Throughfall patterns in sugarcane and riparian forest: understanding the effect of sugarcane age and land use conversion          下载免费PDF全文

Robson Willians da Costa Silva  Luiz Felippe Salemi  Rafael Pires Fernandes  Tatiana Morgan Berteli de Andrade  Jorge Marcos de Moraes  Plínio Barbosa de Camargo  Luiz Antonio Martinelli 《水文研究》2016,30(15):2579-2589

Sugarcane is an annual crop with a dynamic canopy that changes over time mainly because of genetic adaptation. There is uncertainty about the temporal trends of throughfall (TF) in this important commercial crop. In the present paper, we used troughs to measure TF in a third and fourth ratoon and subsequently in a fourth and fifth ratoon. Additional measurements were carried out in an adjacent riparian forest. There were no significant differences between cycles of sugarcane, growth phases and riparian forest. The TF results for ratoon crop and riparian forest in 2011/2012 were 76% and 79.5% of gross rainfall, respectively, while in 2012/2013, they were 79% and 78%, respectively. However, TF was remarkably lower in the riparian forest relative to ratoon from the second half of the culm formation and elongation phase (280 days after harvest) until harvest. Copyright © 2016 John Wiley & Sons, Ltd.  相似文献   

Dynamics of the January 2013–June 2014 explosive-effusive episode in the eruption of Volcán de Colima,México: insights from seismic and video monitoring     

Vyacheslav M. Zobin  Raúl Arámbula  Mauricio Bretón  Gabriel Reyes  Imelda Plascencia  Carlos Navarro  Armando Téllez  Arnoldo Campos  Miguel González  Zoraida León  Alejandro Martínez  Carlos Ramírez 《Bulletin of Volcanology》2015,77(4):1-13

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Improved algorithms for generalized finite element simulations of three-dimensional hydraulic fracture propagation     

Nathan Shauer  Carlos Armando Duarte 《国际地质力学数值与分析法杂志》2019,43(18):2707-2742

This paper reports improvements to algorithms for the simulation of 3-D hydraulic fracturing with the Generalized Finite Element Method (GFEM). Three optimizations are presented and analyzed. First, an improved initial guess based on solving a 3-D elastic problem with the pressure from the previous step is shown to decrease the number of Newton iterations and increase robustness. Second, an improved methodology to find the time step that leads to fracture propagation is proposed and shown to decrease significantly the number of iterations. Third, reduced computational cost is observed by properly recycling the linear part of the coupled stiffness matrix. Two representative examples are used to analyze these improvements. Additionally, a methodology to include the leak-off term is presented and verified against asymptotic analytical solutions. Conservation of mass is shown to be well satisfied in all examples.  相似文献   

Importance of mixotrophic nanoplankton in Aysén Fjord (Southern Chile) during austral winter     

Till Czypionka  Cristian A. Vargas  Nelson Silva  Giovanni Daneri  Humberto E. González  José Luis Iriarte 《Continental Shelf Research》2011,31(3-4):216-224

Mixotrophy, the combination of autotrophic and heterotrophic nutrition in the same organism, is widespread in planktonic algae. Several reports from temperate and high-latitude fjords in Scandinavia suggest the occurrence of a niche in late summer and autumn during post-bloom conditions in which mixotrophic algae can become important grazers in pelagic ecosystems, accessing the nutrients bound in their prey to overcome nutrient limitation. Here, we experimentally determined the trophic modes and bacterivory rates for the nanoplankton community (2–20 μm) in Aysén Fjord located in the Chilean Northern Patagonia during two contrasting seasons: winter and spring. While mixotrophic nanoplankton was virtually absent from the system in spring, in winter at occasions it even constituted the dominant trophic group of the nanoplankton with abundances of >900 cells mL^?1. This indicates a second niche for mixotrophs in winter, when mixotrophy allows overcoming light limitation.  相似文献   

Lake sedimentary processes and vegetation changes over the last 45k cal a bp in the uplands of south-eastern Amazonia     

José Tasso Felix Guimarães  Prafulla Kumar Sahoo  Mariana Maha Jana Costa De Figueiredo  Karen da Silva Lopes  Markus Gastauer  Silvio Junio Ramos  Cecilio Frois Caldeira  Pedro Walfir M. Souza-Filho  Luiza Santos Reis  Marcio Sousa Da Silva  Paulo Rogenes Pontes  Renato Oliveira Da Silva Junior  Tarcísio Magevski Rodrigues 《第四纪科学杂志》2021,36(2):255-272

This study addresses paleoclimate influences in a southern Amazonia ecotone based on multiproxy records from lakes of the Carajás region during the last 45k cal a bp. Wet and cool environmental conditions marked the initial deposition in shallow depressions with detrital sediments and high weathering rates until 40k cal a bp. Concomitantly, forest and C3 canga plants, along with cool-adapted taxa, developed; however, short drier episodes enabled expansion of C4 plants and diagenetic formation of siderite. A massive event of siderite formation occurred approximately 30k cal a bp under strong drier conditions. Afterwards, wet and cool environmental conditions returned and persisted until the Last Glacial Maximum (LGM). The LGM was marked by lake-level lowstands and subaerial exposure. The transition from the LGM to the Holocene is marked by the onset of oscillations in temperature and humidity, with an expansion of forest and canga plants. Cool taxa were present for the last time in the Carajás region ~ 9.5–9k cal a bp. After 10k cal a bp , shallow lakes became upland swamps due to natural infilling processes, but the current vegetation types and structures of the plateaus were acquired only after 3k cal a bp under wetter climatic conditions.  相似文献   

