Southeast Spain Research Articles

Changes in Mediterranean Coastline According to the Coastal Type and Land Cover under Climate Change: The Case of South-east Spain

Coastline changes were analyzed considering the land cover types and the analysis of the causes that have determined these changes during the past decades. Through the overlapping of aerial photographs and GIS analysis, the results showed that the land surface increased with respect to the previous stage, gaining terrain to the sea, but this increment was caused by anthropogenic processes. In fact, without human pressure, the land surface beside the coastal line would have decreased, especially on the sandy beaches and coastal dunes. Therefore, the beaches are one of the most vulnerable ecosystems and geomorphological systems due to erosion and lack of sediment supply associated with the modified river courses (i.e. by the construction of reservoirs, concrete channeling, etc.), the inner land use changes, and the effects of global warming on the sea level. Climate change studies predict specific increases in the sea level along the coast. The aim of this work is to know if anthropic activity can reverse the effects of sea level rise and coastal erosion. In fact, it has been done for decades with measures aimed to correct impacts and favour economic activity (i.e. maintaining tourism resources) and not from the environmental issues

Runoff and soil loss in biocrusts and physical crusts from the Tabernas Desert (southeast Spain) according to rainfall intensity.

Biological soil crusts (biocrusts) influence hydrological and erosive processes in drylands, and their effects increase with hypothetic successional development. Runoff and raindrops, both dependent on rain intensity, are among the main causes of erosion in these areas. However, little is known about the existence of soil loss nonlinearity in relation to rain intensity and crust types; this nonlinearity could control biocrust succession and dynamics. The assumption of biocrust types as successional stages, which allow space-for-time sampling, makes it advisable to include all the successional stages when exploring possible nonlinearity. We considered seven types of crusts, three physical and four biological. We created four rainfall intensity levels in controlled laboratory conditions: 18, 60, 120, and 240 mm/h. In all but the last, we conducted the experiments at two levels of antecedent soil moisture. Generalized Lineal Models enabled us to test for differences. These analyses confirmed previous knowledge regarding the significant effect of rainfall intensity, crust type and antecedent soil moisture and their interactions on runoff and soil loss, despite the small sample size of the sample units. For example, runoff, and particularly soil loss, decreased along succession. Moreover, some results were novel: the runoff coefficient increased only up to 120 mm/h of rain intensity. A decoupling between runoff and soil loss occurred at high intensities. Soil loss increased as rainfall intensity increased only up to 60 mm/h, and then it decreased, mainly due to physical crusts, because of the formation of a water sheet on the surface due to the incoming rainwater exceeding the drainage capacity. Although soil loss was greater in the incipient cyanobacteria than in the most developed lichen biocrust (Lepraria community), the protection provided by any biocrust against soil loss was great compared to the physical crust, and almost as strong at all rain intensities. Soil loss increased with antecedent soil moisture only in physical crusts. Biocrusts resisted the rain splash even at a rainfall intensity of 240 mm/h.

Socioeconomic and technical factors determining the adoption of hedgerows around greenhouses in southeast Spain

Socioeconomic and technical factors determining the adoption of hedgerows around greenhouses in southeast Spain

222Rn and CO2 monitoring in soil and indoor atmosphere to understand changes in the gaseous dynamics of Rull cave (Spain)

Rull cave is a karstic cave located in Vall d’Ebo (Alicante, Southeast of Spain) developed in massive Miocene conglomerates and Cretaceous limestones. Processes in soil above Rull cave and outdoor atmosphere directly influence the underground environment of the cave. Continuous and discrete monitoring of cave atmosphere and soil (from 2012 to 2022) allows to characterise the spatial distribution and temporal variations of the gaseous concentration (222Rn and CO2) and understand the relationship between the processes which occurred in the 3-component system (soil-cave-atmosphere). Besides the presence of visitors, Rull cave maintains stable values of mean temperature (16.2 °C) and relative humidity (97.6%). In an annual cycle the cave presents two different gaseous stages (stagnation and ventilation). Maximum average values of CO2 and 222Rn concentration are reached within the stagnation stage, in the warmest period of the year. On the contrary, in the ventilation stage (in the coldest months) the cave reaches the lowest concentrations in its inner atmosphere. For the study period, daily average CO2 and 222Rn concentrations are 2008 ppm and 1745 Bq/m3, respectively. Results show that the dynamics of 222Rn and CO2 in the cave air follow different patterns defined by the complex relationships between external and internal factors. Findings from this study provide substantial information about the environmental situation of the cave atmosphere in terms of air quality for visitors and workers.

