Changes in Climate and Crop Production During the 20th Century in Argentina     

Graciela O. Magrin  María I. Travasso  Gabriel R. Rodríguez 《Climatic change》2005,72(1-2):229-249

This work was focused on the assessment of changes occurring in crop production and climate during the 20th century in Argentina. The study was carried out for nine sites located in the Pampas region that are representative of contrasting environments. We have considered the four main crops cultivated in this area (wheat, maize, sunflower and soybean). Historical climatic data and crop production related variables (yield, planted area, harvested area) were analyzed and, by means of crop simulation models, we quantified the impact of climate on crop yields. Changes occurring in climate during the three last decades of the 20th century were characterized by important increases in precipitation especially between October and March, decreases in maximum temperature and solar radiation in particular during spring and summer and increases in minimum temperature during almost all of the year. These changes contributed to increases in yields, especially in summer crops and in the semiarid zone, mostly due to increases in precipitation, although changes in temperature and radiation also affected crop yields but to a lesser extent. Comparing the period 1950–1970 with 1971–1999, yields increases attributable to changes in climate were 38% in soybean, 18% in maize, 13% in wheat, and 12% in sunflower while mean observed yield increases were 110% for maize, 56% for wheat and 102% for sunflower.  相似文献   

Tephrochronology of recent events in the Andean Range (northern Patagonia): spatial distribution and provenance of lacustrine ash layers in the Nahuel Huapi National Park     

Romina Daga  Sergio Ribeiro Guevara  M. Lidia Sánchez  María Arribére 《第四纪科学杂志》2010,25(7):1113-1123

Tephrochronology is a powerful tool for dating sedimentary sequences, especially in Patagonia, where a large number of active volcanoes have produced frequent historical eruptions. Short lacustrine sedimentary sequences were extracted from the lakes Moreno Oeste and Ton?ek (Nahuel Huapi National Park). Seventeen volcanic ash layers were identified in both cores, ²¹⁰Pb and ¹³⁷Cs were used for dating techniques, and historical volcanic records were employed for correlation. White pumice and glass shards from the tephras were characterised by measuring major and trace element contents by instrumental neutron activation analysis. Two volcanic sources – the Cordón Caulle and the Calbuco volcanoes – were recognised as the prevailing systems that impacted the area in the past 800–1000 a. The Calbuco volcano was mainly responsible for the nine tephras identified in the Lake Ton?ek sequence. Four of these nine tephras also contained material from the Cordón Caulle complex, and could be interpreted as composite tephras or possible reworked ones. The Calbuco volcano showed predominant influences in the Lake Moreno Oeste sequence. Six of the eight tephras identified in such a sequence were from the Calbuco volcano, and three of these six contained material from the Cordón Caulle complex. The other two were from the Cordón Caulle complex, with contributions from the Calbuco volcano in one of them. These findings show that the high frequency of volcanic events in the study region demands an accurate characterisation of the products generated by each source, as well as an evaluation of their spatial distribution, to obtain a consistent framework for dating recent environmental changes. Copyright © 2010 John Wiley & Sons, Ltd.  相似文献   

Sedimentary response of lake El Tobar,Spain, to climate: lake level changes after the Maunder Minimum          下载免费PDF全文

Charo López‐Blanco  Julian Andrews  Paul Dennis  María Rosa Miracle  Eduardo Vicente 《第四纪科学杂志》2016,31(8):905-918

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Modelling evaporation processes in soils from the Huasco salt flat basin,Chile          下载免费PDF全文

María Fernanda Hernández‐López  Isabelle Braud  Jorge Gironás  Francisco Suárez  José Francisco Muñoz 《水文研究》2016,30(25):4704-4719

The need to understand and simulate hydrological phenomena and their interactions, and the impact of anthropogenic and climate changes on natural environments have promoted the study of evaporation from bare soils in arid climates. In closed Altiplano basins, such as those encountered in arid and hyper arid basins in northern Chile, evaporation from shallow groundwater is the main source of aquifer depletion, and thus, its study is crucial for water resources management. The objective of this work is to understand the mechanisms of evaporation in saline soils with shallow water tables, in order to better quantify evaporation fluxes and improve our understanding of the water balance in these regions. To achieve this objective, a model that couples fluid flow with heat transfer was developed and calibrated using column experiments with saline soils from the Huasco salt flat basin, Chile. The model enables determination of both liquid and water vapour fluxes, as well as the location of the evaporation front. Experimental results showed that salt transport inside the soil profile modified the water retention curve, highlighting the importance of including salt transport when modelling the evaporation processes in these soils. Indeed, model simulations only agreed with the experimental data when the effect of salt transport on water retention curves was taken into account. Model results also showed that the evaporation front is closer to the soil surface as the water table depth reduces. Therefore, the model allows determining the groundwater level depth that results in disconnection of liquid fluxes in the vadose zone. A sensitivity analysis allowed understanding the effect of water‐flux enhancements mechanisms on soil evaporation. The results presented in this study are important as they allow quantifying the evaporation that occurs in bare soils from Altiplano basins, which is typically the main water discharge in these closed basins. Copyright © 2016 John Wiley & Sons, Ltd.  相似文献   

