Temperate rainforest response to climate change and disturbance agents in northwestern Patagonia (41°S) over the last 2600 years     

Ignacio A. Jara  Patricio I. Moreno 《Quaternary Research》2012,77(2):235-244

We present detailed pollen and charcoal records from Lago Pichilafquén (~ 41°S) to decipher the effects of climate change and varying disturbance regimes on the composition and structure of the vegetation on the Andean foothills of northwestern Patagonia during the last 2600 yr. Here, temperate rainforests have dominated the landscape since 2600 cal yr BP with variations ranging from cool-temperate and wet north Patagonian rainforests to relatively warm and summer-drought-resistant Valdivian rainforests. We interpret relatively warm/dry conditions between 1900–2600, 690–750 and 320–430 cal yr BP, alternating with cold/wet conditions between 1500–1900, 750–1100 and 430–690 cal yr BP. Rapid deforestation and spread of plants introduced by Europeans occurred at 320 and 140 cal yr BP. The record includes five tephras with ages of 2130, 1460, 1310, 1210, and 340 cal yr BP, all of which precede local fire events and increases in trees favored by disturbance by less than 100 yr. We conclude that centennial-scale changes in the southern westerlies were the primary driver of vegetation shifts in northwestern Patagonia over the last 2600 yr. Within this interval, local disturbance regimes altered the structure, composition, and dynamics of the lowland rainforest vegetation during several discrete, short-lived episodes.  相似文献   

California coastal management with a changing climate   总被引：2，自引：0，他引：2  

Ellen Hanak  Georgina Moreno 《Climatic change》2012,111(1):45-73

With over 2,000 miles (3,218 km) of ocean and estuarine coastline, California faces significant coastal management challenges as a result of climate change-induced sea level rise. Under high emission scenarios, recent models predict 1.4 m or more of sea level rise by 2100, accompanied by increasing storm surges. This article investigates the most important issues facing coastal managers, explores the policy tools available for adapting to the impacts of climate change, assesses institutional constraints to adaptation, and identifies priorities for future research and policy action. We find that adaptation tools exist for dealing with anticipated increases in coastal erosion and flooding, but they involve significant costs and tradeoffs. In particular, coastal armoring, such as seawalls, can protect developed coastal lands, but destroys beaches and habitat. Although California already has policies and institutions that aim to balance the competing objectives for coastal development, management agencies are at the early stages of understanding how to facilitate adaptation. Research priorities to inform coastal adaptation planning include: (i) inventorying coastal resources to provide a firmer basis for balancing decisions on property and habitat protection, (ii) identifying opportunities for coastal habitat migration, (iii) assessing the vulnerabilities of existing and planned coastal infrastructure, and (iv) experimenting with alternatives to armoring as a way of managing the changing coastline.  相似文献   

Lateglacial and Holocene palaeohydrology in the western Mediterranean region: The Lake Estanya record (NE Spain)   总被引：3，自引：0，他引：3  

Mario Morelln  Blas Valero-Garcs  Teresa Vegas-Vilarrúbia  Penlope Gonzlez-Sampriz   scar Romero  Antonio Delgado-Huertas  Pilar Mata  Ana Moreno  Mayte Rico  Juan Pablo Corella 《Quaternary Science Reviews》2009,28(25-26):2582-2599

The multi-proxy analysis of sediment cores recovered in karstic Lake Estanya (42°02′ N, 0°32′ E; 670 m a. s. l., NE Spain), located in the transitional area between the humid Pyrenees and the semi-arid Central Ebro Basin, provides the first high-resolution, continuous sedimentary record in the region, extending back the last 21 000 years. The integration of sedimentary facies, elemental and isotopical geochemistry and biogenic silica, together with a robust age model based on 17 AMS radiocarbon dates, enables precise reconstruction of the main hydrological and environmental changes in the region during the last deglaciation.Arid conditions, represented by shallow lake levels, predominantly saline waters and reduced organic productivity occurred throughout the last glacial maximum (21–18 cal kyrs BP) and the lateglacial, reaching their maximum intensity during the period 18–14.5 cal kyrs BP (including Heinrich event 1) and the Younger Dryas (12.9–11.6 cal kyrs BP). Less saline conditions characterized the 14.5–12.6 cal kyrs BP period, suggesting higher effective moisture during the Bölling/Allerød. The onset of more humid conditions started at 9.4 cal kyrs, indicating a delayed hydrological response to the onset of the Holocene which is also documented in several sites of the Mediterranean Basin. Higher, although fluctuating, Holocene lake levels were punctuated by a mid Holocene arid period between 4.8 and 4.0 cal kyrs BP. A major lake-level rise occurred at 1.2 cal kyrs BP, conducive to the establishment of conditions similar to the present and interrupted by a last major water level drop, occurring around 800 cal yrs BP, which coincides with the Medieval Climate Anomaly.The main hydrological stages in Lake Estanya are in phase with most Western Mediterranean and North Atlantic continental and marine records, but our results also show similarities with other Iberian and northern African reconstructions, emphasizing peculiarities of palaeohydrological evolution of the Iberian Peninsula during the last deglaciation.  相似文献   

