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- Detailed detection of active layer freeze–thaw dynamics using quasi-continuous electrical resistivity tomography (Deception Island, Antarctica).Publication . Farzamian, Mohammad; Vieira, Gonçalo; Santos, Fernando A. Monteiro; Tabar, Borhan Yaghoobi; Hauck, Christian; Paz, Maria Catarina; Bernardo, Ivo; Ramos, Miguel; Angel de Pablo, MiguelClimate-induced warming of permafrost soils is a global phenomenon, with regional and site-specific vari- ations which are not fully understood. In this context, a 2- D automated electrical resistivity tomography (A-ERT) sys- tem was installed for the first time in Antarctica at Decep- tion Island, associated to the existing Crater Lake site of the Circumpolar Active Layer Monitoring – South Program (CALM-S) – site. This setup aims to (i) monitor subsurface freezing and thawing processes on a daily and seasonal basis and map the spatial and temporal variability in thaw depth and to (ii) study the impact of short-lived extreme meteoro- logical events on active layer dynamics. In addition, the feasi- bility of installing and running autonomous ERT monitoring stations in remote and extreme environments such as Antarc- tica was evaluated for the first time. Measurements were re- peated at 4 h intervals during a full year, enabling the detec- tion of seasonal trends and short-lived resistivity changes re- flecting individual meteorological events. The latter is impor- tant for distinguishing between (1) long-term climatic trends and (2) the impact of anomalous seasons on the ground ther- mal regime. Our full-year dataset shows large and fast temporal resis- tivity changes during the seasonal active layer freezing and thawing and indicates that our system setup can resolve spa- tiotemporal thaw depth variability along the experimental transect at very high temporal resolution. The largest resis- tivity changes took place during the freezing season in April, when low temperatures induce an abrupt phase change in the active layer in the absence of snow cover. The seasonal thaw- ing of the active layer is associated with a slower resistivity decrease during October due to the presence of snow cover and the corresponding zero-curtain effect. Detailed investiga- tion of the daily resistivity variations reveals several periods with rapid and sharp resistivity changes of the near-surface layers due to the brief surficial refreezing of the active layer in summer or brief thawing of the active layer during win- ter as a consequence of short-lived meteorological extreme events. These results emphasize the significance of the con- tinuous A-ERT monitoring setup which enables detecting fast changes in the active layer during short-lived extreme meteorological events. Based on this first complete year-round A-ERT monitor- ing dataset on Deception Island, we believe that this sys- tem shows high potential for autonomous applications in re- mote and harsh polar environments such as Antarctica. The monitoring system can be used with larger electrode spacing to investigate greater depths, providing adequate monitoring at sites and depths where boreholes are very costly and the ecosystem is very sensitive to invasive techniques. Further applications may be the estimation of ice and water contents through petrophysical models or the calibration and valida- tion of heat transfer models between the active layer and per- mafrost.
- Abundancia y diversidad de arañas (Araneae) en olivares del distrito de Beja (Portugal) en diferentes sistemas de cultivo.Publication . Barrientos, José A.; Silva, Andreína; Patanita, M. Isabel; Benhadi-Marín, Jacinto; Melic, Antonio; Santos, Sónia A.P.Durante 2011 y 2012 se estudió la diversidad de arañas en el suelo y en las copas de ocho olivares, cuatro de manejo biológico (dos de regadio y dos de secano) y cuatro de manejo no-biológico (dos con baja densidad de árboles y dos con una densidad elevada). Se capturaron en total 5454 arañas, de las que 1611 corresponden a olivares biológicos de regadío, 1191 a olivares biológicos de secano, 1175 a olivares intensivos de baja densidad y 1477 a olivares intensivos de alta densidad. En la muestra están representadas 31 familias y 127 especies. Se analizan los resultados desde una perspectiva faunística, destacando la presencia de algunas especies, bien por ser novedades para la fauna ibérica, bien por serlo para el distrito de Beja (Portugal). En función del planteamiento metodológico, se analizan las diferencias que muestran entre sí los diferentes sistemas de cultivo. Este análisis se realiza a través de parámetros ecológicos como la abundancia de individuos y la riqueza de especies. Se destacan las diferencias entre la fauna que habita las copas y la que explota los recursos del suelo.