The identification of an appropriate Minimum Inter‐event Time (MIT) based on multifractal characterization of rainfall data series          下载免费PDF全文

M. T. Medina‐Cobo  A.P. García‐Marín  J. Estévez  J.L. Ayuso‐Muñoz 《水文研究》2016,30(19):3507-3517

Different hydrological models of sediment entrainment, infiltration, overland flow production, soil loss, landslide occurrence, among others, need rainfall events data. The Minimum Inter‐event Time (MIT) used to separate rainfall events affects their properties. Therefore, it is highly important their correct definition. Various event definitions are commonly used in hydrology, and a high variety of MIT is applied. In this work, an easy method is proposed for deciding the proper MIT in a certain place when dealing with hourly rainfall data series. This new methodology is based on the scale invariance properties of rainfall, analysed with both multifractal and Self‐Organized Criticality theories. The similarity between some parameters from both analyses allows picking out the more appropriate MIT for the hourly rainfall data sets analysed, in Malaga (Southern Spain) and Bullileo (Central Chile). The method can be applied for different rainfall time resolutions according to the purpose of the model that needs the rain event information. Copyright © 2016 John Wiley & Sons, Ltd.  相似文献   

Determining the vertical evolution of hydrodynamic parameters in weathered and fractured south Indian crystalline-rock aquifers: insights from a study on an instrumented site     

A. Boisson  N. Guihéneuf  J. Perrin  O. Bour  B. Dewandel  A. Dausse  M. Viossanges  S. Ahmed  J. C. Maréchal 《Hydrogeology Journal》2015,23(4):757-773

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Determination of the Concentration of Carbonic Species in Natural Waters: Results from a World‐Wide Proficiency Test          下载免费PDF全文

Mahendra P. Verma  Enrique Portugal  Sophie Gangloff  María Aurora Armienta  Dornadula Chandrasekharam  Mayela Sanchez  Roberto E. Renderos  Miguel Juanco  Robert van Geldern 《Geostandards and Geoanalytical Research》2015,39(2):233-255

The results of an international interlaboratory proficiency test for the determination of carbonic species are presented. Eight laboratories analysed twelve water samples (four synthetic waters, one lake water, four geothermal waters, one seawater and two petroleum waters) by two methods: (a) individual laboratory analytical procedure and (b) acid–base titration curves in tabular form following a standardised protocol. In case (b), the concentrations of carbonic species were calculated by the organiser using the (1) Hydrologists' method, (2) Geochemists' method and/or (3) initial pH and total alkalinity method. For synthetic waters, the averaged % trueness and precision of measurement of the two methods were (trueness = 7.6, precision = 9.4) and (9.0, 3.4) for total alkalinity, and (6.6, 31.0) and (7.8, 6.1) for carbonic alkalinity, respectively. This indicates that the total alkalinity calculation procedure is in general correct in the individual laboratory method, but the carbonic alkalinity calculation procedure has serious problems. The measurements of total alkalinity for lake and seawaters were in agreement in both the methods; however, the individual laboratory measurement method for geothermal and petroleum waters was conceptually incorrect. Thus, the analytical procedures for the determination of carbonic species were reviewed. To apply the Hydrologists' and/or Geochemists' methods, the location of NaHCO₃EP and H₂CO₃EP is necessary, even for samples with pH lower than that of NaHCO₃EP, and a backward titration curve after complete removal of CO₂ must be performed. The initial pH and total alkalinity method is appropriate where a complete analysis of species that contribute to the alkalinity is known.  相似文献   

Scale dependence in habitat selection: the case of the endangered brown bear (Ursus arctos) in the Cantabrian Range (NW Spain)     

María C. Mateo Sánchez  Samuel A. Cushman  Santiago Saura 《International journal of geographical information science》2014,28(8):1531-1546