Integrated Management to Address Structural Shortage: The Case of Vega Baja of the Segura River, Alicante (Southeast Spain)

The principal objective of this study is the detailed analysis of the water deficit based on the information gathered by hydrological planning in terms of both the supply of water resources from different sources (surface and groundwater natural sources, transferred from other basins and non-conventional sources based on the reuse of regenerated waters and the desalination of seawater) and the demand for water (urban, agricultural, environmental, industrial, and recreational uses). To do this, the balance between resources and demand is determined, identifying the water deficit and its repercussions, mainly in the agricultural sector. Subsequently, a series of recommendations are proposed that can contribute to the management of water resources in accordance with their origin and availability. The study focuses on the district of Vega Baja del Río Segura, which is located in Southeast Spain, specifically in the Segura River Basin of the province Alicante, and characterized by being one of the European spaces with the greatest structural shortage of water resources. The 27 municipalities, which it constitutes and are the object of analysis in this study, have a semi-arid climate with mild temperatures and scarce torrential rainfall, which generates a continuous situation of water stress and structural shortage. The management of water resources in this area is vitally important for socio-economic development and the maintenance of the natural ecosystems. According to the climate change predictions, this deficit situation is set to worsen, which will aggravate the water imbalance.

Genetic Population Flows of Southeast Spain Revealed by STR Analysis

The former Kingdom of Granada, comprising the provinces of Granada, Málaga, and Almería (GMA), was once inhabited for over 700 years (711–1492 AD) by a North African population, which influenced its creation and establishment. The genetic data on 15 autosomal short tandem repeats (STRs) in 245 unrelated donor residents were examined in order to assess any possible admixture. As the two surnames in Spain follow an inheritance similar to the Y chromosome, both surnames of all 245 unrelated individuals were queried and annotated. The Spanish Statistics Office website was consulted to determine the regions with the highest frequency of individuals born bearing each surname. Further, several heraldry and lineage pages were examined to determine the historical origin of the surnames. By AMOVA and STRUCTURE analysis, the populations of the three provinces can be treated genetically as a single population. The analysis of allele frequencies and genetic distance demonstrated that the GMA population lay in the Spanish population group but was slightly more similar to the North African populations than the remainder of the Spanish populations. In addition, the surnames of most individuals originated in Northern and Central Spain, whereas most surnames had higher frequencies in Southern Spain. These results confirm that the GMA population shows no characteristics that reflect a greater genetic influence of North African people than the rest of the populations of the Iberian Peninsula. This feature is consistent with the historical data that African inhabitants were expelled or isolated during the repopulation of the region with Spaniards from Northern Spain. The knowledge of present populations and their genetic history is essential for better statistical results in kinship analyses.

Estimation of Global Water Quality in Four Municipal Wastewater Treatment Plants over Time Based on Statistical Methods

