Nilda Sanchez

• Doctor of Engineering
• University of Salamanca

Geotechnologies, such as Global Navigation Satellite Systems (GNSS), particularly the Global Positioning System (GPS), along with remote sensing imagery, play a pivotal role in documenting topographic features and describing land covers and uses. Collar-mounted GPS devices have proven highly effective in monitoring and tracking cattle, providing hi...

BACKGROUND The common vole is an agricultural pest and population outbreaks have caused significant crop damage in the agricultural areas of the west‐central part of the Iberian Peninsula (Spain) during the last few decades. Thus, monitoring is imperative to gain a comprehensive insight on its spatiotemporal habitat colonization dynamics. This work...

BACKGROUND The common vole has invaded the agroecosystems of northwestern Spain, where outbreaks cause important crop damage and management costs. Little is yet known about the factors causing or modulating vole fluctuations. Here, we used 11 years of vole abundance monitoring data in 40 sites to study density‐dependence and weather influence on vo...

The common vole (Microtus arvalis Pallas) is considered one of the most harmful pests for agriculture in Europe, since its natural cyclical outbreaks are linked to risk situations that can lead to significant crop losses. Furthermore, it can also constitute a public health problem as a potential environmental amplifier of zoonotic diseases, some of...

The common vole (Microtus arvalis) is a cricetid rodent that invades agricultural habitats, a fact that is especially noticeable during the cyclical population outbreaks, causing serious economic damages and human health risks. Cycles occur each two to five years, but their temporal and spatial dynamics are far to be clear. The study period here co...

The estimation of crop yield is a compelling and highly relevant task in the scenario of the challenging climate change we are facing. With this aim, a reinterpretation and a simplification of the Food and Agriculture Organization (FAO) fundamentals are presented to calculate the fresh biomass of forage crops. A normalized difference vegetation ind...

The common vole (Microtus arvalis Pallas 1778) is a cricetid rodent that finds its primary habitats in meadows, field edges and alfalfa plots. However, during periods of population outbreaks, they spread out, invading and colonizing other suboptimal habitats, such as cultivated areas of cereals, legumes, rapeseed, sunflower, etc. For this reason, t...

The common vole (Microtus arvalis Pallas 1778) shows cyclical population outbreaks ranging approximately from 2 to 5 years, although temporal and spatial patterns of its behaviour remain unclear. This species is present in Castilla y León (the largest Spanish region), having detected in recent decades recurrent episodes associated with risk situati...

In agricultural production systems, common vole (Microtus arvalis Pallas) cyclical outbreaks are associated with risk situations for crops. However, the final affectation is dependent on varying parameters such as the duration of the phenomenon until population collapse, reached abundances, dispersion and colonization from the reservoir areas to cu...

Introduction Transhumance is the most ancient sheep husbandry system that optimizes the grazing resources, while adapting to the varying environmental and climatic conditions. It is key in arid or semi-arid regions, where transhumance has proven to be traditionally efficient to use the ecosystemic primary productivity. A representative example is t...

In semi-arid regions, such as the Mediterranean, seasonal changes in climate make the migration of ruminants essential for the efficient use of ecosystemic primary productivity. Transhumance is one of the oldest sheep husbandry systems which contributes to the conservation of natural biodiversity and to minimize the effects of climate change on liv...

INNOVACIÓN MUNDO GANADERO Mayo / Junio 2022 36 En los últimos años, las geotecnologías, y concretamente la monitorización por GNSS (Global Navigation Satellite System), se ha instalado en las rutinas de la ganadería extensiva, ya que permite seguir remotamente a los animales en todo momento. Yendo un paso más allá, esos datos permiten analizar los...

GPS collars are a technology that is used extensively to monitor livestock due to its versatility. In this study, the main objective was to confirm whether it can detect the circadian rhythmicity that modulates the behavior of free-grazing sheep. The Churra-breed flock that was monitored grazed an approx. 166-ha fenced area within a dehesa ecosyste...

BACKGROUND The common vole (Microtus arvalis) is a very destructive agricultural pest. Particularly in Europe, its monitoring is essential not only for adequate management and outbreak forecasting, but also for accurately determining the vole's impact on affected fields. In this study, several alternatives for estimating the damage to alfalfa field...

This paper aims to both fit and predict crop biophysical variables with a SAR image series by performing a factorial experiment and estimating time series models using a combination of forecasts. Two plots of barley grown under rainfed conditions in Spain were monitored during the growing cycle of 2015 (February to June). The dataset included nine...

