Societal Impact Statement Crop wild relatives (CWR) are valuable sources of genetic diversity for plant breeding. However, the identification of wild untapped genetic resources (i.e., unexploited in crops) is not always straightforward. We propose a methodology to guide the identification and conservation of these resources that integrates both genetic and ecological data. This approach enabled us to identify approximately 50 exceptional wild olive tree populations throughout the species' range that should be the focus of immediate conservation. Furthermore, our methodology is adaptable and can be applied to other plants and animals facing the same problem, making it widely useful for biological conservation. Summary Crop wild relatives (CWR) tend to harbor wider ecological, genetic, and phenotypic diversity than their cultivated counterparts. The recognition of their potential has led to the development of specific conservation plans. Nonetheless, the distinctiveness and conservation urgency of CWR pools vary considerably, making case‐specific strategies necessary. Here, we use wild olive (Olea europaea L.) to develop a framework for the identification, management, and conservation of CWR that exhibit sympatry and frequent introgression with cultivated forms. This strategy employs genetic and ecological data to prioritize untapped genetic resources. We compiled the available phylogeographic data from 118 wild olive populations spanning all known cpDNA lineages and five O. europaea subspecies distributed across the Mediterranean basin, Macaronesia and Saharan Africa, and classified all populations according to their genetic diversity and dissimilarity to the cultivated gene pool. Furthermore, we used a Species Distribution Model (SDM) and an environmental Principal Component Analysis (PCA‐env) to identify oleaster (O. e. subsp. europaea var. sylvestris) accessions under extreme ecological conditions or highly vulnerable to climate change. Our analyses identified populations with unique genetic and/or ecological features, as well as areas where wild olive has high agronomic and ecological value but remains unprotected and/or its persistence is threatened by climate change. Based on these results, we highlight 53 wild olive populations in Saharan Africa, Macaronesia, and the Mediterranean basin as priority conservation targets. More broadly, the methodology outlined here provides a transferable framework for safeguarding the diversity of other CWR with available ecological and genetic data.
Mediterranean agroecosystems are vulnerable to extreme heat-stress, especially because of their low organic matter content. Organic amendments may enhance soil nutrient content and microbial resilience to heatwaves, whose frequency is increasing in Mediterranean regions. However, their effectiveness under these conditions is still unclear. We investigated the effect of composted organic amendments (olive mill pomace, biosolids and solid urban residue) and a mineral fertiliser (diammonium phosphate) on microbial carbon use efficiency (CUE) and soil biogeochemistry in two different soils, a calcareous Vertisol and a non-calcareous Inceptisol, with low P availability, subjected to extreme heat-stress. We conducted incubation experiments (20 degrees C, 30 degrees C, 40 degrees C or 50 degrees C) to monitor C-14-glucose mineralisation and to evaluate modifications in soil biochemical properties. As a result of warming, soil microorganisms exhibited thermotolerance up to 40 degrees C, with a critical shift in microbial respiration observed at 50 degrees C. Consequently, microbial CUE, which was a function of the organic amendments and soil type, significantly declined from 0.47-0.65 at 20 degrees C to 0.27-0.45 at 50 degrees C (p < 0.05), with the unamended control decreasing by 0.010 +/- 0.001 degrees C-1 (Vertisol) and 0.007 +/- 0.001 degrees C-1 (Inceptisol). Moreover, composted olive mill pomace enhanced the resistance of soils to heat stress as they produced the highest microbial CUE at 40 degrees C in the Inceptisol and 50 degrees C in both soils (0.43 +/- 0.02 Inceptisol vs. 0.45 +/- 0.02 Vertisol). Soil biogeochemistry varied with temperature and treatment, whilst available P in soils treated with diammonium phosphate was reduced with temperature in both soils, but it was increased with biosolids for all temperatures in the Inceptisol. In conclusion, organic matter-rich organic amendments (composted olive mill pomace) may enhance the resistance of Mediterranean agricultural soils subjected to extreme heat-stress events (50 degrees C).