Wastewater from urban and industrial sources can be treated and reused for crop irrigation, which can certainly help to protect aquifers from overexploitation and potential environmental risks of groundwater pollution. In fact, water reuse can also have negative effects on the environment, such as increased salinity, pollution phenomena or soil degradation, among others. Consequently, reuse of wastewater requires rigorous treatment and a very detailed analysis of different parameters, in compliance with established quality limitation standards. Therefore, this study was carried out to develop a prediction of temporal changes in water quality by introducing a wastewater quality index (WWQI) for four regional wastewater treatment plants (WWTPs) in Murcia, Southeast Spain, where a significant number of physicochemical and biological parameters are obtained in time series over the period 2019–2021. For this purpose, multivariate statistical analyses have been adopted to predict the performance of WWQI. By robust PCA of the sixteen physicochemical variables of the raw and treated wastewater, five main principal components (PCs) were extracted, which explain between 21.39% and 36.79% of the data variability. From the loadings of the PCs, the relationships between the original parameters are analyzed. The accuracy of the developed models in terms of fit to the training dataset ranged from 74.3% to 97.9%, with p-values < 0.05. The techniques incorporated in this study provided a comprehensive evaluation framework for monitoring wastewater treatment.

Cogeneration of Fresh Water and Electricity with High-Temperature Power Cycles: Comparative Assessment of Multi-Effect Distillation and Reverse Osmosis

The pressing problems of water scarcity in many parts of the planet make water desalination one of the technological solutions for guaranteeing the fresh water supply. However, desalination processes require high energy consumption, mainly provided by fossil fuels. The integration of renewable energy sources into desalination processes is a promising option for decarbonizing the desalination sector. As most water-scarce regions with access to seawater frequently have high solar irradiation levels, it seems appropriate to exploit the sun to power the desalination process. This work presents the assessment of two integrated solar power and desalination systems regarding efficiency and water production. Two desalination processes (multi-effect distillation and reverse osmosis) are studied for potential coupling with the combined cycle of a central receiver solar plant to produce electricity and freshwater. In the case of the multi-effect distillation plant, it is integrated by replacing the Rankine cycle condenser of the combined cycle. In the case of the reverse osmosis plant, it is powered by the electricity generated from the combined cycle. For this comparison, the 21st of March has been considered as the design point and Almería (in the Southeast of Spain) as the plant location. The results show that the thermal cogeneration option renders a worse outcome (thermal efficiency of 50.2% for LT-MED case) than the decoupled generation of electricity and water (thermal efficiency of 53.3% for RO case), producing 18% less fresh water than the RO configuration (3831 m3/d vs. 4640 m3/d), due to the 6% penalty in the efficiency of the Rankine power cycle in the MED configuration as a result of increasing the condensation temperature from 42.6 °C to 70 °C.

Microarthropod communities act as functional mediators of ecosystem recovery in abandoned metal(loid) mine tailings in semiarid areas

Abandoned metal(loid) mine tailings show inhospitable conditions for the establishment of above- and below-ground communities (e.g., high metal(loid) levels, organic matter and nutrient deficiency). This worsens in semiarid areas due to the harsh climate conditions. Fertility islands (vegetation patches formed by plants that spontaneously colonize the tailings) can serve as potential nucleation spots fostering beneficial plant-microbial interactions. However, less attention has been paid to the soil invertebrates living beneath these patches and their functional role. Here, we studied whether the spontaneous plant colonization of abandoned metal(loid) mine tailings led to a greater presence of soil microarthropod communities and whether this could contribute to improving ecosystem functionality. Microarthropods were extracted, taxonomically identified and subsequently assigned to different functional groups (saphrophages, omnivores, predators) in bare soils and differently vegetated patches within metalliferous mine tailings and surrounding forests in southeast Spain. Microarthropod communities were significantly different in bare soils compared with vegetated patches in mine tailings and surrounding forests. Plant colonization led to an increase in microarthropod abundance in tailing soils, especially of mites and springtails. Moreover, saprophages and omnivores, but not predators, were favored in vegetated patches. The initial microarthropod colonization was mainly linked to higher organic matter accumulation and greater microbial activity in the vegetated patches within mine tailings. Moreover, soil formation processes already initiated in the tailings were beneficial for soil biota establishment. Thus, below-ground communities created an anchorage point for plant communities by primarily starting heterotrophic activities in the vegetated patches, thereby contributing to recover ecosystem functionality.

