The functional response of mediterranean mountain ecosystems to herbivore pressure
- Autores: Miguel Ibáñez Álvarez
- Directores de la Tesis: Emmanuel Antonio Serrano Ferrón (dir. tes.), Jordi Bartolomé Filella (codir. tes.), Elena Baraza Ruíz (codir. tes.)
- Lectura: En la Universitat Autònoma de Barcelona ( España ) en 2022
- Idioma: inglés
- Tribunal Calificador de la Tesis: Jorge Cassinello Roldán (presid.), Juan Manuel Mancilla Leytón (secret.), Isabel Catalán Barrio (voc.)
- Programa de doctorado: Programa de Doctorado en Producción Animal por la Universidad Autónoma de Barcelona
- Materias:
- Enlaces
- Tesis en acceso abierto en: TDX
- Resumen
A long history of human presence has shaped Mediterranean mountain landscapes. Grazing has historically been a primary factor shaping forest lands. Nowadays, herds of domestic herbivores turned into feral livestock have also influenced ecosystem services in the Mediterranean.
The extent of ecosystem response to herbivore control measures is not well known in heterogeneous environments transformed by centuries of human activity and is highly dependent on environmental variables.
Chapter 1 examines the effect of excluding the activity of the feral goats (Capra aegagrus hircus) in five independent sites in the mountains of Mallorca on the soil's physical, chemical, and biological characteristics. Microbial activity increased significantly when exclusion occurred. However, all other physical and chemical measurements of the soils did not vary significantly. A multi-level meta-analysis confirms the notion that ungulate effects are context-dependent, and soil heterogeneity makes it difficult to identify clear patterns. The study results suggest that environmental context persistently drives ground response more than browsing itself, even at very small scales (< 10m).
Often is not possible to evaluate the herbivore population control management effects on the ecosystem due to the lack of information both before and after management. Furthermore, the cost and complexity of sampling in the Mediterranean mountains make regular monitoring more difficult. In Chapter 2, this problem is addressed using a remote sensing approach. Twenty-one years of time series of monthly NDVI (proxy of photosynthetic activity) data was obtained from satellite images to evaluate the effects of eradicating the black rat (Rattus rattus) on the productivity of the Mediterranean vegetation in the islet of Sa Dragonera. At the time of eradication, the rat population density was among the highest reported in an insular context. The black rat feeds mainly on seeds, shoots and leaves of woody vegetation. Therefore it is hypothesised that primary production would have increased over nine years after the rodenticide campaign. The results suggest that the current passive restoration scheme imposed after eradication is insufficient to observe effective improvement in vegetation vigour and plant recruitment capacity.
A higher spatial resolution is increasingly required in conservation management programs worldwide to study plant-herbivores interaction. To this end, chapter 3 presents a novel remote sensing approach that uses images obtained with a low-cost Unmanaged Aerial System (UAS). The study was conducted in a fenced enclosure with a captive Iberian ibex (Capra pyrenaica) population in the Ports de Tortosa-Beceit Natural Park in Tarragona. As a result, it was possible to map the resources of herbivores classified according to dietary preferences with an error of 11.8%.
In addition to representing a significant scientific contribution towards a better understanding of the functional response of Mediterranean mountain ecosystems to herbivore control, the results of this thesis represent a contribution to the management of herbivore pressure in these ecosystems. The different approaches used show that remote sensing techniques combined with field data allow for large-scale analysis that helps decision-making on an ecosystem and local scale.
