Center for Advanced Studies in Arid Zones

La Serena, Chile

Center for Advanced Studies in Arid Zones

La Serena, Chile
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Tracol Y.,Center for Advanced Studies in Arid Zones | Gutierrez J.R.,Center for Advanced Studies in Arid Zones | Gutierrez J.R.,University of La Serena | Gutierrez J.R.,Institute of Ecology and Biodiversity IEB | And 3 more authors.
Journal of Arid Environments | Year: 2011

In drylands, environmental conditions under shrub canopy differ from those found in open sites. We should expect that microclimate conditions under shrubs with distinct canopy architecture should also be different. Plant Area Index (PAI) of the three most abundant shrubs species (Porlieria chilensis, Adesmia bedwellii and Proustia cuneifolia) in Bosque Fray Jorge National Park, north-central Chile was measured using a Plant Canopy Analyzer. During two years (2004-2005), we recorded the Relative Humidity and Air Temperature underneath and away from the canopy of the shrubs.The three shrub species showed significant differences in PAI. Microclimate at 30 cm and 2 m above the soil in the open conditions were drier and warmer than underneath shrub canopies. Vegetation patches generate moderate microclimate conditions.Canopy structure can buffer climatic variability, contributing to high herbaceous productivity as well as shrub recruitment. Reflecting shrub architecture and observed PAI values, the lowest microclimate variations were observed under the canopies of P. chilensis, followed by P. cuneifolia and finally A. bedwellii. We bring a novel approach quantifying the Plant Area Index instead of the Plant cover and using a low cost method that integrates the distribution of leaves and may be derived from remote sensing products. © 2010 Elsevier Ltd.

Nunez J.,University of Concepción | Nunez J.,Water Center for Arid | Rivera D.,University of Concepción | Oyarzun R.,Center for Advanced Studies in Arid Zones | Arumi J.L.,University of Concepción
Journal of Hydrology | Year: 2013

This paper addresses the relationship between multitemporal variability and regime shifts in the Pacific Decadal Oscillation and El Niño Southern Oscillation, with precipitation and streamflows in Andean watersheds of the north-central region of Chile. In addition, an analysis of the effect of a regime shift displayed by annual streamflow records on their distributional properties is performed. By applying empirical fluctuation processes to monthly standardized PDO, Niño 3.4, precipitation and streamflow time series, the occurrence of a regime shift in the streamflow series, consistent with that for PDO, but highly dependent on the latitude of particular watersheds, is shown. No regime shift is detected for the precipitation time series. Using the ensemble Empirical Mode Decomposition procedure on all series, a relationship between climatic indices and hydrological variables in two main modes is determined: the former associated with a mean period of quasi 1.5-3. years related to interannual variability, and the latter with a mean period of quasi 30-35. years, related to decadal low frequency variability. Using the regional frequency analysis based on the L-moments procedure, it is found that the distributional properties of streamflow records are influenced by the phases of the PDO, with changes that affect the mean, L-CV, L-skewness and L-kurtosis in three identified homogeneous regions. The importance of incorporating low-frequency climate variability for distributional analysis and the implications of these results for water resources management and planning in north-central Chile and similar areas is discussed. © 2013 Elsevier B.V.

Munoz R.C.,University of Chile | Quintana J.,Direccion Meteorologica de Chile | Falvey M.J.,University of Chile | Rutllant J.A.,University of Chile | And 2 more authors.
Journal of Climate | Year: 2016

The climatology and recent trends of low-level coastal clouds at three sites along the northern Chilean coast (18.3°-23.4°S) are documented based upon up to 45 years of hourly observations of cloud type, coverage, and heights. Consistent with the subtropical location, cloud types are dominated by stratocumuli having greatest coverage (> 7 oktas) and smaller heights (600-750 m) during the nighttime of austral winter and spring. Meridionally, nighttime cloud fraction and cloud-base heights increase from south to north. Long-term trends in mean cloud cover are observed at all sites albeit with a seasonal modulation, with increasing (decreasing) coverage in the spring (fall). Consistent trend patterns are also observed in independent sunshine hour measurements at the same sites. Cloud heights show negative trends of about 100 m decade-1 (1995-2010), although the onset time of this tendency differs between sites. The positive cloud fraction trends during the cloudy season reported here disagree with previous studies, with discrepancies attributed to differences in datasets used or to methodological differences in data analysis. The cloud-base height tendency, together with a less rapid lowering of the subsidence inversion base height, suggests a deepening of the coastal cloud layer. While consistent with the tendency toward greater low-level cloud cover and the known cooling of the marine boundary layer in this region, these tendencies are at odds with a drying trend of the near-surface air documented here as well. Assessing whether this intriguing result is caused by physical factors or by limitations of the data demands more detailed observations, some of which are currently under way. © 2016 American Meteorological Society.