Whole Sequencing and Detailed Analysis of SARS-CoV-2 Genomes in Southeast Spain: Identification of Recurrent Mutations in the 20E (EU1) Variant with Some Clinical Implications

During the COVID-19 pandemic caused by SARS-CoV-2, new waves have been associated with new variants and have the potential to escape vaccinations. Therefore, it is useful to conduct retrospective genomic surveillance research. Herein, we present a detailed analysis of 88 SARS-CoV-2 genomes belonging to samples taken from COVID-19 patients from October 2020 to April 2021 at the "Reina Sofía" Hospital (Murcia, Spain) focused to variant appeared later. The results at the mentioned stage show the turning point since the 20E (EU1) variant was still prevalent (71.6%), but Alpha was bursting to 14.8%. Concern mutations have been found in 5 genomes classified as 20E (EU1), which were not characteristic of this still little evolved variant. Most of those mutations are found in the spike protein, namely Δ69-70, E484K, Q675H and P681H. However, a relevant deletion in ORF1a at positions 3675-3677 was also identified. These mutations have been reported in many later SARS-CoV-2 lineages, including Omicron. Taken together, our data suggest that preferential emergence mutations could already be present in the early converging evolution. Aside from this, the molecular information has been contrasted with clinical data. Statistical analyses suggest that the correlation between age and severity criteria is significantly higher in the viral samples with more accumulated changes.

Best Practices for Training in Sustainable Greenhouse Horticulture

Consumer demands and current legislation require intensive greenhouse horticulture to be sustainable. This poses the challenge of how to teach the concept of sustainable horticulture to all professionals involved in farming. The province of Almeria, in the south-east of Spain, is one of the major horticulture greenhouse areas in Europe, and an expert panel of relevant stakeholders was invited to look into the best pedagogical practices and methods to transfer technology and knowledge, with the goal of improving the sustainability of greenhouse horticulture. A combination of an online questionnaire, a Delphi method, and desk research was, therefore, used as the strategy to collect the data and implement the research design during 2021. On-farm/business demonstrations, virtual education, and classroom education were common pedagogical methods used. On-farm/business demonstrations, participatory education, and co-learning were identified as the best pedagogical methods to use in sustainable agriculture/horticulture training. The expert panel also concluded that participatory education and co-learning should be further explored whereas virtual and classroom education should play a less dominant role in the training activities. This knowledge can help training organizations and designers to avoid common mistakes, tailor their training activities, and be mindful of common barriers and (mis)conceptions.

Development of Smart Irrigation Equipment for Soilless Crops Based on the Current Most Representative Water-Demand Sensors.

Due to the edaphoclimatic conditions in southeast Spain, which are expected to worsen due to climate change, more efficient ways of using water must be found to maintain sustainable agriculture. Due to the current high price of irrigation control systems in southern Europe, 60-80% of soilless crops are still irrigated, based on the experience of the grower or advisor. The hypothesis of this work is that the development of a low-cost, high-performance control system will allow small farmers to improve the efficiency of water use by obtaining better control of soilless crops. The objective of the present study was to design and develop a cost-effective control system for the optimization of soilless crop irrigation after evaluating the three most commonly used irrigation control systems to determine the most efficient. Based on the agronomic results comparing these methods, a prototype of a commercial smart gravimetric tray was developed. The device records the irrigation and drainage volumes and drainage pH and EC. It also offers the possibility of determining the temperature, EC, and humidity of the substrate. This new design is scalable thanks to the use of an implemented data acquisition system called SDB and the development of software in the Codesys programming environment based on function blocks and variable structures. The reduced wiring achieved by the Modbus-RTU communication protocols means the system is cost-effective even with multiple control zones. It is also compatible with any type of fertigation controller through external activation. Its design and features solve the problems in similar systems available on the market at an affordable cost. The idea is to allow farmers to increase their productivity without having to make a large outlay. The impact of this work will make it possible for small-scale farmers to have access to affordable, state-of-the-art technology for soilless irrigation management leading to a considerable improvement in productivity.