Traditional knowledge about the behavior of grazing livestock is about to disappear. Shepherds well know that sheep behavior follows non-random patterns. As a novel alternative to seeking behavioral patterns, this study quantified the grazing activities of two sheep flocks of Churra breed (both in the same area but separated by 10 years) based on G...

The common vole (Microtus arvalis Pallas) is a plague with high incidence in the agricultural areas of the northwestern plateau of the Iberian Peninsula. It is a very harmful plague for the agriculture and therefore it is essential to monitor spatio-temporally both the evolution of the vole's abundance and the crop damage incidence. The aim of this...

The accurate identification of crops is essential to help environmental sustainability and support agricultural policies. This study presents the use of a Spanish radar mission, PAZ, to classify agricultural areas with a very high spatial resolution. PAZ was recently launched, and it operates at X band, joining the synthetic aperture radar (SAR) co...

The use of conventional and intensive exploitation practices, as opposed to the organic ones, has caused a loss of the ecological value in many natural ecosystems. A clear example is the dehesa ecosystem in Spain, a semi-natural system that has a great diversity of flora and fauna and in which the intensive and industrial productive systems are rep...

Spatial downscaling has recently become a crucial process in the regional application of coarse-resolution passive microwave surface soil moisture (SSM) products. Extensive gaps in auxiliary optical/thermal infrared observation data (mainly caused by cloud cover) and gaps in coarse-resolution passive microwave SSM data lead to spatiotemporal discon...

The capability of UAVs imagery to monitor and predict the evolution of several forage associations was assessed during the whole growing cycle of 2019-20. For this purpose, eight different forage associations grown in triplicate were used: vetch-barley-triticale (VBT), vetch-triticale (VT), vetch-rye (VR), vetch-oats (VO), pea-barley-triticale (PBT...

In countries where the economy relies mostly on agricultural-livestock activities, such as Argentina, droughts cause significant economic losses. Currently, the most-used drought indices by the Argentinian National Meteorological and Hydrological Services are based on field precipitation data, such as the Standardized Precipitation Index (SPI) and...

Panel data PCA Polarimetric SAR RADARSAT-2 Since the late 1970s, remote sensing techniques have been proven to be suitable for characterizing and monitoring plants and crops. In particular, synthetic aperture radar (SAR) missions contribute considerably to this prediction effort. However, the main issue when using SAR image series together with fie...

An application of the Soil Moisture Agricultural Drought Index (SMADI) at the global scale is presented. The index integrates surface soil moisture from the SMOS mission with land surface temperature (LST) and Normalized Difference Vegetation Index (NDVI) from MODIS and allows for global drought monitoring at medium spatial scales (0.05 deg).. Biwe...

Agricultural drought is one of the most critical hazards with regard to intensity, severity, frequency, spatial extension and impact on livelihoods. This is especially true for Argentina, where agricultural exports can represent up to 10% of gross domestic product (GDP), and where drought events for 2018 led to a decrease of nearly 0.5% of GDP. In...

Remote sensing soil moisture (SM) has a low spatial resolution. By contrast, to validate remote SM maps, point measurements gathered from scattered in situ stations are typically used. Therefore, a single representative SM value for the entire domain is required. The simplest approach is the arithmetic mean. Here, eight upscaling methods for in sit...

Global Navigation Satellite Systems (GNSS), such as the Global Position System (GPS), are currently used to replace the traditional pastoralism and to remotely control the movements and location of the herds. Besides, the use of this remote monitoring can benefit the understanding of grazing resource use and livestock management. In this work we in...

Se ha evaluado la base de datos de humedad del suelo generada por el modelo SIMPA (Sistema Integrado para la Modelación de la Precipitación-Aportación), única base de datos de humedad del suelo disponible en nuestro país. Las series de SIMPA se han comparado con las de la base de datos de satélite CCI (Climate Change Initiative, European Space Agen...

Se ha evaluado la base de datos de humedad del suelo generada por el modelo SIMPA (Sistema Integrado para la Modelación de la Precipitación-Aportación), única base de datos de humedad del suelo disponible en nuestro país. Las series de SIMPA se han comparado con las de la base de datos de satélite CCI (Climate Change Initiative, European Space Agen...

Many remote sensing soil moisture (SM) products have been developed with global coverage. However, most of them are derived from passive microwave observations with very coarse resolution, greatly constraining the applications at regional scales. To increase the spatial resolution, a downscaling method is developed to downscale the 36-km Soil Moist...

