Persona:
Díaz Sierra, Rubén

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Dirección de correo electrónico
sierra@ccia.uned.es
ORCID
0000-0001-9821-8347
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Proyectos de investigación
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Díaz Sierra
Nombre de pila
Rubén
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2021 - 20242
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Autor: Rietkerk, Max × search.filters.applied.f.itemFacultad: Facultad de Ciencias ×

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Mostrando 1 - 2 de 2
  • Miniatura
    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, Max
    Increases 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
  • Miniatura
    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, Mara
    Facilitative 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.