The AD 1300–1700 eruptive periods at Tungurahua volcano,Ecuador, revealed by historical narratives,stratigraphy and radiocarbon dating     

J.-L. Le Pennec  D. Jaya  P. Samaniego  P. Ramón  S. Moreno Yánez  J. Egred  J. van der Plicht 《Journal of Volcanology and Geothermal Research》2008

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Abrupt Vegetation and Climate Changes During the Last Glacial Maximumand Last Termination in The Chilean Lake District: A Case Study from Canal De La Puntilla (41°S)     

P.I. Moreno  T.V. Lowell  G.L. Jacobson Jr  & G.H. Denton 《Geografiska Annaler: Series A, Physical Geography》1999,81(2):285-311

ABSTRACT. Multiple overlapping and replicate pollen stratigraphies from Canal de la Puntilla (40°57’09”S, 72°54’18”W, 120 m elevation) reveal that a Nothofagus dombeyi-type parkland occupied the Valle Central of the Chilean Lake District during the portion of the Last Glacial Maximum between 20,200 and about 14,600 ¹⁴C yr BP . Dominating this landscape was Nothofagus dombeyi-type and Gramineae, accompanied by taxa commonly found today in Subantarctic environments and above the Andean tree-line in the Lake District (Perezia-type, Valeriana, and Huperzia selago), along with cushion bog taxa characteristic of Magellanic Moorlands (Donatia fascicularis and Astelia pumila). Within this open landscape Nothofagus dombeyi-type expanded between 20,200 and 15,800 ¹⁴C yr BP , interrupted by a brief reversal between 19,200 and 18,800 ¹⁴ C yr BP and followed by a prominent increase in Gramineae pollen between 15,800 and about 14,600 ¹⁴C yr BP . A major rise of Nothofagus dombeyi-type began at about 14,600 ¹⁴C yr BP , followed by decline in non-arboreal taxa and a remarkable expansion of North Patagonian Rain Forest taxa in pulses centered at 14,200 and 13,000 ¹⁴C yr BP . Podocarpus nubigena expanded between 12,200 and 9800 ¹⁴C yr BP , along with increases in Misodendrum and Maytenus disticha-type between 11,000 and 9800 ¹⁴C yr BP. Paleovegetation records suggest that mean annual temperature was 6–7°C colder than at present during the coldest episodes between 20,200 and about 14,600 ¹⁴C yr BP , with twice the modern annual precipitation between 20,200 and 13,000 ¹⁴C yr BP, suggesting a northward shift and intensification of westerly stormtracks. Slight climate warming occurred between 20,200 and 15,800 ¹⁴C yr BP , interrupted by cooling events at 19,200 and 15,800 ¹⁴C yr BP . The initial warming of the last termination started at 14,600 ¹⁴C yr BP , followed by warming pulses at 14,200 and 13,000 ¹⁴C yr BP. These events brought glacial conditions to a cool-temperate climate, slightly cooler and wetter than modern climate, accounting for a total temperature recovery of ≥5°C by about 13,000 ¹⁴C yr BP . A general reversal in trend is inferred with cooling events at 12,200 and 11,000 ¹⁴C yr BP .  相似文献   

Hydrodynamical models of elliptical galaxies     

E. Moreno  P. Pi§mi§ 《Celestial Mechanics and Dynamical Astronomy》1988,45(1-3):81-82

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An objective Bayesian analysis of the change point problem     

Elías Moreno  George Casella  Antonio Garcia-Ferrer 《Stochastic Environmental Research and Risk Assessment (SERRA)》2005,19(3):191-204

The Bayesian literature on the change point problem deals with the inference of a change in the distribution of a set of time-ordered data based on a sample of fixed size. This is the so-called retrospective or off-line analysis of the change point problem. A related but different problem is that of the sequential change point detection, mainly analyzed from a frequentist viewpoint. While the former typically focuses on the estimation of the position in which the change point occurs, the latter is a testing problem which has a natural formulation as a Bayesian model selection problem. In this paper we provide such a Bayesian formulation, which generalizes previous formulations such as the well-known CUSUM stopping rule. We show that the conventional improper priors (also called non-informative, objective or default), cannot be used either for sequential detection of the change or for retrospective estimation. Then, we propose objective intrinsic prior distributions for the unknown model parameters. The normal and Poisson cases are studied in detail and examples with simulated and real data are provided.  相似文献   

Stratigraphical evidence of Late Holocene barrier breaching and extreme storms in lagoonal sediments of Ria Formosa, Algarve, Portugal     