Gully erosion is a significant threat to the sustainability of soil in Mediterranean basins. Despite its impact, there is a lack of research providing accurate regional-scale cartography of complete gully networks. This study aims to automatically map the gully network in the olive-growing landscapes of the Guadalquivir basin (Spain) using Machine Learning (ML) algorithms: Random Forest (RF), Support Vector Machine (SVM), Decision Tree (DT), and Logistic Regression (LR). We integrated these models with 17 predictive variables (including hydrotopographic, climatic, and edaphic factors) and the Gully Head Initiation (GHI) index. RF was the most suitable model, achieving an Area Under the Curve (AUC) of 0.91 and an F1-score of 0.83, and enabled the delineation of a gully network totalling 8439.05 km. Variable importance analysis revealed that flow accumulation (17.33%) and the GHI index (nearly 30%) were the primary predictors, with the Rainy Day Normal (RDN)-based formulation outperforming the maximum daily precipitation (Pmax)-based one. Spatially, countryside hill landscapes exhibited the highest gully densities (42.50 m/ha). The results demonstrate the effectiveness of combining ML with physically based indices to generate high-resolution gully cartography for soil conservation planning in Mediterranean olive groves.
Plastic contamination alters soil physical and chemical properties, threatening essential ecosystem functions such as nutrient cycling, water infiltration and soil aggregate stability. The goal of this study is to elucidate how these effects vary with soil texture and test if they could be mitigated by increasing plant species richness. We conducted a mesocosm experiment combining two soil types (clayey and sandy), four plastic treatments (conventional, biodegradable, a mixture of both and a control) and a gradient of plant species richness (2-6 species per pot) using seven ruderal species common in urban areas. We measured plant biomass, water infiltration, field capacity, aggregate stability, organic carbon, beta-glucosidase activity and combined their individual responses into an overall multifunctionality index. Conventional plastics significantly disrupted infiltration, aggregate stability and organic carbon to a larger extent than biodegradable plastics. Negative impacts were greater in clayey than in sandy soils; multifunctionality decreased by 15% when conventional plastics were added in clayey soils but slightly increased by 3% in sandy soils. Plant richness had positive effects on half of the measured functions, either directly or indirectly through plant biomass production. In sandy soils, these positive effects partly compensated for the loss of functioning caused by plastic contamination, as reflected in higher multifunctionality. In clayey soils, however, plastic contamination not only outweighed plant diversity benefits but also weakened richness-functioning relationships. The most diverse plant mixtures exhibited transgressive overyielding, indicating functional complementarity among species that enhanced resilience to plastic-induced stress. Synthesis and applications. Our findings show that the negative effects of plastic contamination on soil functioning strongly depend on soil type and can be partly alleviated by plant diversity. In sandy soils, diverse plant communities buffered functional losses under plastic stress, whereas in clayey soils the benefits of diversity were suppressed. These results highlight that ecological restoration strategies in urban environments should prioritise increasing plant diversity in sandy soils, while managing plastic contamination is crucial in clay-rich soils where biodiversity alone cannot counteract contamination impacts.
This study examines how certain innovative tourist experiences influence the perception, satisfaction and behaviour of visitors in cities with a strong heritage tourism base. Thus, the purpose of this article is to analyse the night visit, its digitalisation and its influence on tourist satisfaction and the image of the city. The authors used the partial least squares structural equation modelling (PLS-SEM) method. The research findings show the satisfaction obtained from night visits in urban tourism, the importance of digitalisation in this context, and the role of such visits in improving the city's image. Consequences can include a possible expansion of the heritage's tourist carrying capacity, changes to tourist flows, or an increase in overnight stays in the city. The results provide practical applications for the management of urban tourism, highlighting the role of the tourist experience in improving the quality of the destination and reinforcing its attractiveness. Likewise, the research contributes to the literature on tourist cities by offering practical implications. This study contributes to the existing knowledge of urban tourism by providing practical evidence on how night-time tourist experiences during heritage visits influence visitor satisfaction and destination evaluation in cities with a strong heritage dimension. There are no academic studies to examine the variables of digitisation, tourist satisfaction, and the city's image in the context of a night-time visit to a UNESCO-recognised World Heritage Site.
