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471.
472.
The study area is located in the Pampean region of Argentina, in the northwest of Buenos Aires Province, covering about 50,000 km2, within an area of great plain with particular hydrologic characteristics, where vertical water movements predominate over
horizontal. The objective of this work is the analysis of the relations between different hydrologic scenarios (characterized
by the soil water balance and the water table levels) and the yields of soybeans that have been increasing in recent years.
It is concluded that water table fluctuations are strongly related to the elements of the local hydrologic balance. On the
other hand, the geographic distribution of soybean yields corresponds directly with the values of the soil water reserve during
the critical stages of the growth. After dry periods, the lowering of the water table makes access to water from the root
zone difficult, and the crop is susceptible to the effects of drought. However, after wetter periods the extra contribution
from the water table situated near the surface is favorable for growth, often preventing its deterioration in conditions of
drought. Nevertheless, an excessive rise of the water table can produce disadvantages at seedtime and during harvest. The
importance of an evaluation of the different scenarios that may have significant implications for agricultural activity is
discussed. 相似文献
473.
474.
475.
Eduardo de Mulder Edward Derbyshie Ted Nield 《《幕》》2008,31(2):268-269
The Global Launch Event of the International Year of Planet Earth (IYPE), proclaimed by the United Nations' General Assembly for 2008, took place on 12 and 13 February 2008 at the Paris headquarters of UNESCO. 相似文献
476.
477.
Eduardo García-Portugués Ana M. G. Barros Rosa M. Crujeiras Wenceslao González-Manteiga José Pereira 《Stochastic Environmental Research and Risk Assessment (SERRA)》2014,28(5):1261-1275
A nonparametric test for assessing the independence between a directional random variable (circular or spherical, as particular cases) and a linear one is proposed in this paper. The statistic is based on the squared distance between nonparametric kernel density estimates and its calibration is done by a permutation approach. The size and power characteristics of various variants of the test are investigated and compared with those for classical correlation-based tests of independence in an extensive simulation study. Finally, the best-performing variant of the new test is applied in the analysis of the relation between the orientation and size of Portuguese wildfires. 相似文献
478.
The possibility of using global mean near-surface temperature, its rate of change or the global mean ocean heat-flux as predictors to statistically estimate the change of global mean sea-level is explored in the context of a long climate simulation of the past millennium with the climate model ECHO-G. Such relationships have recently been proposed to by-pass the difficulty of estimating future sea-level changes based on simulations with coarse-resolution climate models. It is found that, in this simulation, a simple linear relationship between mean temperature and the rate of change of sea level does not exist. A regression parameter linking both variables, and estimated in sliding 120-year windows, varies widely along the simulation and, in some periods, even attains negative values. The ocean heat-flux and the rate-of-change of mean temperature seem to better capture the rate-of-change of sea level due to thermal expansion. 相似文献
479.
480.
Large geographic and temporal extensions of the Río de la Plata Craton,South America,and its metacratonic eastern margin 总被引:1,自引:0,他引:1
João O.S. Santos Carlos J. Chernicoff Eduardo O. Zappettini Neal J. McNaughton Léo A. Hartmann 《International Geology Review》2019,61(1):56-85
Integration of existing isotopic and geological data allows a reconsideration of the distribution and age of the Río de la Plata Craton within South America. The reinterpretation increases the area of the craton to about 2,400,000 km2 with implications for the tectonic map of South America and for global reconstruction of palaeocontinents. Four areas previously considered as separate cratons (Luís Alves, Curitiba, Tebicuary, and Paranapanema) are interpreted as part of the same Río de la Plata Craton. The craton is organized into six provinces and domains: Buenos Aires–Piedra Alta, Taquarembó, Tebicuary, Luís Alves, Encantadas, and Nico Pérez. The term ‘Transplatense’ is proposed to replace ‘Trans-Amazonian’ for Rhyacian events that occurred within the Río de la Plata Craton. The craton is formed not only by dominant Rhyacian rocks and local Archaean rocks, but also by Statherian and Mesoproterozoic rocks. The domains are all partially to totally covered by Phanerozoic basins (Paraná, Chacoparanense, Claromecó, Salado, Balcarce, and Colorado) which makes their investigation difficult. The Ediacaran–Cambrian collisions of the Brasilian orogen generated tectonic mixtures of orogenic and cratonic zones. This is more evident in the eastern margin of the craton, which behaved as a metacraton. 相似文献