Respuesta de la vegetación leñosa de ribera a los gradientes de alteración hidrológica aguas abajo de presas. / riparian woodland responses to flow alteration gradients downstream of dams
- Autores: María Dolores Bejarano Carrión
- Directores de la Tesis: Marta González del Tánago (dir. tes.), Miguel Marchamalo (codir. tes.)
- Lectura: En la Universidad Politécnica de Madrid ( España ) en 2010
- Idioma: español
- Materias:
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- Resumen
This thesis addresses jointly hydrology and stream ecology aware of the strong two-way dependence between them, with a special emphasis on the response of woody riparian vegetation to the altered flow regime. It first explores the relationships between the physical characteristics and different flow regimes present in a large heterogeneous Mediterranean basin. Subsequently, it analyzes how the riparian ecosystem is affected by flow modifications by examining its similarities to the pre-regulation conditions with increasing downstream position and decreasing hydrologic alteration from a dam. It also looks into possible influential factors on the longitudinal process of hydrologic effects, both within the physical environment and biota. This is done by examining the changes in woody vegetation attributes after damming along two regulated river systems, one Mediterranean and the other Boreal. On the one hand, this research demonstrates that the hydrology of a catchment is the result of its physical characteristics and that this relationship is strong enough to enable predictions of the expected natural flow regime of a regulated fluvial segment solely on the basis of physical, non-flow related variables. On the other hand, this work shows that flow alterations result into important changes of the establishment patterns, composition, abundance and diversity of riparian woody species. In addition, it evidences that while pre-regulation riparian conditions are progressively achieved downstream of a dam following a concomitant reduction of the degree of hydrologic alteration when other pressures are absent (e.g. Boreal river), this longitudinal gradient of impact decrease may be hindered by other disturbances such as water extraction for irrigation (e.g. Mediterranean river) and vary depending on particular characteristics of the fluvial reach. Finally, it exposes that the response of woody vegetation to a specific hydrologic change is highly contingent upon local geomorphology; that is, the triggering or decline of distinct riparian communities results from the combination of hydrologic and geomorphic conditions.
The possibility of predicting the natural flow regime of fluvial segments from physiographic and climatic characteristics facilitates to set the environmental flow-goals for restoration projects where pre-regulation flow series are unavailable. On the other hand, improving our understanding of the extent of hydrologic alteration impacts on freshwater ecosystems supports stakeholders in assuring effective and sustainable strategies for managing rivers.