Briones-Labarca V.,University of La Serena | Briones-Labarca V.,Center for Advanced Studies in Arid Zones | Plaza-Morales M.,University of La Serena | Giovagnoli-Vicuna C.,University of La Serena | Jamett F.,University of La Serena
LWT - Food Science and Technology | Year: 2015

This study addressed the use of papaya seeds (Vasconcellea pubescens) as a source of bioactive compounds by using different types of assisted extractions such as high hydrostatic pressure (HHPE), ultrasound (UAE) and conventional (CE) extractions. The results showed that HHPE was more effective than UAE and CE in extracting bioactive compounds and had a shorter extraction time. A high correlation between the antioxidant capacity and total phenolic content indicated that phenolic compounds could be the main source of antioxidant activity in this seed. Fatty acids were identified and quantified; oleic (n-9) and linoleic (n-6) acids were the major acids in papaya seeds. Thus, HHPE and UAE provided effective methods for bio-compound extraction from Chilean papaya seeds and could have potential benefits for the cosmetic, food or pharmaceutical industries. © 2014 Elsevier Ltd.

Flores-Aqueveque V.,University of Chile | Alfaro S.,University Paris Diderot | Vargas G.,University of Chile | Rutllant J.A.,University of Chile | And 2 more authors.
Progress in Oceanography | Year: 2015

Upwelling areas play a major role in ocean biogeochemical cycles and ultimately in global climate, especially in higly productive regions as the South Eastern Pacific. This work is based on the analysis of the aeolian lithic particles accumulated in laminated sediments off Mejillones (23°S) in the eastern boundary Humboldt Current System. It proposes a high-resolution quantitative reconstruction of the upwelling-favorable southerly wind strength in the past ~250. years, comparing its variability with changes in organic carbon export/preserved changes to the sea bottom. The increase of the intensity and variability in fluxes of particles larger than 35. μm and 100. μm since the second half of the 19th century and during the 20th century confirms a general strengthening of southerly winds in the region. Spectral analysis on the complete time-series of yearly depositional fluxes indicates that sedimentary variability can be explained by a combination of interannual (ENSO) to decadal (PDO) oscillations similar to the ones yielded by the analysis of the Interdecadal Pacific Oscillation index. However, when applied separately to the lithic fluxes of the first and last centuries of the time-series, the method shows that relative to the one of the interannual mode of variability, the influence of the decadal mode has increased in the recent period.Based on the presence/absence of particles with sizes larger than 35/100. μm, each year of the time series is classified as a 'Low wind' (<6. m/s), 'Intermediate wind' (6-8. m/s), or 'Strong wind' (10 to >12. m/s) year. From the AD 1754-1820 period to the AD 1878-1998 one, the proportion of Low and Intermediate wind years decreased from 12% and 74% to 3% and 68%, respectively, whereas the proportion of strong wind years increased from 14% to 29%. For these periods the mean organic carbon also increased 22%, stating the strong relation between export/preservation productivity rate and southerly wind intensity.In the recent period (from AD 1950 on) for which the Oceanic Niño Index is available, the strong wind years (AD 1982, 1983, 1994, and 1997) correspond to large values of this index, suggesting that constructive interferences that result from the interplay between interannual and decadal oscillations modes might explain in part the reinforcement of the winds along the North Chilean coast. © 2015 Elsevier Ltd.