Animals select habitat resources at multiple spatial scales. Thus, explicit attention to scale dependency in species–habitat relationships is critical to understand the habitat suitability patterns as perceived by organisms in complex landscapes. Identification of the scales at which particular environmental variables influence habitat selection may be as important as the selection of variables themselves. In this study, we combined bivariate scaling and Maximum entropy (Maxent) modeling to investigate multiscale habitat selection of endangered brown bear (Ursus arctos) populations in northwest Spain. Bivariate scaling showed that the strength of apparent habitat relationships was highly sensitive to the scale at which predictor variables are evaluated. Maxent models on the optimal scale for each variable suggested that landscape composition together with human disturbances was dominant drivers of bear habitat selection, while habitat configuration and edge effects were substantially less influential. We found that explicitly optimizing the scale of habitat suitability models considerably improved single-scale modeling in terms of model performance and spatial prediction. We found that patterns of brown bear habitat suitability represent the cumulative influence of habitat selection across a broad range of scales, from local resources within habitat patches to the landscape composition at broader spatial scales.  相似文献   

Technical Evaluation of Glauconies as Alternative Potassium Fertilizer from the Salamanca Formation,Patagonia, Southwest Argentina     

Corina Franzosi  Liliana N. Castro  Ana María Celeda 《Natural Resources Research》2014,23(3):311-320

The aim of this work was to evaluate the Salamanca Formation greensands as an alternative potassium fertilizer to KCl. Glauconitic pellets from this formation tend to naturally concentrate in 600–250 μm (BS 250) and 250–125 μm (BS 125) fractions. After dry sieving and magnetic separation, these fractions were used for chemical, lixiviation, and specific surface analyses and agronomic evaluations. Two concentrated products were obtained: GL250c (600–250 μm) and GL125c (250–125 μm) representing 40.9 % of total sample. GL250c contains 2.97 % K₂O, and GL125c contains 4.05 % K₂O, representing 27 and 60 % increase in K-content compared to the bulk sample. Grain size of both concentrates decreased significantly through lixiviation tests. Potassium release curves from lixiviation waters show that K-liberation from GL250c was more effective in the first 15 days but decreased after that whereas liberation from GL125c continued to increase after 15 days probably due to higher K-content (36 % higher than GL250c). Specific area could have influenced liberation rates because after leaching it increased 27 % for the finer fraction and by only 16 % for the coarser one. From agronomic assays, measured over 75 days with five harvests, the first four harvests yield best results from KCl probably due to fast K-liberation rates from the salt. However, after overall harvests, fertilization efficiency using either GL250c or GL125c was very similar to and slightly higher than KCl fertilization. As equivalent results were found using either GL250c or GL125c, sieving to obtain these fractions seems not necessary. The results indicate that greensands from the Salamanca Formation are effective slow release alternative K source for fertilizers with low cost of production and treatment compared to operation costs required for mining K soluble salts at depth.  相似文献   

Biodiversity,ecological structure,and change in the sponge community of different geomorphological zones of the barrier fore reef at Carrie Bow Cay,Belize     

Estrella Villamizar  María C. Díaz  Klaus Rützler  Renato De Nóbrega 《Marine Ecology》2014,35(4):425-435

Changes in the relative abundance of benthic groups on the barrier fore reef at Carrie Bow Cay, Belize, point to a significant reduction of corals and an expansion of the sponge community in 1995–2009. Fifty‐one species are now present in the four geomorphological zones of this reef: the low‐relief spur‐and‐groove zone, the inner reef slope, the outer ridge, and the fore‐reef slope (to a depth of 30 m). Five species are new additions to the sponge fauna reported for Belize, and six species account for 42.6% of the total assemblage: Niphates erecta (9.60%), Aiolochroia crassa (8.8%), Niphates digitalis (6.9%), Callyspongia plicifera (6.63%), Aplysina archeri (5.37%) and Xestospongia muta (5.37%). Species richness, average density, diversity and evenness indexes are statistically similar in these four zones but some species appear to be more dominant in certain areas. In the same 30 years, coral cover has decreased by more than 90%, while the octocoral cover has greatly increased (by as much as 10‐fold in the low‐relief spur‐and‐groove zone). Thus the Carrie Bow fore reef appears to be undergoing a transition from coral dominance in the late 1970s to algae dominance today, with other benthic groups such as sponges and octocorals showing signs of gradual recovery.  相似文献