Flood impacts on vegetation and hydraulics in ephemeral channels and dynamics of recovery

Vegetation can have a particularly strong effect on hydraulics and processes in dryland, ephemeral channels, where plants often occupy the channel bed. To understand the hydraulics, feedback effects and ecological dynamics for use in modelling and management, data on flow effects and vegetation dynamics are needed. Evidence from sites in southeast Spain, monitored for decades, is analysed here in relation to an extreme flood in September 2012 to identify thresholds for damage and destruction of plants, to assess rates of recovery, and to quantify effects of varying vegetation density and height on channel hydraulics. Repeated quadrat measurements provide data on vegetation cover, health and heights of plants, and were analysed in relation to measured flow stage and cross-section topographic surveys before, after and since the 2012 flood. Much of the vegetation was destroyed in the flood event, including the dominant Retama, resetting the vegetation. Threshold levels of shear stress for mortality and removal of the plants have been calculated. Rates of recovery have varied spatially, with little regrowth in main channels or on elevated floodplains, but strong growth occurring on bars. The different degrees of vegetation cover and height are calculated to have a very large effect on the flow hydraulics. The results support the proposal that dense vegetation cover can be highly effective in channel management by slowing flow, reducing erosion and increasing sedimentation.

Plant Growth, Yield, and Fruit Size Improvements in ‘Alicia’ Papaya Multiplied by Grafting

Papaya (Carica papaya L.) is one of the few fruit crops still propagated by seeds. However, its trioecious condition and the heterozygosity of the seedlings make urgent the development of reliable vegetative propagation procedures. In this experiment, we compared, in a greenhouse sited in Almería (Southeast Spain), the performance of plantlets of 'Alicia' papaya originated by seed, grafting, and micropropagation. Our results show that grafted papayas were more productive than seedlings papayas (7% and 4% for total and commercial yield), while in vitro micropropagated papayas were the least productive (28 and 5% less in total and commercial yield than grafted papayas, respectively). Root density and dry weight were both higher in grafted papayas, while the seasonal production of good quality, well-formed, flowers was also enhanced in grafted papayas. On the contrary, micropropagated 'Alicia' plants yielded less and lighter fruit despite these in vitro plants blooming earlier and setting fruit at desirable lower trunk height. Less tall and less thick plants and reduced production of good quality flowers might explain these negative results. In addition, the root system of micropropagated papaya was more superficial, while in grafted papayas, the root system was larger and had more fine roots. Our results suggest that the cost-benefit ratio does not favor the choice of micropropagated plants unless elite genotypes are used. On the contrary, our results encourage more research on grafting, including the search for suitable rootstocks for papaya.

Interspecific facilitation favors rare species establishment and reduces performance disparities among adults

AbstractQuestionsA variety of mechanisms sustain diversity in natural communities as a result of ecological interactions between organisms. Competition has been studied extensively in the context of species maintenance, but facilitation is often conceptualized as simply reducing competition between functionally different species, which tends to decline throughout the plants' life span. Here we explore how interspecific facilitation may sustain diversity throughout the species' life by avoiding the extinction of locally rare species at juvenile stages and reducing performance disparities between neighbors of differing species at mature stages.MethodsTo do so, we measured whether rarer species relied more on facilitation than abundant ones in semiarid shrubland in southeast Spain. A mechanistic explanation of this relationship was subsequently tested by correlating rarity with the species' affinity to a particularly edaphic stressful environment. Finally, we assessed whether growing associated with neighbors in vegetation patches shaped by facilitation could balance performance disparities between species when they become adults.ResultsWe show that facilitation (i) favors the rare species, which, in addition, tend to be those with low affinity to the stressful environment, and (ii) reduces the performance dissimilarities among plants growing associated within multispecific vegetation patches compared to plants growing alone.ConclusionsThese facilitative effects, beyond the reduction of competition between functionally similar species, might ensure positive and long‐lasting effects of biotic interactions, implying a more critical role for facilitation in preserving biodiversity than previously thought.

