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En relación con el artículo "El rol del ecólogo ante la actual crisis ambiental", de Gurvich et al., en este número
Paruelo,José;
Ecolog?-a austral , 2009,
Abstract: those of us who work in science have often to face the frustration that the knowledge produced in our labs is not taken into consideration by those who manage natural resources. this is a common feature of all disciplines that do not generate knowledge that gives rise to "appropriable" technological developments. among the factors that contribute to a poor transfer of knowledge, in this article i highlight three of them. first, the lack of a professional profile in the disciplinary formation. second, the "scientific illiteracy" of the society that does not perceive science as a process aimed at understanding the real world and operate on it. lastly, the presence of diverse values and interests within the scientific community makes it very difficult to find unanimous positions.
La caracterización funcional de ecosistemas mediante sensores remotos
J.M. Paruelo
Ecosistemas , 2008,
Abstract: La caracterización funcional de ecosistemas mediante sensores remotos: Los sensores remotos han sido valiosos auxiliares de los ecólogos en las últimas décadas. El uso más frecuente de estas herramientas ha sido la caracterización estructural del paisaje. En general, se ha recurrido a la interpretación visual de imágenes y la clasificación digital. En estos casos, un atributo de la superficie terrestre (por ej. un tipo dado de cobertura) se relaciona con un comportamiento espectral determinado (valores de reflectancia o emisión de la superficie terrestre en distintas longitudes de onda) sin conocer los mecanismos del vínculo. Si bien este uso de la teledetección ha permitido avances importantes en Ecología, parece estar por debajo de su potencial. Entre las diferentes alternativas que permitirían hacer un uso más eficiente de la información generada por sensores a bordo de satélites, en este artículo se pone énfasis en la descripción de procesos biofísicos a nivel de ecosistema a partir de la información registrada por los sensores. Para ello, se discute el vínculo entre los datos registrados por los sensores a bordo de satélites de observación terrestre y dos procesos funcionales del ecosistema: la productividad primaria y la evapotranspiración.
Causar o dejar que ocurra
Hernán, Miguel;Paruelo, Jorge;
Andamios , 2007,
Abstract: among the topics covered by discussion on causation between events is causation that involves omissions. if, by having taken precautions, the robbery would not have occurred, then the omission of not having taken precautions is the cause for the robbery. on the other hand, if the robbery did not take place because of the precautions taken, we say that those precautions are a preventor of the robbery. some kind of mirror relationship has been suggested from which derives that not taking precautions and removing them is equivalent. in this paper, such an equivalence is analyzed and it is shown that it has no support for the cases which involve states of affairs. analyzing causation involves dealing with causation by omission and causation of omission. in the first case, omission to take precautions is the cause of a certain disaster. in the second, having taken such precautions is the cause for not obtaining the mentioned disaster: to take precautions is a preventor of the disaster. it has been pointed out that there exists a mirror relationship between omissions and preventors, giving as a consequence that omitting to establish preventors should be equivalent to removing preventors previously provided. in this paper we analyze this equivalence, and conclude that it cannot be supported when states of affairs take place in the role of causes or of effects.
Causar o dejar que ocurra
Hernán Miguel,Jorge Paruelo
Andamios , 2007,
Abstract: Entre los temas que abarca la discusión sobre la causación entre eventos, se encuentra la causación que involucra omisiones. Si de haber tomado precauciones no habría ocurrido el robo, entonces la omisión en tomar precauciones es causa del robo. En cambio, si el robo no se produjo debido a las precauciones tomadas, decimos que tales precauciones son un preventor del robo. Se ha sugerido cierta relación en espejo de la que se deriva que es equivalente no tomar precauciones a removerlas. En este trabajo se analiza dicha equivalencia y se muestra que no se sostiene para los casos que involucran estados de cosas.
