Object-oriented and pixel-based classification approaches to classify tropical successional stages using airborne high–spatial resolution images     

Gustavo Antonio Piazza  Alexander Christian Vibrans  Veraldo Liesenberg  Júlio Cesar Refosco 《地理信息系统科学与遥感》2016,53(2):206-226

Airborne high–spatial resolution images were evaluated for mapping purposes in a complex Atlantic rainforest environment in southern Brazil. Two study sites, covered predominantly by secondary evergreen rainforest, were surveyed by airborne multispectral high-resolution imagery. These aerophotogrammetric images were acquired at four spectral bands (visible to near-infrared) with spatial resolution of 0.39 m. We evaluated different data input scenarios to suit the object-oriented classification approach. In addition to the four spectral bands, auxiliary products such as band ratios and digital elevation models were considered. Comparisons with traditional pixel-based classifiers were also performed. The results showed that the object-based classification approach yielded a better overall accuracy, ranging from 89% to 91%, than the pixel-based classifications, which ranged from 62% to 63%. The individual classification accuracy of forest-related classes, such as young successional forest stages, benefits the object-based approach. These classes have been reported in the literature as the most difficult to map in tropical environments. The results confirm the potential of object-based classification for mapping procedures and discrimination of successional forest stages and other related land use and land cover classes in complex Atlantic rainforest environments. The methodology is suggested for further SAAPI acquisitions in order to monitor such endangered environment as well as to support National Land and Environmental Management Protocols.  相似文献   

Species richness of the genus Molgolaimus (Nematoda) from local to ocean scale along continental slopes     

Gustavo Fonseca  Agnes W. Muthumbi  & Ann Vanreusel 《Marine Ecology》2007,28(4):446-459

This study investigated the distribution of Molgolaimus species (Nematoda) at different hierarchical spatial scales and observed the turnover of species along bathymetrical transects and among transects in two separate geographical regions. Samples from six transects (200–2000 m) from the Southern Oceans (SO) and four bathymetric transects (50–2000 m) from the Western Indian Ocean (WIO) were compared. Of the 30 species recorded, only one was common to both regions. WIO had higher local species richness than the SO. In both regions, the local scale was the greatest contributor to the total species richness. In the SO, there was no difference between species turnover at the different spatial scales, however, in the WIO, the turnover along bathymetrical transects was higher than among separated transects. For the particular genus studied, the evidence suggests that the study area in WIO has more widespread species and was better sampled, while the SO has many restricted species and it is most probably characterized by different biogeographical provinces. At the ocean scale (i.e. WIO versus SO), evolutionary histories may have strongly influenced nematodes species composition, while at local and regional scales, ecological processes are probably promoting species co‐existence and speciation. The high co‐existence of certain species at local scale is partially explained by species preference for different sediment layers.  相似文献   

Tintinnids (Ciliophora) and Other Net Microzooplankton (> 30 µm) in Southwestern Atlantic Shelf Break Waters     

Gustavo A. Thompson  Viviana A. Alder    & Demetrio Boltovskoy   《Marine Ecology》2001,22(4):343-355

Abstract. Proportions of foraminifers, tintinnids, polycystine radiolarians, pteropods and crustacean larval stages were estimated in a collection of 76 vertically stratified (0 – 100 m) 30 µm net microplankton samples from 16 stations along the Argentine shelf-slope (around 200 m isobath – between 40 and 56° S), covered on 13 – 18 November 1996. Tintinnids were identified to species. Relative abundances of the microzooplankton assessed and chlorophyll a values allow to define two contrasting groups of stations: 'deep' and 'shallow'. The former, located in pelagic, purely subantarctic Malvinas Current waters, hosted higher proportions of foraminifers and lower proportions of tintinnids, as well as less chlorophyll a (all differences were significant at the 0.1 % level). 'Shallow' stations were located in the area of the thermohaline front where the Patagonian Current comes in contact with the Malvinas Current, and were generally characterized by higher chlorophyll a levels (up to 3.7 µg Chl a  · l^–1). The distribution of tintinnid species, on the other hand, allowed no discrimination between these two areas, although some of the dominant forms showed much higher relative abundances in one of the two groups of stations. Twenty-six tintinnid taxa were recorded, yet only 6 accounted for 95 % of the specimens identified. Tintinnid taxocoenoses were characterized by a few abundant species and many rare ones. Numbers of tintinnid species and specific diversity did not differ noticeably with depth and latitude. Cape Horn Current waters were detected in the area by the presence of expatriated organisms presumably originating at mid-latitudes in the South Pacific Ocean.  相似文献   