Landslide susceptibility mapping using maximum entropy (MaxEnt) and geographically weighted logistic regression (GWLR) models in the Río Aguas catchment (Almería, SE Spain)

A landslide susceptibility analysis has been made in the Río Aguas catchment (Almeria, Southeast Spain), using two statistical models, Maximum Entropy (MaxEnt) and Geographically Weighted Logistic Regression (GWLR). For this purpose, a previous landslide inventory has been used and re-elaborated, reaching a total incidence of 2.58% of the whole area. Different types of movements have been distinguished, being rock falls, slides and complex movements the predominant. From the inventory, the centroid of the rupture zone has been extracted to represent the landslides introduced in the models. A previous factor analysis has been made, using 12 predictors related to morphometry, hydrography, geology and land cover, with 5 m grid spacing, allowing the selection of factors to be used in the analysis and discarding those showing correlation between them. Then, MaxEnt and GWLR models are applied using different distributions of training and testing samples from the landslide inventory. For the validation, the Area Under the Curve of the Receiver Operating Characteristic (AUC-ROC) has been used but additionally, the degree of fit (DF) has allowed to validate the rupture zones themselves, not only the centroids. Results show an excellent prediction with both metrics in all the methods and samples, but the better results are obtained in the GWLR method for AUC and in the MaxEnt for the degree of fit. Therefore, a consensus model of both methods has been obtained, that improves even more the results reaching an AUC value of 0.99 and a degree of fit of 90%.

Rare Recombinant GI.5[P4] Norovirus That Caused a Large Foodborne Outbreak of Gastroenteritis in a Hotel in Spain in 2021.

Noroviruses are among the most important causes of acute gastroenteritis (AGE). In summer 2021, a large outbreak of norovirus infections affecting 163 patients, including 15 norovirus-confirmed food handlers, occurred in a hotel in Murcia in southeast Spain. A rare GI.5[P4] norovirus strain was identified as the cause of the outbreak. The epidemiological investigation determined that norovirus transmission might have been initiated through an infected food handler. The food safety inspection found that some symptomatic food handlers continued working during illness. Molecular investigation with whole-genome and ORF1 sequencing provided enhanced genetic discrimination over ORF2 sequencing alone and enabled differentiation of the GI.5[P4] strains into separate subclusters, suggesting different chains of transmission. These recombinant viruses have been identified circulating globally over the last 5 years, warranting further global surveillance. IMPORTANCE Due to the large genetic diversity of noroviruses, it is important to enhance the discriminatory power of typing techniques to differentiate strains when investigating outbreaks and elucidating transmission chains. This study highlights the importance of (i) using whole-genome sequencing to ensure genetic differentiation of GI noroviruses to track chains of transmission during outbreak investigations and (ii) the adherence of symptomatic food handlers to work exclusion rules and strict hand hygiene practices. To our knowledge, this study provides the first full-length genome sequences of GI.5[P4] strains apart from the prototype strain.

Updating Active Deformation Inventory Maps in Mining Areas by Integrating InSAR and LiDAR Datasets