Caracterización funcional de la vegetación del Uruguay mediante el uso de sensores remotos
Baeza,Santiago; Paruelo,José M; Altesor,Alice;
Interciencia , 2006,
Abstract: the normalized difference vegetation index (ndvi) is a spectral index derived from sensors on board of satellites that shows a positive and lineal relationship with the proportion of photosynthetic active radiation absorbed by the canopy. the ndvi is a good estimator of primary productivity, an important ecosystem attribute. in this article the ecosystems of uruguay were characterized on the basis of three attributes derived of the seasonal curve of the ndvi using 20 years of images of the satellites noaa/avhrr (1981-2000). the annual integral of the ndvi (ivn-i), an estimate of the aboveground net primary production; the month of maximal ndvi (ivn-mdm); and the relative range of ndvi (ivn-rrel), attributes that account for the seasonal character of the primary production and reflect critical aspects of the ecosystem functioning, were the calculated attributes. based on their behavior, each portion of the uruguayan territory was classified as an ecosystem functional type (tfe), combining supervised and unsupervised classification methods, together with hierarchical analysis. six tfe that differed significantly among them were identified. the spatial variation of the three attributes was associated mainly to the geomorphologic structure and land use patterns, and not to climatic variables.
La teledetección en estudios ecológicos
J. Cabello,J.M. Paruelo
Ecosistemas , 2008,
Abstract:
Land-Use and Land Cover Dynamics in South American Temperate Grasslands
Germán Baldi,José M. Paruelo
Ecology and Society , 2008,
Abstract: In the Río de la Plata grasslands (RPG) biogeographical region of South America, agricultural activities have undergone important changes during the last 15–18 years because of technological improvements and new national and international market conditions. We characterized changes in the landscape structure between 1985–1989 and 2002–2004 for eight pilot areas distributed across the main regional environmental gradients. These areas incorporated approximately 35% of the 7.5 × 105 km2 of the system. Our approach involved the generation of land-use and land cover maps, the analysis of landscape metrics, and the computation of annual transition probabilities between land cover types. All of the information was summarized in 3383 cells of 8 × 8 km. The area covered by grassland decreased from 67.4 to 61.4% between the study periods. This decrease was associated with an increase in the area of annual crops, mainly soybean, sunflower, wheat, and maize. In some subunits of the RPG, i.e., Flat Inland Pampa, the grassland-to-cropland transition probability was high (pG→C = 3.7 × 10 2), whereas in others, i.e., Flooding Pampa, this transition probability was low (pG→C = 6.7 × 10 3). Our description of the magnitude, direction, and spatial distribution of land-use and land cover changes provides a basis from which to develop spatially explicit scenarios of land cover change.
Las reservas privadas ?son efectivas para conservar las propiedades de los ecosistemas?
Roldán,Mateo; Carminati,Alejandra; Biganzoli,Fernando; Paruelo,José M;
Ecolog?-a austral , 2010,
Abstract: to evaluate the contribution to conservation of private refuges, we compared the ecosystem functioning of this type of conservation (refuge) with contiguous national parks (park) and rural ranches and farms under traditional management (traditional). we assume the park as the reference situation, in as much they constitute the areas with the lowest human intervention. the analysis was based on three descriptors of the seasonal dynamics of the carbon gains, derived from spectral data provided by the modis sensor: the normalized difference vegetation index integral (ndvi-i), a spectral index related to the total carbon gains of the ecosystem; the relative range [rrel: (maximum ndvi-minimum ndvi)/(ndvi-i)], and the month of occurrence of the maximum value of ndvi (mmax). these last two attributes characterize the seasonality and phenology of vegetation. we worked on three contrasting biogeographic regions of argentina [paranaense forest (misiones province), mesopotamic pampa (entre ríos province), interior pampa (córdoba province)]. in the paranaense forest, the refuge presented a lower ndvi-i value than the park, but higher than the traditional (p<0.05). the seasonality of the vegetation carbon gains (rrel) was lower on the park than for the other two managements. in the mesopotamic pampa, the gallery forests were the most productive unit (higher ndvi-i). the refuge presented an intermediate behavior. grasslands presented the highest ndvi-i on the refuge (p<0.05). the emblematic vegetation of this region (the palm savannas), did not differ among managements. the seasonality was lower in the gallery forests of the park. in the interior pampa, the differences between refuge and traditional, both in ndvi-i and rrel, were not significantly different among vegetation types or managements. the mmax did not differ between managements for any of the regions studied. our results showed that for most of the ecosystem attributes considered, the refuge presented values more simil
