A 400-year tree-ring record of the Puelo River summer–fall streamflow in the Valdivian Rainforest eco-region, Chile     

Antonio Lara  Ricardo Villalba  Rocío Urrutia 《Climatic change》2008,86(3-4):331-356

The Puelo River is a watershed shared between Chile and Argentina with a mean annual streamflow of 644 m³ s^?1. It has a high ecologic and economic importance, including introduced farmed salmon, tourism, sports fishing and projected hydroelectricity. Using Austrocedrus chilensis and Pilgerodendron uviferum tree-ring records we reconstructed summer–fall (December–May) Puelo River streamflow, which is the first of such reconstructions developed in the Pacific domain of South America. The reconstruction goes back to 1599 and has an adjusted r ² of 0.42. Spectral analysis of the reconstructed streamflow shows a dominant 84-year cycle which explains 25.1% of the total temporal variability. The Puelo River summer–fall streamflow shows a significant correlation (P?>?0.95, 1943–2002) with hydrological records throughout a vast geographic range within the Valdivian eco-region (35 to 46°S). Seasonal Puelo River interannual streamflow variability is related to large-scale oceanic and atmospheric circulation features. Summer–fall streamflows showed a significant negative correlation with the Antarctic Oscillation (AAO), whereas winter–spring anomalies appear to be positively connected with sea surface temperature variations in the tropical Pacific. In general, above- and below-average discharges in winter–spring are related to El Niño and La Niña events, respectively. The temporal patterns of the observed and reconstructed records of the Puelo River streamflow show a general decreasing trend in the 1943–1999 period. Projected circulation changes for the next decades in the Southern Hemisphere would decrease summer–fall Puelo River streamflows with significant impacts on salmon production, tourism and hydropower generation.  相似文献   

Shallow frontal deformation related to active continental subduction: structure and recent stresses in the westernmost Betic Cordillera          下载免费PDF全文

Lourdes González‐Castillo  Jesús Galindo‐Zaldívar  Antonio Pedrera  Francisco José Martínez‐Moreno  Patricia Ruano 《地学学报》2015,27(2):114-121

The westernmost Betic Cordillera front is located along the arcuate alpine belt formed by the interaction of the Eurasian‐African plate boundary and the Alboran continental domain in between. Although classical geological data suggest that the western Cordillera front is inactive, recent GPS data show a westward–north‐westward motion of up to 3.4 mm a^?1 with respect to the foreland. In addition, the increasing thickness of Guadalquivir sedimentary infill towards the Cordillera, and the rectilinear character of the front formed by soft sediments, suggest that the Cordillera is still active. Large ENE–WSW‐oriented open folds detected in the field, seismic reflection profiles and new audiomagnetotellurics data are consistent with active deformation. Fracture analysis in Quaternary deposits evidences recent NW–SE horizontal compression. The GPS motion and maximum stress orientation may be due to north‐westward tectonic collision of the westernmost Betic Cordillera, accommodated at depth by active continental subduction of the Iberian lithosphere.  相似文献   

Wood productivity of Prosopis flexuosa D.C. woodlands in the central Monte: Influence of population structure and tree-growth habit     

J.A. Alvarez  P.E. Villagra  R. Villalba  M.A. ConyM. Alberto 《Journal of Arid Environments》2011,75(1):7-13

A balance between forest production and protection is hard to achieve in arid zones due to their low potential for wood production. Prosopis flexuosa woodlands are the major woody formations in the Monte desert and are currently in a degraded state due to intense use. The main degradation factors in the study area are overgrazing and firewood extraction. We developed allometric models to estimate the aerial biomass of P. flexuosa, compared annual growth rates of one- and multi-stemmed individuals through dendrochronological methods, and estimated the productivity of four structurally different woodlands in the central Monte. Total dry weight was best estimated by power equations. Annual increments in basal area and dry weight were initially larger for multi- than one-stemmed individuals. However, whereas multi-stemmed individuals rapidly decreased their growth rates after 60 years of age, one-stemmed trees maintained steady growth rates during the first 100 years. Depending on woodland density and tree size, total woodland biomass varied between 4000 and 15 000 kg ha⁻¹. Wood productivity was similar in all four woodlands studied (121.6-173.7 kg ha⁻¹ year⁻¹). Our results reveal the importance of tree growth habit to productivity, and suggest that regulated extraction of firewood and poles from old multi-stemmed individuals could optimize wood productivity and contribute to the sustainable use and conservation of these woodlands.  相似文献   

Tree-ring estimates of Pacific decadal climate variability   总被引：10，自引：0，他引：10  

R. D'Arrigo  R. Villalba  G. Wiles 《Climate Dynamics》2001,18(3-4):219-224

 Decadal-scale oscillatory modes of atmosphere-ocean variability have recently been identified in instrumental studies of the Pacific sector. The regime shift around 1976 is one example of such a fluctuation, which has been shown to have significantly impacted climate and the environment along the coastline of the western N and S Americas. The length of meteorological data for the Pacific and western Americas critically limits analyses of such decadal-scale climate variability. Here we present reconstructions of the annual Pacific Decadal Oscillation (PDO) index based on western North American tree-ring records which account for up to 53% of the instrumental variance and extend as far back as AD 1700. The PDO reconstructions indicate that decadal-scale climatic shifts have occurred prior to the period of instrumental record. Evaluation of temperature and precipitation-sensitive tree-ring series from the northeast Pacific as well as these reconstructions reveals evidence for a shift towards less pronounced interdecadal variability after about the middle 1800s. Our analyses also suggest that sites from both the northeast Pacific coast as well as the subtropical Americas need to be included in proxy data sets used to reconstruct the PDO. Received: 15 September 2000 / Accepted: 30 March 2001  相似文献   

