Persona: Díaz Sierra, Rubén
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sierra@ccia.uned.es
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0000-0001-9821-8347
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Díaz Sierra
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Rubén
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Publicación Robust metrics for quantifying and comparing resistance and recovery in experimental studies(British Ecological Society, 2025-11-28) Zhuang, Zewei; Díaz Sierra, Rubén; Chen, YuxinVarious indices have been developed to experimentally quantify resistance and recovery (two components of engineering resilience) in response to anthropogenic and natural disturbances. This diversity complicates the selection of appropriate metrics for comparing resilience across ecosystems and studies. The presence of both positive and negative disturbances further aggravates this challenge. We propose that a suitable index for quantifying resistance and recovery in experiments should satisfy four key criteria: symmetry, monotonicity, boundedness and standardization. They are inspired by methodological parallels between resilience and plant interaction quantification. Particularly, we highlight the importance of symmetry for fairly comparing the effects of disturbances with differing directional impacts. We review and compare six metrics commonly used for resilience quantification and find that none satisfies all four criteria. Specifically, the popular index of log-transformed response ratio violates both boundedness and symmetry, making it sensitive to outliers and inappropriate for comparing increases vs. decreases induced by disturbances. By further evaluating six metrics developed for plant interaction quantification, we identify one metric (NIntA)—commonly used in that field but not in resilience research—that meets all four criteria. Synthesis and applications. We propose these four criteria as guidelines for developing and selecting appropriate metrics to quantify and compare resistance and recovery in experiments. We recommend the identified standardized index of resistance and recovery (NIntA), as it enables fair and generalizable comparisons of the effects of both positive and negative disturbances across studies and ecosystems. Furthermore, this metric can support more robust predictions of tipping point's risks and restoration outcomes.Publicación Fire Responses Shape Plant Communities in a Minimal Model for Fire Ecosystems across the World(The University of Chicago Press, 2023-09-01) Magnani, Marta; Díaz Sierra, Rubén; Sweeney, Luke; Provenzale, Antonello; Baudena, MaraAcross plant communities worldwide, fire regimes reflect a combination of climatic factors and plant characteristics. To shed new light on the complex relationships between plant characteristics and fire regimes, we developed a new conceptual mechanistic model that includes plant competition, stochastic fires, and fire-vegetation feedback. Considering a single standing plant functional type, we observed that highly flammable and slowly colonizing plants can persist only when they have a strong fire response, while fast colonizing and less flammable plants can display a larger range of fire responses. At the community level, the fire response of the strongest competitor determines the existence of alternative ecological states (i.e., different plant communities) under the same environmental conditions. Specifically, when the strongest competitor had a very strong fire response, such as in Mediterranean forests, only one ecological state could be achieved. Conversely, when the strongest competitor was poorly fire adapted, alternative ecological states emerged—for example, between tropical humid savannas and forests or between different types of boreal forests. These findings underline the importance of including the plant fire response when modeling fire ecosystems, for example, to predict the vegetation response to invasive species or to climate change.Publicación Species traits interact with stress level to determine intraspecific facilitation and competition(WILEY, 2022-07-31) Sarneel, Judith M.; Hefting, Mariet M.; Visser, Eric J. W.; Díaz Sierra, Rubén; Voesenek, Laurentius A. C. J.; Kowalchuk, George A.Questions Flooding and drought stress are expected to increase significantly across the world and plant responses to these abiotic changes may be mediated by plant–plant interactions. Stress tolerance and recovery often require a biomass investment that may have consequences for these plant–plant interactions. Therefore, we questioned whether phenotypic plasticity in response to flooding and drought affected the balance between competition and facilitation for species with specific adaptations to drought or flooding. Location Utrecht University. Methods Stem elongation, root porosity, root:shoot ratio and biomass production were measured for six species during drought, well-drained and submerged conditions when grown alone or together with conspecifics. We quantified competition and facilitation as the ‘neighbour intensity effect’ directly after the 10-day treatment and again after a seven-day recovery period in well-drained conditions. Results Water stress, planting density and species identity interactively affected standardized stem elongation in a way that could lead to facilitation during submergence for species that preferably grow in wet soils. Root porosity was affected by the interaction between neighbour presence and time-step. Plant traits were only slightly affected during drought. The calculated neighbour interaction effect indicated facilitation for wetland species during submerged conditions and, after a period to recover from flooding, for species that prefer dry habitats. Conclusions Our results imply that changing plant–plant interactions in response to submergence and to a lesser extent to drought should be considered when predicting vegetation dynamics due to changing hydroclimatic regimes. Moreover, facilitation during a recovery period may enable species maladapted to flooding to persist.Publicación Facilitation and competition deconstructed: a mechanistic modelling approach to the stress gradient hypothesis applied to drylands(Nature Research, 2024-01-25) Díaz Sierra, Rubén; Rietkerk, Max; Verwijmeren, Mart; Baudena, MaraFacilitative interactions among species are key in plant