Garreaud R.D.,University of Chile | Rutllant J.A.,University of Chile | Rutllant J.A.,Center for Advanced Studies in Arid Zones | Munoz R.C.,University of Chile | And 4 more authors.
Atmospheric Chemistry and Physics | Year: 2011

The VAMOS Ocean-Cloud-Atmosphere-Land Study Regional Experiment (VOCALS-REx) was a major field experiment conducted in spring of 2008 off southern Peru and northern Chile, aimed at better understanding the coupled climate systems of the southeast Pacific. Because of logistical constrains, the coastal area around 30° S was not sampled during VOCALS-REx. This area not only marks the poleward edge of the subtropical stratocumulus cloud regime (thus acting as a source of transient disturbances) but is also one of the most active upwelling centers and source of surface ocean kinetic energy along the Chilean coast. To fill such an observational gap, a small, brief, but highly focused field experiment was conducted in late spring 2009 in the near-shore region around 30° S. The Chilean Upwelling Experiment (CUpEx) was endorsed by VOCALS as a regional component. CUpEx included long-term monitoring, an intensive twoweek field campaign and off-shore research flights. Our goal was to obtain an atmospheric/oceanic dataset with enough temporal and spatial coverage to be able to document (a) the mean diurnal cycles of the lower-troposphere and upper-ocean in a region of complex topography and coastline geometry, and (b) the ocean-atmosphere response to the rapid changes in coastal winds from strong, upwelling-favorable equatorward flow (southerly winds) to downwelling-favorable poleward flow (northerly winds). In this paper we describe the measurement platforms and sampling strategy, and provide an observational overview, highlighting some key mean-state and transient features. © 2011 Author(s).

Flores-Aqueveque V.,University Paris Est Creteil | Flores-Aqueveque V.,University of Chile | Alfaro S.C.,University Paris Est Creteil | Caquineau S.,French National Center for Scientific Research | And 4 more authors.
Sedimentology | Year: 2012

The analysis of the aeolian content of marine cores collected off the coast of the Atacama Desert (Mejillones Bay, Chile) suggests that marine sediments can record inter-annual to inter-decadal variations in the regional southerly winds responsible for particle entrainment at the surface of the nearby desert. However, the establishment of a simple and direct correlation between the sediment and wind records is complicated by the difference of time scales between the erosion and accumulation processes. The aim of this work is to: (i) assess the inter-annual variability of the surface winds responsible for the sand movements; and (ii) determine whether the integration over periods of several months completely smoothes the rapid changes in characteristics of the transported and deposited aeolian material. To accomplish this aim, 14years of 10m hourly wind speed, measured at the Cerro Moreno (Antofagasta) Airport between 1991 and 2003 and at the Orica Station between 2000 and 2004, were analyzed. For each year, the wind speed statistical distribution can be represented by a combination of two to three Weibull functions. Winds of the lowest Weibull mode are too weak to move the sand grains at the surface of the pampa; this is not the case for the intermediate mode and especially for the highest speed mode which are able to erode the arid surface and transport particles to the bay. In each individual year of the period of study, the highest speed mode only accounted for a limited number of strong erosion events. Quantitative analysis of the distribution of the friction velocities and of their impact on erosion using a saltation model suggests that, although all wind speeds above threshold produce erosion events, values around 0·45msec -1 contribute less to the erosion flux. This gap allows separation of the erosion events into low and high saltation modes. The correlation (r=0·997) between the importance of the third Weibull mode and the extent of higher rate saltation indicates that the inter-annual variability of the erosion at the surface of the pampa, as well as the transport of coarse particles (>100μm), are directly related to inter-annual variations in the prevalence of the strongest winds. Finally, a transport and deposition model is used to assess the possible impact of the wind inter-annual variability on the deposition flux of mineral particles in the bay. The results suggest that inter-annual differences in the wind speed distributions have a quantifiable effect on the intensity and size-distribution of this deposition flux. This observation suggests that a detailed analysis of the sediment cores collected from the bay could be used for reconstructing the inter-annual variability of past winds. © 2011 The Authors. Journal compilation © 2011 International Association of Sedimentologists.