Land-cover monitoring is one of the core applications of remote sensing. Monitoring and mapping changes in the distribution of agricultural land covers provide a reliable source of information that helps environmental sustainability and supports agricultural policies. Synthetic Aperture Radar (SAR) can contribute considerably to this monitoring eff...

A multi-temporal field experiment was conducted within the Soil Measurement Stations Network of the University of Salamanca (REMEDHUS) in Spain in order to retrieve useful crop information. The objective of this research was to evaluate the potential of polarimetric observations for crop monitoring by exploiting a time series of 20 quad-pol RADARSA...

The increasing frequency of drought events has expanded the research interest in drought monitoring. In this regard, remote sensing is a useful tool to globally mapping the agricultural drought. While this type of drought is directly linked to the availability of root zone soil moisture (RZSM) for plants growth, current satellite soil moisture obse...

In this study, six satellite-based root zone soil moisture (RZSM) estimates from March 2015 to December 2016 were evaluated both temporally and spatially. The first two were the Soil Moisture Active Passive (SMAP) and the Soil Moisture and Ocean Salinity (SMOS) L4 RZSM products. The other four were obtained through the Soil Water Index (SWI) approa...

The low-resolution characteristic of passive microwave surface soil moisture (SSM) products greatly limits their application in many fields at regional or local scale. Aiming to overcome this limitation, a random forest (RF)-based downscaling approach was proposed in this study to disaggregate the Soil Moisture Active and Passive (SMAP) SSM product...

This study explores the use of the Soil Moisture Agricultural Drought Index (SMADI) as a global estimator of agricultural drought. Previous research presented SMADI as a novel index based on the joint use of remotely sensed datasets of land surface temperature (LST) and normalized difference vegetation index (NDVI) from the Moderate Resolution Imag...

Together with the continuous development of passive microwave surface soil moisture (SSM) products from newly launched satellites, it is necessary to perform reliable validations to assess their accuracy. With this aim, a new "bottom-up" validation approach is proposed based on the synergistic use of in situ SSM measurements from the soil moisture...

Several studies currently strive to improve the spatial resolution of coarse scale high temporal resolution global soil moisture products of SMOS, SMAP, and ASCAT. Soil texture heterogeneity is known to be one of the main sources of soil moisture spatial variability. With the recent development of high resolution maps of basic soil properties such...

In this research, the active, passive and combined Climate Change Initiative (CCI) Soil Moisture (SM) products were evaluated in comparison with in situ SM measurements from five networks in Spain that have different spatial and temporal scales, densities and environmental conditions. Three of these networks, namely Rinconada, Morille and the Soil...

During the last decade, a variety of agricultural drought indices have been developed using soil moisture (SM), or any of its surrogates, as the primary drought indicator. In this study, a comprehensive study of four innovative SM-based indices, the Soil Water Deficit Index (SWDI), the Soil Moisture Agricultural Drought Index (SMADI), the Soil Mois...

Table S1 Maximum, minimum and mean values of the variables related to grape phenolic composition. Table S2. Maximum minimum, median and mean values of the variables related to the agronomic parameters and to water status.

Background: Phenolic composition of grapes is key when making decisions about harvest date in order to assure the quality of grapes. This work aimed to study the relation between the detailed phenolic composition of grapes and agronomic parameters and hyperspectral indices, these latter measured through field radiometry techniques. Results: Good...

Earth observation satellites working on the range of the microwave frequencies allow deriving quantitative estimates of surface soil moisture (SM). The first two space missions ever launched to measure the Earth’s surface SM had L-band microwave sensors onboard: the ESA’s Soil Moisture and Ocean Salinity and NASA’s Soil Moisture Active Passive. Als...

Since its launch in 2009, the ESA’s SMOS mission is providing global soil moisture (SM) maps at ~40 km, using the first L-band microwave radiometer on space. Its spatial resolution meets the needs of global applications, but prevents the use of the data in regional or local applications, which require higher spatial resolutions (~1-10 km). SM disag...

Currently, there are several space missions capable of measuring surface soil moisture, owing to the relevance of this variable in meteorology, hydrology and agriculture. However, the Plant Available Water (PAW), which in some fields of application could be more important than the soil moisture itself, cannot be directly measured by remote sensing....

Earth Observation (EO) technology is today at a maturity level that allows deriving operational estimates of Surface Soil Moisture (SSM) from a variety of sensors; yet, such products are provided at present at a coarse spatial and/or temporal resolution, which restricts their use in local or regional scale studies and practical applications. Herein...

