Abstract: Leaf area index (LAI) is an important parameter of the vegetation canopy, and is used, for instance, to estimate evapotranspiration, an important component of the hydrological cycle. This work analyzed the relationship between LAI, measured in field, and NDVI from four dates (derived from Landsat-7/ETM+ data), and with such vegetation index, to generate and analyze LAI maps of the study area for the diverse dates. LAI data were collected monthly in the field with LAI-2000 equipment in stands of sugar cane, pasture, corn, eucalypt, and riparian forest. The relationships between LAI and NDVI were adjusted by a potential model; 57% to 72% of the NDVI variance were explained by the LAI. LAI maps generated by empirical relationships between LAI and NDVI showed reasonable precision (standard error of LAI estimate ranged from 0.42 to 0.87 m2 m-2). The mean LAI value of each monthly LAI map was shown to be related to the total precipitation in the three previous months.
Chironomidae (Insecta, Diptera) from Alto Paranapanema Basin, southeastern Brazil
Kathia Sonoda,Juaci Malaquias,Carlos Vettorazzi
Chironomus Newsletter on Chironomidae Research , 2010,
Abstract: We investigated the community of Chironomidae from three rivers belonging to the same river basin in Southern Brazil. Our objective was to analyze if the Chironomidae communities from rivers of the same basin were similar and relate this to land-use and water quality variables. Samples of insects were taken using artificial substrate baskets and left 44 days in the field for colonization during the dry season in 2002. Study reaches with the relevant land-use category present for at least 500 m along both river banks above and alongside the study reach were selected and land-use, terrain slope of the river basin and chemical and physical variables of the water were analysed. Faunal data were analyzed by number of individuals, richness of genera and community indices. Statistical analyses were performed in order to investigate the relationship between abiotic variables and the Chironomidae communities. Twenty-two genera were identified; Rheotanytarsus (Thienemann & Bause) was the most abundant in all assemblages. Some genera showed preferences in their distribution, and were observed in only one of the rivers. Land-use and slope of the terrain were similar for all rivers, while the water quality variables were different for the Taquari River compared to the two other sites. This may explain the differences in the Chironomidae community observed for this locality
Caracteriza??o de solos do Vale do Ribeira de Iguape no Estado de S?o Paulo através de índices de relevo
Vettorazzi, C.A.;Angulo Filho, R.;
Anais da Escola Superior de Agricultura Luiz de Queiroz , 1986, DOI: 10.1590/S0071-12761986000200009
Abstract: through relief indices obtained from circular samples on a planialtimetric chart (1:35,000), the characterization was made of five soil units occurring in the ribeira de iguape valley in the s?o paulo state and the efficiency of the indices in the discrimination between these soils was also tested. the relief indices utilized in this study were mean declivity, maximum altimetric amplitude and mean length of the slopes. the five soils studied were: a) alic yellow lato sol - laa (pariqüera unit); b) alic latosolic red-yellow podzolic - pvla-1 (taquaru?u unit); c) alic latosolic red-yellow podzolic - pvla-2 (arataca unit); d) alic red-yellow podzolic-pva (vapamirim unit); e) alic cambisol - ca-2 (canfilito unit). the relief indices made possible the characterization and discrimination of the studied soils, and the most efficient indices for differentiating the five soil units were maximum altimetric amplitude and mean declivity.
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