Slope failures, subsidence, earthworks, consolidation of waste dumps, and erosion are typical active deformation processes that pose a significant hazard in current and abandoned mining areas, given their considerable potential to produce damage and affect the population at large. This work proves the potential of exploiting space-borne InSAR and airborne LiDAR techniques, combined with data inferred through a simple slope stability geotechnical model, to obtain and update inventory maps of active deformations in mining areas. The proposed approach is illustrated by analyzing the region of Sierra de Cartagena-La Union (Murcia), a mountainous mining area in southeast Spain. Firstly, we processed Sentinel-1 InSAR imagery acquired both in ascending and descending orbits covering the period from October 2016 to November 2021. The obtained ascending and descending deformation velocities were then separately post-processed to semi-automatically generate two active deformation areas (ADA) maps by using ADATool. Subsequently, the PS-InSAR LOS displacements of the ascending and descending tracks were decomposed into vertical and east-west components. Complementarily, open-access, and non-customized LiDAR point clouds were used to analyze surface changes and movements. Furthermore, a slope stability safety factor (SF) map was obtained over the study area adopting a simple infinite slope stability model. Finally, the InSAR-derived maps, the LiDAR-derived map, and the SF map were integrated to update a previously published landslides’ inventory map and to perform a preliminary classification of the different active deformation areas with the support of optical images and a geological map. Complementarily, a level of activity index is defined to state the reliability of the detected ADA. A total of 28, 19, 5, and 12 ADAs were identified through ascending, descending, horizontal, and vertical InSAR datasets, respectively, and 58 ADAs from the LiDAR change detection map. The subsequent preliminary classification of the ADA enabled the identification of eight areas of consolidation of waste dumps, 11 zones in which earthworks were performed, three areas affected by erosion processes, 17 landslides, two mining subsidence zone, seven areas affected by compound processes, and 23 possible false positive ADAs. The results highlight the effectiveness of these two remote sensing techniques (i.e., InSAR and LiDAR) in conjunction with simple geotechnical models and with the support of orthophotos and geological information to update inventory maps of active deformation areas in mining zones.

Role of dry watercourses of an arid watershed in carbon and nitrogen processing along an agricultural impact gradient

In the Mediterranean arid region such as Southeast (SE) Spain, a considerable part of the fluvial network runs permanently dry. Here, many dry watercourses are embedded in catchments where agriculture has brought changes in carbon (C) and nitrogen (N) availability due to native riparian vegetation removal and the establishment of intensive agriculture. Despite their increasing scientific recognition and vulnerability, our knowledge about dry riverbeds biogeochemistry and environmental drivers is still limited, moreover for developing proper management plans at the whole catchment scale. We examined CO2 and N2O emissions in five riverbeds in SE Spain of variable agricultural impact under dry and simulated rewetted conditions. Sediment denitrifying capacity upon rewetting was also assessed. We found that, regardless of agricultural impact, all riverbeds can emit CO2 under dry and wet conditions. Emissions of N2O were only observed in our study when a long-term rewetting driving saturated sediments was conducted. Besides, most biogeochemical capabilities were enhanced in summer, reflecting the sensitiveness of microbial activity to temperature. Biogeochemical processing variation across rivers appeared to be more controlled by availability of sediment organic C, rather than by agriculturally derived nitrate. We found that the studied dry riverbeds, agriculturally affected or not, may be active sources of CO2 and contribute to transitory N2O emissions during rewetting phenomena, potentially through denitrification. We propose that management plans aiming to support ecosystem biogeochemistry through organic C from native vegetation rather than agricultural exudates would help to reduce anthropogenic greenhouse gases emissions and excess of nutrients in the watershed and to control the nitrate inputs to coastal ecosystems.

Factors influencing the use of rainwater for agricultural irrigation: the case of greenhouse agriculture in southeast Spain

Abstract The availability and quality of water resources for agricultural irrigation are being increasingly compromised by different factors. In this context, the installation of rainwater harvesting (RWH) systems for use in agricultural holdings can contribute to mitigating this problem. However, the use of these systems by farmers continues to be very low. This paper analyses the factors that influence a farmer's decision to adopt these systems to take advantage of rainwater. Greenhouse agriculture in southeast Spain is the case studied. For this, a binary logistic regression model based on a survey administered to farmers was used. Among the variables found to be significant, the most important variables are the quantity of water in the pond, the pond capacity and environmental awareness. The variables that least affect the adoption decision are age, education level and income. These results have allowed the development of the main lines of action for policy-makers to intervene in order to promote the adoption of these systems. These measures focus on enhancing the training of farmers, providing them with financial support and boosting their environmental awareness. The results of this study lead to improved research on farmers’ behaviour and sustainable management of water resources in agriculture.