- Assessing soil salinity dynamics using time-lapse electromagnetic conductivity imagingPublication . Paz, Maria Catarina; Farzamian, Mohammad; Paz, Ana Marta; Castanheira, Nádia Luísa; Gonçalves, Maria Conceição; Santos, Fernando MonteiroLezíriaGrandedeVilaFrancadeXira,locatedinPortugal,isanimportantagriculturalsystemwhere soil faces the risk of salinization due to climate change, as the level and salinity of groundwater are likely to increase as a result of the rise of the sea water level and consequently of the estuary. These changes can also affect the salinity of the irrigation water which is collected upstream of the estuary. Soil salinity can be assessed over large areas by the following rationale: (1) use of electromagnetic induction (EMI) to measure the soil appar- ent electrical conductivity (ECa, mS m−1); (2) inversion of ECa to obtain electromagnetic conductivity imaging (EMCI) which provides the spatial distribution of the soil electrical conductivity (σ,mSm−1); (3) calibration process consisting of a regression between σ and the electrical conductivity of the saturated soil paste extract (ECe, dS m−1), used as a proxy for soil salinity; and (4) conversion of EMCI into salinity cross sections using the obtained calibration equation. In this study, EMI surveys and soil sampling were carried out between May 2017 and October 2018 at four locations with different salinity levels across the study area of Lezíria de Vila Franca. A previously developed regional calibration was used for predicting ECe from EMCI. Using time-lapse EMCI data, this study aims (1) to evaluate the ability of the regional calibration to predict soil salinity and (2) to perform a preliminary qualitative analysis of soil salinity dynamics in the study area. The validation analysis showed that ECe was predicted with a root mean square error (RMSE) of 3.14 dS m−1 in a range of 52.35 dS m−1, slightly overesti- mated (−1.23 dS m−1), with a strong Lin’s concordance correlation coefficient (CCC) of 0.94 and high linearity between measured and predicted data (R2 = 0.88). It was also observed that the prediction ability of the regional calibration is more influenced by spatial variability of data than temporal variability of data. Soil salinity cross sections were generated for each date and location of data collection, revealing qualitative salinity fluctuations related to the input of salts and water either through irrigation, precipitation, or level and salinity of groundwater. Time-lapse EMCI is developing into a valid methodology for evaluating the risk of soil salinization, so it can further support the evaluation and adoption of proper agricultural management strategies, especially in irrigated areas, where continuous monitoring of soil salinity dynamics is required.
- Ground penetrating radar attenuation expressions in shallow groundwater researchPublication . Paz, Maria Catarina; Alcalá, Francisco Javier; Ribeiro, LuísThe electromagnetic-wave attenuation coefficient determines the overall resolution and effective penetration depth of ground penetrating radar (GPR) surveys. Despite this relevance to the design of proper GPR surveys, the attenuation expressions are rarely used in the applied shallow groundwater research (SGR) literature. This work examines the status of the attenuation expressions in SGR. For this, 73 GPR case studies (in 47 papers), including some information concerning the attenuation variables and parameters, were selected to build a database. From these, 18 cases (in 10 papers) provided attenuation expressions and only 11 cases (in 4 papers) used those expressions. Two types of expressions were identified, physically based global ones that try to solve a broad (but not complete) range of environmental and field technical conditions, and non-global ones adapted for specific geological environments and resolution needed. The database analysis showed that both global and non-global expressions were used exclusively in low-loss media to report an attenuation range of 0.1– 21.5 dB m1 by using common antenna frequencies in the 25–900 MHz range. The range of the attenuation expressions validity in SGR is biased because no surveys in variable-loss heterogeneous media and wider antenna frequency intervals could be compiled. The attenuation database generated seeks to improve the design of GPR surveys in SGR.
- Integrated MASW and ERT Imaging for Geological Definition of an Unconfined Alluvial Aquifer Sustaining a Coastal Groundwater-Dependent Ecosystem in Southwest PortugalPublication . Paz, Maria Catarina; Alcalá, Francisco Javier; Medeiros, Ana; Martínez-Pagán, Pedro; Pérez-Cuevas, Jaruselsky; Ribeiro, LuísThis paper integrates multichannel analysis of surface waves (MASW) and time-lapse electrical resistivity tomography (ERT) to define aquifer geometry and identify transient groundwater features of the Cascalheira Stream Basin Holocene alluvial aquifer (aquifer H), which contributes to the Santo André Lagoon, part of a coastal groundwater-dependent ecosystem (GDE), located in southwest Portugal. MASW measures shear-wave velocity (VS), allowing one to obtain steady geological models of the subsurface, and ERT measures subsurface electrical resistivity (ER), being subjected to ambient changes. MASW enables disambiguation of geological structures in low ER environments, such as coastal areas. This research covered one natural year and involved one MASW campaign, four ERT campaigns, and additional geological field surveys and groundwater monitoring to assist interpretation of results. In the area, the conjugate NW–SE and NE–SW strike-slip fault systems determine compartmentalization of geological structures and subsequent accommodation space for Holocene sedimentation. MASW and ERT surveys show how the NW–SE system deepens these structures toward the coast, whereas the NE–SW system generates small horsts and grabens, being one of these occupied by aquifer H. From upstream to downstream, aquifer H thickness and width increase from 10 m to 12 m and from 140 m to 240 m, respectively. Performance of VS and ER models was satisfactory, with a normalized error of the VR and ER models in the 0.01–0.09 range, meaning that a quantitative quota of uncertainty can be segregated from the overall uncertainty of groundwater models without substantially affecting its simulations accuracy. This methodology seeks to improve the design of shallow groundwater research in GDE preservation policies.
