Efectos de los cambios en la ocupación del suelo en ríos de montaña: un enfoque multinivel
- Autores: Edurne Estévez
- Directores de la Tesis: José Barquín Ortiz (dir. tes.)
- Lectura: En la Universidad de Cantabria ( España ) en 2019
- Idioma: español
- Tribunal Calificador de la Tesis: Araceli Puente Trueba (presid.), Núria Catalán García (secret.), Eoin O'Gorman (voc.)
- Programa de doctorado: Programa de Doctorado en Ingeniería de Costas, Hidrobiología y Gestión de Sistemas Acuáticos por la Universidad de Cantabria
- Materias:
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- Resumen
Land use-land cover changes, in concert with climate change, are the most extensive and influential human impacts on fluvial ecosystems. This thesis aims to characterize the effects of land cover change, on mountain stream energy flow pathways, food web size structure and composition and ecosystem multifunctionality through the alteration of the basal food resources that constitute the sustenance of stream food webs and physical and chemical fluvial components. The results obtained from this multi-level approach will be highly valuable to design management solutions for mitigating the effects of land cover change and conserve headwater stream ecosystem functioning and service provision.
Forest cover determined the food resource type and quantity in the studied streams. Forested streams were characterized by a lower proportion of autochthonous food resources such as biofilm and macro-algae, and a higher proportion of allochthonous food resources such as leaf litter. Dissolved organic matter (DOM) properties also reflected gradients of forest cover in the riparian area as more oxygenated and slightly more aromatic terrestrial DOM reached the streams in more forested catchments. Nevertheless, no effect of historic land cover on DOM composition was detected.
Variations in forest cover, through the alteration of food resources, had strong effects on macroinvertebrate communities. In forested streams, macroinvertebrate communities were sustained mainly by allochthonous resources, while streams flowing through grassland/shrub landscapes were sustained mostly by autochthonous resources. However, detritivores showed a fixed assimilation of allochthonous resources independent of resource quantity, while omnivore assimilation was determined by the dominant food resource. This different behaviour between feeding groups was ultimately reflected in food web structure as community biomass was more equally distributed among the organisms composing the food webs in more forested streams. Furthermore, macroinvertebrate communities adjusted their size structure to variations in forest cover. Macroinvertebrate communities showed an internal compensatory regulation of the community size structure by means of detritivore-omnivore substitution for the maintenance of the trophic transfer efficiency, only adjusting its carrying capacity to total food resource quantity through variations in macroinvertebrate abundance.
The degree of forest cover also determined the ecosystem multifunctionality. Forest cover controlled ecosystem functioning predominantly through abiotic factors (minimum water temperature in the case of wood decomposition and light availability in the case of biofilm growth, gross primary production and ecosystem respiration), which outweighed the influence of biotic factors. Thus, variations in forest cover resulted in a change of more than 50% of the ecosystem multifunctionality. Since forest cover showed a strong interaction with catchment size, this variation in ecosystem multifunctionality was the result of the increase in wood decomposition and the decline in primary production with forest cover and the increase in biofilm growth and primary production with catchment size.