communities. While experimental tests support the Stress Gradient Hypothesis (SGH) as an association between facilitation and stress, whether the shape of net effects along stress gradients can be predicted is controversial, with no available mathematical modelling approaches. We proposed a novel test, using a modification of the R* model to study how negative and positive partial effects of plant interactions in drylands combine along two common stress gradients. We modelled different interactions: competition for water and light, amelioration of soil infiltration and/or grazing protection, obtaining that intensity and importance of facilitation did not generally increase along stress gradients, being dependent on the interaction type. While along the water stress gradient net interactions became more positive, reaching a maximum and then waning again, various outcomes were observed along the grazing gradient. Shape variety was mainly driven by the various shapes of the partial positive effects. Under resource stress, additive interaction effects can be expected, whereas when including grazing, the effects were non-additive. In the context of the SGH, deconstructing the effect of positive and negative interaction in a pairwise mechanistic models of drylands does not show a unique shape along stress gradients.Publicación Colaboraciones en Ciencias de la Naturaleza: La contaminación lumínica: efectos, retos y soluciones(Universidad Nacional de Educación a Distancia (España). Facultad de Ciencias, 2015-01-01) Enríquez de Salamanca, Álvaro; Monreal Bueno, José Ignacio; Díaz Sierra, Rubén; Martín Aranda, Rosa MaríaPublicación Modeling fuel moisture dynamics under climate change in Spain’s forests(Springer, 2023-10-27) Balaguer Romano, Rodrigo; Díaz Sierra, Rubén; Cáceres, Miquel De; Voltas, Jordi; Boer, Matthias M.; Resco de Dios, VíctorBackground Current assessments of the effects of climate change on future wildfire risk are based on either empirical approaches or fire weather indices. No study has yet used process-based models over national scales to understand how and where will increases in climate aridity affect the likelihood of fire activity through changes in the moisture content of live (LFMC) and of dead (DFMC) fuels. Here, we used process-based models to forecast changes in LFMC and DFMC under the 21st century climatic conditions projected from moderate and high greenhouse gas emission scenarios (RCP4.5 and RCP8.5). Predictions were performed across broad productivity gradients in peninsular Spain to understand how productivity mediates the effects of climate change on fuel moisture dynamics. Results LFMC and DFMC were predicted to decline under the climatic conditions projected for the coming decades. Increases in the annual frequency of days with fuel moisture content below wildfire occurrence thresholds were predicted to extend fire season lengths by 20 days under RCP4.5 and by 50 days under RCP8.5. The effects of climate change on LFMC and DFMC varied linearly and negatively with productivity (stronger fuel moisture decreases in least productive environments). Although we observed a significant mitigation effect from rising CO2 (via increases in water-use efficiency), it was not enough to offset LFMC declining trends induced by increased temperature and aridity. Conclusions We predicted that the warmer and more arid climatic conditions projected for the 21st century will lead to generalized declines in fuel moisture, lengthening fire seasons, and increasing wildfire danger. The use of process-based models to forecast LFMC dynamics allowed the consideration of plant species capabilities to buffer climate change impacts. Significant increases in the fire season length predicted in the most productive environments, currently with large fire return intervals, would pose an increase of fire danger in major Spanish carbon sinks. Finally, the CO2 mitigation effect would not be enough to offset climate change-driven declines in seasonal LFMC levels.Publicación Intra-seasonal rainfall variability and herbivory affect the interaction outcome of two dryland plant species(Ecological Society of America (ESA), 2021-04-23) Verwijmeren, M.; Baudena, M.; Wassen, M.; Díaz Sierra, Rubén; Smit, C.; Rietkerk, MaxIncreases in drought frequency in combination with overgrazing may result in degradation of (semi-) arid ecosystems. Facilitative interactions between plants are a key mechanism in preventing degradation, but it is poorly understood how they respond to increased stress by combined drought and herbivory. In this study, we used an ecohydrological model, to simulate the plant growth of two plant species interacting with each other under different rainfall and herbivory pressure scenarios. The functional traits of the two modeled plants were based on a prior field experiment in southeastern Spain, in which an unpalatable “nurse” species protected a palatable protégé species from herbivory. Moreover, the nurse species was more drought-resistant; that is, it had a lower wilting point, whereas the protégé species had a higher optimal growth rate. Firstly, we investigated the coexistence of the two plant species growing under a single limiting resource, focusing on the effect of intra-seasonal rainfall variability. We found that longer periods without rainfall within the wet season resulted in stable coexistence, whereas nearly constant rainfall led to competitive exclusion of the protégé by the nurse species. Secondly, we investigated how plant interactions varied along our studied gradients. Using the neighbor effect intensity and importance indices, we found that competitive effects increased with more constant rainfall. Moreover, higher herbivory rates resulted in increased facilitative effects of the nurse on the protégé species, but facilitative effects could only prevail over competitive effects under currently observed or higher intra-seasonal rainfall variability. This study highlights the relevance of intra-seasonal rainfall variability in explaining coexistence of species in dryland ecosystems and shows that increasing intra-seasonal rainfall variability or herbivory pressure can result in more facilitative effects from a nurse species. This information is crucial to obtain a better insight into the long-term coexistence of species, and the resulting stability of dryland ecosystems in response to future climate change