- Processing of high-resolution temporal climate data for daily simulations of a complex agro-ecosystemPublication . Paz, Maria Catarina; Santos, Sónia A.P.; Barreira, RaquelEcosystem services, such as natural pest control, are essential tools to be incorpora ted in future agricultural methodologies. In this paper we focus on the processing of climate data series that feed to a system of computer models simulating daily inte ractions of a pest and its predator, in a dynamic landscape, the olive grove. We filled hourly climate data series and converted them to daily climate series using R langua ge. The methodology used produces acceptable climate data series for the system to run and allows to segregate specific periods of the day while maintaining daily tem poral resolution. We expect this paper can be helpful when dealing with similar data and purpose.
- Combining of MASW and GPR Imaging and Hydrogeological Surveys for the Groundwater Resource Evaluation in a Coastal Urban Area in Southern SpainPublication . Alcalá, Francisco Javier; Martínez-Pagán, Pedro; Paz, Maria Catarina; Navarro, Manuel; Pérez-Cuevas, Jaruselsky; Domingo, FranciscoThis paper conceptualizes and evaluates the groundwater resource in a coastal urban area hydrologically influenced by peri-urban irrigation agriculture. Adra town in southern Spain was the case study chosen to evaluate the groundwater resource contributed from the northern steep urban sector (NSUS) to the southern flat urban sector (SFUS), which belongs to the Adra River Delta Groundwater Body (ARDGB). The methodology included (1) geological and hydrogeological data compilation; (2) thirteen Multichannel Analysis of Surface Waves (MASW), and eight Ground Penetrating Radar (GPR) profiles to define shallow geological structures and some hydrogeological features; (3) hydrogeological surveys for aquifer hydraulic definition; (4) conceptualization of the hydrogeological functioning; and (5) the NSUS groundwater resource evaluation. All findings were integrated to prepare a 1:5000 scale hydrogeological map and cross-sections. Ten hydrogeological formations were defined, four of them (Paleozoic weathered bedrock, Pleistocene littoral facies, Holocene colluvial, and anthropogenic filling) in the NSUS contributing to the SFUS. The NSUS groundwater discharge and recharge are, respectively, around 0.28 Mm3 year−1 and 0.31 Mm3 year−1, and the actual groundwater storage is around 0.47 Mm3. The groundwater renewability is high enough to guarantee a durable small exploitation for specific current and future urban water uses which can alleviate the pressure on the ARDGB.
- Developing an Agent-Based Model for Haplodrassus rufipes (Araneae: Gnaphosidae), a Generalist Predator Species of Olive Tree Pests: Conceptual Model OutlinePublication . Barreira, Raquel; Paz, Maria Catarina; Amaro, Luís; Sousa, José Paulo; Benhadi-Marín, Jacinto; Rasko, Mykola; Silva, António Alves da; Alves, Joana; Chuhutin, Andrey; Topping, Christopher John; Santos, Sónia A.P.Olive growing has been facing major sustainability challenges due to intensification, resulting in an increased use of pesticides and fertilizers and, consequently, in the depletion of natural resources and loss of biodiversity and landscape values. This has created an urgent need to develop models for managing complex agroecosystems that integrate factors affecting food quality, sustainability and biodiversity, providing a supporting technique to understand the consequences of agricultural management for ecosystem services. We are developing an advanced agent-based simulation (ABS) applied to olive groves to model the effects of farming practices on the abundance of olive pest predators. ABS is a modeling technique where agents represent animals (predator arthropods, in our case) acting in their environment. Our model is based on an ABS system developed by Aarhus University, the ALMaSS, which comprises highly detailed farm management and spatial structures to construct dynamic landscapes where agents operate. In this work, we present the conceptual model for one of the selected species, Haplodrassus rufipes (Araneae: Gnaphosidae.
- Integrated Geophysical Methods for Shallow Aquifers Characterization and ModellingPublication . Alcalá, Francisco Javier; Paz, Maria Catarina; Martínez-Pagán, Pedro; Santos, Fernando Monteiro
- How does climate change affect soil salinity? the case study of a Mediterranean pasture with saline groundwaterPublication . Paz, A.; Castanheira, N.; Soares, P. Matos; Farzamian, M.; Paz, Maria Catarina; Gonçalves, M. C.The case study is located in an agricultural area of alluvial origin, approximately 10 km northeast of Lisbon (Portugal). The area is a peninsula surrounded by River Tejo, its estuary, and by River Sorraia. The peninsula lies 1 to 2 m above sea level, with saline groundwater arising from the estuarine tides. The soil is typically clayey and homogeneous. The future climate projections for the Mediterranean region show a decrease in precipitation, increase in mean temperature, and increase in sea water level. These conditions aggravate the processes leading to salt-affected soils (increased evapotranspiration, decrease in salt leaching during the rainy season, and increase of the groundwater salinity). This work evaluates the influence of climate change on soil salinity and water content in a rainfed spontaneous pasture, using Hydrus-1D. Three climate scenarios, comprising series of 30 years obtained with a regional climate model, were used: reference scenario (referent to 1971-2000), RCP4.5, and RCP 8.5 (both for 2011-2040). The results show an increase in the soil salinity in the RCP scenarios compared to the reference and a decrease in the mean yearly water content of the topsoil. Both effects limit the productivity of the pasture and even compromise the plants’ growth.