Quantifying the impact of no-till on runoff in southern Brazil at hillslope and catchment scales     

Ana L. Londero  Jean P. G. Minella  Fabio J. A. Schneider  Dinis Deuschle  Danrlei Menezes  Olivier Evrard  Madalena Boeni  Gustavo H. Merten 《水文研究》2021,35(3):e14094

No-till (NT) is a conservation system that improves the hydrological regime of agricultural slopes by providing greater surface protection and benefits to the physical and hydrological properties of soils. However, the isolated use of NT is not enough to control runoff and its associated degradation processes. Therefore, this study aimed to evaluate the runoff of agricultural slopes under NT under different runoff control conditions by monitoring 63 rainfall events in two 2.4-ha zero-order catchments and 27 rainfall events in four 0.6-ha macroplots. The catchments are paired and similar in terms of the type of soil and relief, but different regarding the presence of terraces. The macroplots have different soil and crop management systems. By using monitoring techniques, the hyetographs and hydrographs revealed the influence of the different types of management on the catchments and macroplots and allowed rainfall characteristics, runoff volume, runoff coefficients, water infiltration, peak runoff, response times, and curve number to be analysed. The terraces positively affected the NT and controlled runoff and related variables, in addition to infiltration significantly increasing and runoff reducing in the terraced catchment. All the hydrological information assessed pointed to the positive effects provided by the presence of the terraces. The results in the macroplots showed that high amounts of phytomass and/or chiselling do not control runoff and its correlated variables in medium and high magnitude events. The study concludes by underlining the need for additional measures to control runoff (terraces), even in areas under NT and with high phytomass production. Additionally, the study emphasizes the importance of monitoring at the catchment scale to better understand the hydrological behaviour of agricultural areas and provide the necessary parameters to effectively control runoff.  相似文献   

Effect of solar radiation and the subsequent dark periods on two newly isolated and characterized Antarctic marine bacteria     

Edgardo A. Hernández  Gustavo A. Ferreyra  Walter P. Mac Cormack 《Polar research》2004,23(1):67-77

Two strains of psychrotolerant Antarctic marine bacteria were isolated and characterized using biochemical and molecular techniques. Sequencing of 16S rRNA gene showed that UVvi strain belongs to the genus Arthrobacter whereas UVps strain is related to the Flexibacter-Cytophaga-Bacteroides (FCB) group. Response of the strains to solar radiation was studied during the summer of 1999 in Potter Cove, near Jubany station (South Shetland Island, Antarctica). The effect of photosynthetically available radiation (PAR, 400-700 nm), ultraviolet-A (UV-A, 320-400 nm) and ultraviolet-B radiation (UV-B, 280-320 nm) on cell viability was studied using mixed cultures in quartz bottles covered with interferential filters and exposed to solar radiation. In all experiments, four treatments were used: dark (with light screened out), PAR (with UV radiation screened out), PAR+UV-A (UV-B screened out) and PAR+UV-A+UV-B. Under the assayed conditions, PAR+UV-A and PAR+UV-A+UV-B radiation showed similar negative effects on the viability of the studied strains. However, at the end of the exposure time, mortality values in PAR+UV-A+UV-B treatments were higher than those observed under PAR+UV-A treatments. In both PAR+UV-A and PAR+UV-A+UV-B treatments we observed high levels of hydrogen peroxide compared with the dark control. The Arthrobacter UVvi strain showed significant recovery in dark conditions after exposure to the PAR+UV-A but not after the PAR+UV-A+UV-B treatment. This strain proved to be more resistant to UV radiation than the FCB group-related UVps strain. The results showed that UV radiation has a deleterious effect on these Antarctic marine bacteria and also revealed that the analysed components of the Antarctic bacterioplankton may have different responses when they are exposed to the same irradiance conditions.  相似文献   

The usefulness of UV–visible and fluorescence spectroscopies to study the chemical nature of humic substances from soils and composts   总被引：1，自引：1，他引：1  

Marta Fuentes  Gustavo Gonzlez-Gaitano  Jos Ma García-Mina 《Organic Geochemistry》2006,37(12):1949