C. Andrade  M. C. Freitas  J. Moreno  S. C. Craveiro 《Marine Geology》2004,210(1-4):339-362

Stratigraphical, sedimentological and paleoecological studies undertaken in lagoonal sediments of the Ria Formosa barrier lagoon indicate that a number of present-day aligned beaches outcropping within the marsh and detached from mainland (marsh detached beaches, MDB) represent the remnants of former ephemeral flood deltas, which established following barrier breaching induced by extreme storms from circa 1270 BC onwards. Dating of these beaches suggests that they resulted from multiple events of flooding separated both in time and space. Repeated emplacement of tidal deltas following overwash of the same location of the barrier is represented in the stratigraphical record by buried and partly overlapping marsh beaches. It is suggested that further refinement of the data presented in this paper and the extension of the stratigraphic survey to the entire lagoonal space will substantiate the usefulness of the stratigraphic record as a proxy to hindcast a time series of extreme storminess extending far beyond the instrumental and historical records.  相似文献   

Entropy Econometrics for combining regional economic forecasts: A Data-Weighted Prior Estimator     

Esteban Fernández-Vázquez  Blanca Moreno 《Journal of Geographical Systems》2017,19(4):349-370

Forecast combination has been studied in econometrics for a long time, and the literature has shown the superior performance of forecast combination over individual predictions. However, there is still controversy on which is the best procedure to specify the forecast weights. This paper explores the possibility of using a procedure based on Entropy Econometrics, which allows setting the weights for the individual forecasts as a mixture of different alternatives. In particular, we examine the ability of the Data-Weighted Prior Estimator proposed by Golan (J Econom 101(1):165–193, 2001) to combine forecasting models in a context of small sample sizes, a relative common scenario when dealing with time series for regional economies. We test the validity of the proposed approach using a simulation exercise and a real-world example that aims at predicting gross regional product growth rates for a regional economy. The forecasting performance of the Data-Weighted Prior Estimator proposed is compared with other combining methods. The simulation results indicate that in scenarios of heavily ill-conditioned datasets the approach suggested dominates other forecast combination strategies. The empirical results are consistent with the conclusions found in the numerical experiment.  相似文献   

Calbuco Volcano and minor eruptive centers distributed along the Liquiñe-Ofqui Fault Zone,Chile (41°–42° S): contrasting origin of andesitic and basaltic magma in the Southern Volcanic Zone of the Andes     

L. López-Escobar  M. A. Parada  R. Hickey-Vargas  F. A. Frey  P. D. Kempton  H. Moreno 《Contributions to Mineralogy and Petrology》1995,119(4):345-361

Calbuco volcano is a Late Pleistocene-Holocene composite stratovolcano located at 41°20 S, in the southern region of the Southern Volcanic Zone of the Andes (SSVZ; 37°–46° S). In contrast to basalt and basaltic andesite, which are the dominant lava types on the volcanic front from 37° to 42° S, Calbuco lavas are porphyritic andesites which contain a wide variety of crustal xenoliths. They have SiO₂ contents in the 55–60% range, and have comparatively low K₂O, Rb, Ba, Th and LREF abundances relative to other SSVZ centers. Incompatible element abundance ratios are similar to those of most SSVZ volcanics, but ⁸⁷Sr/⁸⁶Sr and ¹⁴³Nd/¹⁴⁴Nd are respectively higher and lower than those of adjacent volcanic centers. Basalts from nearby Osorno stratovolcano, 25 km to the northeast, are similar to other basaltic SSVZ volcanoes. However, basalts from several minor eruptive centers (MEC), located east of Calbuco and Osorno volcano along the Liquiñe-Ofqui fault zone (LOFZ), are enriched in Ba, Nb, Th and LREE, and have higher La/Yb and lower Ba/La, K/La and Rb/La. ⁸⁷Sr/⁸⁶Sr and ¹⁴³Nd/¹⁴⁴Nd in MEC basalts are respectively lower and higher than those of Osorno and Calbuco lavas. We suggest that MEC basalts were produced by lower extents of mantle melting than basalts from Osorno and other SSVZ stratovolcanoes, probably as a result of lower water content in the source of MEC basalts. Calbuco andesites formed from basaltic parents similar to Osorno basalts, by moderate pressure crystallization of a hornblende-bearing assemblage accompanied by crustal assimilation. Hornblende stability in the Calbuco andesites was promoted by the assimilation of hydrous metasedimentary crustal rocks, which are also an appropriate endmember for isotopic trends, together with magma storage at mid-crustal depths. The unique characteristics of Calbuco volcano, i.e. the stability of hornblende at andesitic SiO₂ contents, low ¹⁴³Nd/¹⁴⁴Nd and high ⁸⁷Sr/⁸⁶Sr, and abundant crustal xenoliths, provide evidence for crustal assimilation that is not apparent at more northerly volcanoes in the SSVZ.  相似文献