Coastal Occupations in Tierra del Fuego,Southernmost South America: A Late Holocene Hunter‐Gatherer Context at Marazzi 2     

Ivana L. Ozn  Charles French  Flavia Morello Repetto  Carlos A. Vsquez  Toms Luppo 《Geoarchaeology》2015,30(6):465-482

This paper focuses on the late Holocene occupation of hunter‐gatherers at the Marazzi 2 site located on the northwestern steppe of Tierra del Fuego, Chile. Our aim is to understand stratigraphy, formation processes, and pedogenesis with respect to human occupation over the last 3000 years. Based on archaeological excavations on a fluvial terrace of the Torcido River, we integrate soil micromorphology, mineralogy, geochemistry, magnetic susceptibility, and geomorphology, as well as the micro‐ and macrofrequency distributions of archaeological material. A micro‐taphonomical perspective is also applied to anthropogenic components recorded in sedimentary thin sections. We discuss various events in the interplay between soil development and human occupation through time. Marazzi 2 was witness to aggradation and pedogenesis with an episode of surface stability coincident with a phase of more intense human occupation at about 860 BC. Taphonomic analysis suggests that there are multiple occupation events mixed together, probably by biomechanical processes, resulting in a palimpsest with poor temporal resolution.  相似文献   

Analysis of extreme rainfall in the Ebre Observatory (Spain)     

Núria Pérez-Zanón  M. Carmen Casas-Castillo  Raúl Rodríguez-Solà  Juan Carlos Peña  Anna Rius  J. Germán Solé  Ángel Redaño 《Theoretical and Applied Climatology》2016,124(3-4):935-944

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Using a regional numerical weather prediction model for GNSS positioning over Brazil     

Daniele Barroca Marra Alves  Luiz Fernando Sapucci  Haroldo Antonio Marques  Eniuce Menezes de Souza  Tayná Aparecida Ferreira Gouveia  Jackes Akira Magário 《GPS Solutions》2016,20(4):677-685

The global navigation satellite system (GNSS) can provide centimeter positioning accuracy at low costs. However, in order to obtain the desired high accuracy, it is necessary to use high-quality atmospheric models. We focus on the troposphere, which is an important topic of research in Brazil where the tropospheric characteristics are unique, both spatially and temporally. There are dry regions, which lie mainly in the central part of the country. However, the most interesting area for the investigation of tropospheric models is the wet region which is located in the Amazon forest. This region substantially affects the variability of humidity over other regions of Brazil. It provides a large quantity of water vapor through the humidity convergence zone, especially for the southeast region. The interconnection and large fluxes of water vapor can generate serious deficiencies in tropospheric modeling. The CPTEC/INPE (Center for Weather Forecasting and Climate Studies/Brazilian Institute for Space Research) has been providing since July 2012 a numerical weather prediction (NWP) model for South America, known as Eta. It has yield excellent results in weather prediction but has not been used in GNSS positioning. This NWP model was evaluated in precise point positioning (PPP) and network-based positioning. Concerning PPP, the best positioning results were obtained for the station SAGA, located in Amazon region. Using the NWP model, the 3D RMS are less than 10 cm for all 24 h of data, whereas the values reach approximately 60 cm for the Hopfield model. For network-based positioning, the best results were obtained mainly when the tropospheric characteristics are critical, in which case an improvement of up to 7.2 % was obtained in 3D RMS using NWP models.  相似文献   

A new method for specular and diffuse pseudorange multipath error extraction using wavelet analysis     

Giovanni?Pugliano  Umberto?RobustelliEmail authorView author&#;s OrcID profile  Fabio?Rossi  Raffaele?Santamaria 《GPS Solutions》2016,20(3):499-508

Multipath remains one of the major challenges in Global Navigation Satellite System (GNSS) positioning because it is considered the dominant source of ranging errors, which can be classified into specular and diffuse types. We present a new method using wavelets to extract the pseudorange multipath in the time domain and breaking it down into the two components. The main idea is an analysis-reconstruction approach based on application of both continuous wavelet transform (CWT) and discrete wavelet transform (DWT). The proposed procedure involves the use of L1 code-minus-carrier (CMC) observable where higher-frequency terms are isolated as residuals. CMC residuals are analyzed by applying the CWT, and we propose the scalogram as a technique for discerning time–frequency variations of the multipath signal. Unlike Fourier transform, the potential of the CWT scalogram for examining the non-stationary and multifrequency nature of the multipath is confirmed as it simultaneously allows fine detection and time localization of the most representative frequencies of the signal. This interpretation of the CWT scalogram is relevant when choosing the levels of reconstruction with DWT, allowing accurate time domain extraction of both the specular and diffuse multipath. The performance and robustness of the method and its boundary applicability are assessed. The experiment was carried out using a receiver of Campania GNSS Network. The results are given in which specular multipath error is achieved using DWT level 7 approximation component and diffuse multipath error is achieved using DWT level 6 denoised detail component.  相似文献   

Local indices for the South American monsoon system and its impacts on Southeast Brazilian precipitation patterns     

David Marcolino Nielsen  Marcio Cataldi  André Luiz Belém  Ana Luiza Spadano Albuquerque 《Natural Hazards》2016,81(2):909-938

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