Evaluating the Consistency of the 1982–1999 NDVI Trends in the Iberian Peninsula across Four Time-series Derived from the AVHRR Sensor: LTDR, GIMMS, FASIR, and PAL-II
Domingo Alcaraz-Segura,Elisa Liras,Siham Tabik,José Paruelo,Javier Cabello
Sensors , 2010, DOI: 10.3390/s100201291
Abstract: Successive efforts have processed the Advanced Very High Resolution Radiometer (AVHRR) sensor archive to produce Normalized Difference Vegetation Index (NDVI) datasets (i.e., PAL, FASIR, GIMMS, and LTDR) under different corrections and processing schemes. Since NDVI datasets are used to evaluate carbon gains, differences among them may affect nations’ carbon budgets in meeting international targets (such as the Kyoto Protocol). This study addresses the consistency across AVHRR NDVI datasets in the Iberian Peninsula (Spain and Portugal) by evaluating whether their 1982–1999 NDVI trends show similar spatial patterns. Significant trends were calculated with the seasonal Mann-Kendall trend test and their spatial consistency with partial Mantel tests. Over 23% of the Peninsula (N, E, and central mountain ranges) showed positive and significant NDVI trends across the four datasets and an additional 18% across three datasets. In 20% of Iberia (SW quadrant), the four datasets exhibited an absence of significant trends and an additional 22% across three datasets. Significant NDVI decreases were scarce (croplands in the Guadalquivir and Segura basins, La Mancha plains, and Valencia). Spatial consistency of significant trends across at least three datasets was observed in 83% of the Peninsula, but it decreased to 47% when comparing across the four datasets. FASIR, PAL, and LTDR were the most spatially similar datasets, while GIMMS was the most different. The different performance of each AVHRR dataset to detect significant NDVI trends (e.g., LTDR detected greater significant trends (both positive and negative) and in 32% more pixels than GIMMS) has great implications to evaluate carbon budgets. The lack of spatial consistency across NDVI datasets derived from the same AVHRR sensor archive, makes it advisable to evaluate carbon gains trends using several satellite datasets and, whether possible, independent/additional data sources to contrast.
La estimación de la superficie agrícola: Antecedentes y una propuesta metodológica
Paruelo,José M; Guerschman,Juan P; Baldi,Germán; Di Bella,Carlos M;
Interciencia , 2004,
Abstract: many socioeconomic and political actors use the estimates of cropped areas to plan, reduce the uncertainty or improve resource allocation. to be trustworthy and useful the estimates should be based on a properly documented method, reproducible in space and in time, independent of the operator and validated. to what extent are the above criteria met in argentina? aside from its usefulness, the available information presents many sources of uncertainty that seriously hamper the estimates. they include problems to assign estimates to defined areas, the possibilities of local reporters to integrate the data over space and time, and the different background, motivation and commitment of the reporters. the comparison of the estimates derived from two independent federal agencies for a particular year showed, for the same area, differences of up to 24% in the wheat cropped area. such a difference is higher than the interannual variations that the estimates are trying to describe. multispectral and multitemporal analysis of satellite images allow to discriminate among different land cover types based on their phenology. the combination of remotely sensed data from sensors with different spatial resolution offers enormous possibilities to describe and quantify land cover types and cropping areas. in this article we present an operative protocol, based on the use of landsat tm, sac-c and avhrr/noaa imagery, to evaluate the cropped area of mercosur at the regional scale.
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