Tree-ring and glacial evidence for the medieval warm epoch and the little ice age in southern South America   总被引：3，自引：0，他引：3  

Ricardo Villalba 《Climatic change》1994,26(2-3):183-197

A tree-ring reconstruction of summer temperatures from northern Patagonia shows distinct episodes of higher and lower temperature during the last 1000 yr. The first cold interval was from A.D. 900 to 1070, which was followed by a warm period A.D. 1080 to 1250 (approximately coincident with theMedieval Warm Epoch). Afterwards a long, cold-moist interval followed from A.D. 1270 to 1660, peaking around 1340 and 1640 (contemporaneously with earlyLittle Ice Age events in the Northern Hemisphere). In central Chile, winter rainfall variations were reconstructed using tree rings back to the year A.D. 1220. From A.D. 1220 to 1280, and from A.D. 1450 to 1550, rainfall was above the long-term mean. Droughts apparently occurred between A.D. 1280 and 1450, from 1570 to 1650, and from 1770 to 1820. In northern Patagonia, radiocarbon dates and tree-ring dates record two major glacial advances in the A.D. 1270–1380 and 1520–1670 intervals. In southern Patagonia, the initiation of theLittle Ice Age appears to have been around A.D. 1300, and the culmination of glacial advances between the late 17th to the early 19th centuries.Most of the reconstructed winter-dry periods in central Chile are synchronous with cold summers in northern Patagonia, resembling the present regional patterns associated with the El Niño-Southern Oscillation (ENSO). The years A.D. 1468–69 represent, in both temperature and precipitation reconstructions from treerings, the largest departures during the last 1000 yr. A very strong ENSO event was probably responsible for these extreme deviations. Tree-ring analysis also indicates that the association between a weaker southeastern Pacific subtropical anticyclone and the occurence of El Niño events has been stable over the last four centuries, although some anomalous cases are recognized.  相似文献   

Structure of interacting elliptical radio galaxies     

Lourdes De Juan  Luis Colina  Ismael Pérez-Fournon 《Astrophysics and Space Science》1993,205(1):209-216

We have used a numerical method based on elliptical fitting of isophotes to analyse the structural parameters of three pairs of elliptical galaxies containing radio jets. The relationship between tidal interactions and radio activity is also investigated.  相似文献   

K. Heather Kennedy: Introduction to 3D Data: Modeling with ArcGIS 3D Analyst and Google Earth     

Lourdes V. Abellera 《Mathematical Geosciences》2012,44(3):375-377

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Organic composition of atmospheric urban aerosol: Variations and sources of aliphatic and polycyclic aromatic hydrocarbons   总被引：1，自引：0，他引：1  

Miguel A. Barrero Mazquiarn  Lourdes Cantn Ortiz de Pinedo 《Atmospheric Research》2007,85(3-4):288-299

The non-polar organic composition of airborne particulate matter was analysed over a two year period in an urban area under oceanic climate conditions (Errenteria, Basque Country, Spain). In addition, the distribution of polycyclic aromatic hydrocarbons (PAH) among different aerosol particle sizes was determined. Clues as to the origin of various particle types were gained by using scanning electron microscopy to view the morphology of the particulates in each size fraction. Samples were collected on glass fibre filters and analysed by means of soxhlet extraction and gas chromatography (either with a flame ionization detector or coupled to a mass spectrometry). In general, total PAH levels were moderate (0.96–50 ng m^− 3) as compared to other studies conducted in Europe, and showed clear seasonal variation with maxima in winter and minima in summer. Vehicular traffic was identified as a major source of PAHs in the study area. Regarding particle size, a bimodal distribution was observed. The large sized particles exhibited an apparent seasonal variation with higher concentrations in winter than in summer. The dependences between particle size, PAH distribution and meteorological variables were studied with multivariate statistics. Three main sources of organic compounds were identified: combustion, vegetation, and atmospheric oxidation.  相似文献   

Models of Ground Deformation and Eruption Magnitude from a Deep Source at Popocatepetl Volcano,Central Mexico     

Espíndola  Juan Manuel  De Lourdes Godinez  Maria  Espindola  Victor Hugo 《Natural Hazards》2004,31(1):191-207

Popocatepetl volcano in Central Mexico entered its latest stage of activity in late 1994. Due to the nature of its eruptive history and its location in a heavily populated area, it constitutes the highest risk in the cuntry. For this reason the volcano is currently under continuous surveillance; yet the interpretation of the information is carried out mostly on empirical basis and an integrating working model is lacking, at the present. In this paper, models of elastic deformation and mass erupted are developed to estimate the mass erupted according to the observed deformation patterns. We present results obtained from input based upon a gravimetric model of the volcano's internal structure and reasonable physical parameters of the volcanic system. These results are helpful in the planning of deformation and gravimetric observations aimed to forecast a major eruption.  相似文献   

Political coordination costs in the Spanish port devolution process: A note     

Jose I. Castillo-Manzano  Lourdes López-Valpuesta  Fernando Gonzalez Laxe 《Ocean & Coastal Management》2010,53(9):577-580

Spain’s port system was subjected to significant legislative reforms during the 1990s. Spanish Law 62/97 allowed regional governments to manage commercial ports, whereas the central government continued to control the main organisation in charge of the Spanish port system – the Spanish National Ports and Harbours Authority (SNPHA). This paper analyses the evolution of maritime traffic to measure the possible costs of political coordination between the SNPHA and the port authorities controlled by various political parties that rule regional governments. The findings point to coordination costs having a limited effect on the evolution of maritime traffic.  相似文献