This work aimed to evaluate the capability of modelled vs. in situ soil moisture observations in the northwest of Spain during a period of four years (2010-2013) in order to validate the SMOS L2 product. The comparisons were performed on a set of representative stations of the Soil Moisture Measurement Stations network of the University of Salamanc...

Commission I, WG I/2 ABSTRACT: A multi-temporal/multi-sensor field experiment was conducted within the Soil Moisture Measurement Stations Network of the University of Salamanca (REMEDHUS) in Spain, in order to retrieve useful information from satellite Synthetic Aperture Radar (SAR) and upcoming Global Navigation Satellite Systems Reflectometry (GN...

Soil moisture (SM) is an important component of the Earth’s surface water balance and by extension the energy balance, regulating the land surface temperature (LST) and evapotranspiration (ET). Nowadays, there are two missions dedicated to monitoring the Earth’s surface SM using L-band radiometers: the ESA’s SMOS and the NASA’s SMAP. LST is remotel...

A synergistic fusion of the Soil Moisture and Ocean Salinity (SMOS) L2 soil moisture with the Moderate Resolution Imaging Spectroradiometer (MODIS)-derived land surface temperature (LST) and several water/vegetation indices for agricultural drought monitoring was tested. The rationale of the calculation is based on the inverse relationship between...

A synergistic fusion of the Soil Moisture and Ocean Salinity (SMOS) L2 soil moisture with the Moderate Resolution Imaging Spectroradiometer (MODIS)-derived land surface temperature (LST) and several water/vegetation indices for agricultural drought monitoring was tested. The rationale of the calculation is based on the inverse relationship between...

A multi-temporal/multi-sensor field experiment was conducted within the Soil Moisture Measurement Stations Network of the University of Salamanca (REMEDHUS) in Spain, in order to retrieve useful information from satellite Synthetic Aperture Radar (SAR) and upcoming Global Navigation Satellite Systems Reflectometry (GNSS-R) missions. The objective o...

A new index for agricultural drought monitoring is presented based on the integration of different soil/vegetation remote sensing observations. The synergistic fusion of the surface soil moisture (SSM) from the Soil Moisture and Ocean Salinity (SMOS) mission, with the Moderate Resolution Imaging Spectroradiometer (MODIS) derived land surface temper...

A validation of the new L2 and L3 soil moisture products from the Aquarius/SAC-D mission from August 2011 to June 2014 using two in situ networks in Spain was conducted. The first network, the Soil Moisture Measurement Stations Network of the University of Salamanca (REMEDHUS), is considered to be a dense network. The second network (Inforiego) cou...

While the synergy between thermal, optical, and passive microwave observations is well known for the estimation of soil moisture and vegetation parameters, the use of remote sensing sources based on the Global Navigation Satellite Systems (GNSS) remains unexplored. During an airborne campaign performed in August 2014, over an agricultural area in t...

The temporal evolution of three soil moisture datasets, which comprised remote sensing, in situ observations and modeled data, was analyzed. The study area is located in the central part of the Duero basin (Spain), where the long-term soil moisture monitoring network REMEDHUS is operating. The soil moisture time series of several representative sta...

A comprehensive spatial and temporal validation of long-term dataset of SMOS (Soil Moisture and Ocean Salinity) and Aquarius-derived soil moisture estimates was made using two in situ networks (REMEDHUS and Inforiego) within the Duero River Basin (Spain). Results from comparison with in situ show that the SMOS L2 product has better accuracy (with v...

New remote sensing techniques based on the analysis of the Earth's surface-reflected signal from the Global Navigation Satellite Systems (GNSS-Reflectometry, or GNSS-R in short) are emerging. Soil moisture and vegetation status are some of the potential parameters that could be also retrieved from these sources. However, the complex interactions be...

The Light Airborne Reflectometer for GNSS-R Observations (LARGO) is an airborne instrument designed for measuring the coherent reflectivity from different soils. In this work, an improved version of LARGO has been used in a field campaign together with other conventional remote sensing instruments. All the corrections made to the raw coherent refle...

A comparison analysis was made between the SWDI (Soil Water Deficit Index) calculated with in situ and SMOS (Soil Moisture and Ocean Salinity satellite) soil moisture series (June-2010 to December-2014), over an agricultural area in Spain. Additionally, both SWDI have been compared with two well-known agricultural drought indices, the CMI (Crop Moi...