Vasquez J.A.,Católica del Norte University | Vasquez J.A.,Center for Advanced Studies in Arid Zones | Piaget N.,Católica del Norte University | Vega J.M.A.,Católica del Norte University
Journal of Applied Phycology | Year: 2012

In Chile, management of natural resources usually starts right before its imminent collapse or after evident declination. In the northern area of the country, the fishery of brown seaweeds has an enormous social, ecological, and economical importance. More than 11,000 people depend directly or indirectly on the collection and harvesting of this resource. Ecologically, kelps constitute areas for food, reproduction, and refuge for hundreds of invertebrates and fish species. Economically, landings up to 300,000 dry tons per year represent close to US $60 million for the industry. Until 2002, the Chilean brown seaweed fishery was mainly sustained by natural mortality, where plants cast ashore were collected by artisanal fishermen. Since then, three brown seaweed species of economic importance (Lessonia nigrescens, Lessonia trabeculata, and Macrocystis pyrifera) have been intensively harvested in coastal areas between 18° and 32° S. To manage kelp populations along the northern Chilean coast, regulations have been based on the principle "how you harvest is more important than how much you harvest". This exploitation strategy has been adopted in consensus between fishermen, industries, governmental entities, and scientists. Since L. nigrescens represents more than 70% of total brown seaweed landings, this study tests the effects of L. nigrescens harvesting on the following population variables: (1) abundance, (2) distribution, (3) juvenile recruitment, (4) plant morphology, (5) frequency of reproductive plants, and (6) biodiversity of the macroinvertebrate community associated to kelp holdfasts. Our results show that, despite the enormous harvesting pressure on Lessonia density and biomass, the associated macroinvertebrate richness has been maintained, due to normal plant growth and high recruitment all year round. © 2012 Springer Science+Business Media B.V.

Vega J.M.A.,Católica del Norte University | Broitman B.R.,Católica del Norte University | Broitman B.R.,Center for Advanced Studies in Arid Zones | Vasquez J.A.,Católica del Norte University | Vasquez J.A.,Center for Advanced Studies in Arid Zones
Journal of Applied Phycology | Year: 2014

In the last decade, exploitation of Lessonia nigrescens in northern Chile has been carried out using the best practices agreed upon by consensus between fishermen, industry, government, and scientists. These practices focus on the selective harvest of sporophytes to allow the maintenance of a reproductive stock, facilitating recruitment and minimizing grazing of benthic herbivores. To improve coverage and accessibility, enforcement of administration measures along the northern coast of Chile requires ecological indicators to monitor the sustainability of Lessonia kelps. Over 2 years, density, biomass, recruitment, and size structure of Lessonia were sampled seasonally in coastal areas with different regimens of harvesting administration as follows: (1) Management Areas for Exploitation of Benthic Resources (MAEBR), (2) Open Access Areas (OAA), and (3) Marine Protected Areas without human intervention. The use of demographic parameters as ecological indicators allows discrimination between kelp beds where good harvesting practices have been applied by users (MAEBR), and areas where management recommendations have not been put in practice (OAA). The ecological indicators reinforced the concept of co-management in MAEBR as a viable harvesting administration system along the Chilean coast, and indicated a high-harvesting pressure in OAA. Moreover, together with other harvesting parameters, they could be useful to justify the application of other administration strategies, such as quotas or bans. © 2013, Springer Science+Business Media Dordrecht.

Lapazaran J.,Technical University of Madrid | Petlicki M.,Center for Advanced Studies in Arid Zones | Navarro F.,Technical University of Madrid | Machio F.,Pontifical University of Salamanca | And 3 more authors.
Polar Research | Year: 2013

Ariebreen is a small (0.37 km2)-valley glacier located in southern Spitsbergen Our ground-penetrating radar surveys of the glacier show that it is less than 30 m thick on average, with a maximum thickness of 82 m, and it appears to be entirely cold. By analysing digital terrain models of the ice surface from different dates, we determine the area and volume changes during two periods, 1936-1990 and 1990-2007. The total ice volume of the glacier has decreased by 73% during the entire period 1936-2007, which is equivalent to a mean mass balance rate of -0.61±0.17 m y-1 w.eq. The glacier thinning rate has increased markedly between the first and second periods, from -0.50±0.22 to -0.95±0.17 m y-1 w.eq.Polar Research 2013. © 2013 J. Lapazaran et al.

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