The aim of this work is to study the suitability of the use of fluorescence and UV–visible spectroscopies to evaluate the humification degree of different organic alkaline extracts obtained from diverse materials (humic substances, composted and non-composted materials). Our results indicate that the complementary utilization of the fluorescence index proposed by Milori et al. [Milori, D., Martin-Neto, L., Bayer, C., Mielniczuk, J., Vagnato, V., 2002. Humification degree of soil humic acids determined by fluorescence spectroscopy. Soil Science, 167, 739–749] (the total area of the emission spectra collected over a range of 460–650 nm using an excitation wavelength of 465 nm), the ratio between the electron-transfer band and benzenoid band of benzene UV light absorption, and the molar absorption coefficients at 600 nm and 280 nm proved capable of discriminating between extracts obtained from non-humified, partially humified and very humified materials.Likewise, our results suggest that humification is related to increments in the aromatic character of the molecules, which may be reflected in the presence of more aromatic rings and/or more condensed polyaromatic structures, and the degree of substitution in aromatic rings with polar functional groups, as well as to the possible increase in the conjugation degree in unsaturated aliphatic chains.  相似文献   

Taxonomy, facies relationships and palaeobiology of bakevelliid bivalves from the Lower Cretaceous of west-central Argentina     

Darío Gustavo Lazo   《Cretaceous Research》2003,24(6):765

Cretaceous bakevelliids in Argentina are restricted to the Lower Cretaceous. They are recorded in shallow marine deposits in two Mesozoic basins located in the Andes foothills in Patagonia. In the Austral Basin (44°–55°S) there is only one genus, Gervillella, represented by a single specimen from the Barremian. In the Neuquén Basin (30°–40°S) two genera, Gervillaria and Gervillella, occur, ranging from the Berriasian to the Lower Barremian. In the Pilmatué Member of the Agrio Formation two species are identified: Gervillaria alatior (Imlay) and Gervillella aviculoides (J. Sowerby). The former is also recorded in Mexico while the latter is more widespread, occurring in Europe, Asia, and Africa. In the Bajada del Agrio section they come from eight tabular shell beds located near and on top of shallowing-upwards cycles. They were abundant only in four of these levels. These shell beds are interpreted as having been deposited in the mid-ramp (middle of cycles), and upper mid-ramp (top of cycles). A functional analysis of shells revealed two life habits: epibyssate and endobyssate.  相似文献   

The anticentre old open cluster NGC 1883: radial velocity and metallicity     

Sandro Villanova  Gustavo Baume  Giovanni Carraro 《Monthly notices of the Royal Astronomical Society》2007,379(3):1089-1096

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Controls on herbaceous litter decomposition in the estuarine ecotones of the Florida Everglades     

Gustavo Rubio  Daniel L. Childers 《Estuaries and Coasts》2006,29(2):257-268

The effects of nutrient availability and litter quality on litter decomposition were measured in two oligotrophic phosphorus (P)-limited Florida Everglades esturies, United States. The two estuaries differ, in that one (Shark River estuary) is directly connected to the Gulf of Mexico and receives marine P, while the other (Taylor Slough estuary) does not receive marine P because Florida Bay separates it from the Gulf of Mexico. Decomposition of three macrophytes.Cladium jamaicense, Eleochaaris spp., andJuncus roemerianus, was studied using a litter bag technique over 18 mo. Litter was exposed to three treatments: soil surface+macroinvertebrates (=macro), soil surface without macroinvertebrates (=wet), and above the soil and water (=aerial). The third treatment replicated the decomposition of standing dead leaves. Decomposition rates showed that litter exposed to the wet and macro treatments decomposed significantly faster than the aerial treatment, where atmospheric deposition was the only source of nutrients. Macroinvertebrates had no influence on litter decompostion rates.C. jamaicense decomposed faster at sites, with higher P, andEleocharis spp. decomposed significantly faster at sites with higher nitrogen (N). Initial tissue C:N and C:P molar ratios revealed that the nutrient quality of litter of bothEleocharis spp. andJ. roemerianus was higher thanC. jamaicense, but onlyEleocharis spp. decomposed faster thanC. jamaicense. C. jamaicense litter tended to immobilize P, whileEleocharis spp. litter showed net remineralization of N and P. A comparison with other estuarine and wetland systems revealed the dependence of litter decomposition on nutrient availability and litter quality. The results from this experiment suggest that Everglades restoration may have an important effect on key ecosystem processes in the estuarine ecotone of this landscape.  相似文献   

Interferometric study of NGC 1313     

Gustavo J. Carranza  Estela L. Agüero 《Astrophysics and Space Science》1977,46(1):23-31

The kinematics and structure of NGC 1313 are discussed on the basis of interferometric observations. Several uniformly rotating components, a total mass of 2×10¹⁰ solar masses, and deviations from pure circular movement of an amplitude of almost 20 km s^–1 are found.  相似文献