An increasing number of permanent soil moisture measurement networks are nowadays providing the means for validating new remotely sensed soil moisture estimates such as those provided by the ESA’s Soil Moisture and Ocean Salinity (SMOS) mission. Two types of in situ measurement networks can be found: small-scale (100–10000 km2), which provide multi...

An airborne campaign was performed during August, 2014 in an agricultural area in the Duero basin (Spain) in order to appraise the synergy between very different sources of Earth Observation imagery, and very different instruments for soil moisture retrieval. During the flight, an intensive field campaign comprising soil, plant and spectral measure...

The ESA's Soil Moisture and Ocean Salinity (SMOS) mission is the first satellite devoted to measure the Earth's surface soil moisture. It has a spatial resolution of ~ 40 km and a 3-day revisit. In this paper, a downscaling algorithm is presented as a new ability to obtain multiresolution soil moisture estimates from SMOS using visible-to-infrared...

The results of an experiment conducted in Spain over the Soil Moisture Measurement Stations Network of the University of Salamanca (REMEDHUS) are presented. The observations included airborne observations from hyperspectral optical, thermal, and microwave sensors coinciding with intensive field measurements. The hyperspectral optical and thermal da...

Surface Soil Moisture (SSM) affects the soil surface energy balance and thus affects the Land Surface Temperature (LST), and viceversa. Currently, LST and SSMare remotely sensed using TIR sensors and L-band radiometers, respectively. The NASA’s Terra/Aqua missions provide full coverage of LST measurements under clear sky conditions using MODIS. The...

Field radiometry based on high spectral capacity of spectroradiometers is an alternative to the high-cost direct or destructive measurements for monitoring agricultural vegetation. Parameters related with phenology, status and physiognomy either at leaf, plant or canopy level can potentially be estimated and monitored using measurements of the refl...

Hyperspectral indices from the Compact Airborne Spectrographic Imager (CASI 550), together with land surface temperatures from the Thermal Airborne Spectrographic Imager (TASI 600) and brightness temperatures from a L-band radiometer were combined in a semi-empirical model to obtain soil moisture at very high spatial resolution (3.5 m). The airborn...

The objective of this analysis is to demonstrate the feasibility of using a composite L2 SMOS soil moisture product for determining drought conditions by taking advantage of its spatial and temporal resolution. The work investigates the potential relationships between soil moisture anomalies and two drought indices, the Standardized Precipitation I...

In this work, a soil water balanced model (SWBM-GA) is applied for simulating the behavior of soil moisture in the Duero basin. A calibration and validation was carried out at three scale levels and at different depths of the soil profile. Also, the model has been implemented in two versions, one normal and one reduced in terms of the calibration p...

The main objective of this research was to study the streamflow evolution of a representative sample of the Spanish near-natural-regime fluvial system over the last four decades of the 20th century. The focus of this study was on those headwater river basins that, not having been subject to substantial human alteration directly via the flow regime,...

An innovative downscaling approach to obtain fine-scale soil moisture estimates from 40 km SMOS observations has been developed. It optimally blends SMOS multi-angular and full-polarimetric information with MODIS visible/data into high resolution soil moisture maps. The core of the algorithm is a model that linksmicrowave/optical sensitivity to soi...

The increasing role of pushbroom cameras in large photogrammetric projects has fostered international interest in achieving a sound knowledge of this device. In addition, the classic software tools, implemented for frame cameras, need to be adapted to cope with modified aerial triangulation and self-calibration procedures. This contribution present...

The experiment presented and discussed in this paper attempts to understand the relationships between vegetation cover measurements and soil moisture estimations, to improve soil moisture calculations based on the FAO56 water balance, also known as the Kc-ET0 (crop coefficient-reference evapotranspiration) approach. The experiment provided a detail...

This paper deals with the vicarious calibration of a linear array sensor, A DS40, and the comparison and analysis with the laboratory calibration provided by the manufacturer. For this purpose, a specific test field located in the city of Avila (Spain) was designed for the two different flights performed during the 8th and 9th of April, 2010 with a...

This paper describes the relationships found between remotely sensed soil moisture, in situ observed soil moisture, and spatial distribution of soil and climatic factors. For the comparison between remote and in situ soil moisture, soil moisture map series at high resolution, obtained by applying a downscaling approach that combines Soil Moisture a...

The vegetation optical thickness (τ) from the Soil Moisture and Ocean Salinity (SMOS) L2 products is compared to some vegetation parameters estimated both at field scale and by means of an upscaling procedure through the MODIS Normalized Difference Vegetation Index (NDVI). Vegetation measurements over rainfed cereals indicated that NDVI, Leaf Area...