Prats alpins, pastura i canvi climàtic
- Autores: Laia Jarque Bascuñana
- Directores de la Tesis: Elena Albanell Trullás (dir. tes.), Jordi Bartolomé Filella (codir. tes.), Emmanuel Antonio Serrano Ferrón (codir. tes.)
- Lectura: En la Universitat Autònoma de Barcelona ( España ) en 2021
- Idioma: catalán
- Tribunal Calificador de la Tesis: Santiago Lavín González (presid.), Isabel Catalán Barrio (secret.), João L. Oliveira Carvalho (voc.)
- Programa de doctorado: Programa de Doctorado en Biodiversidad por la Universidad Autónoma de Barcelona y la Universidad de Barcelona
- Materias:
- Enlaces
- Tesis en acceso abierto en: TDX
- Resumen
Climatic and land-use changes are affecting biological systems across the globe. Alpine ecosystems, as a fragile community, are especially threatened. Grasslands from these alpine ecosystems provide environmental services like biodiversity, greenhouse gas capture and food supply for domestic and wild herbivores. Assessing the impact of different grazing intensities and a warming climate on this ecosystem may provide important information to understand, or even to predict, the implications of climatic and land-use changes on alpine ecosystems.
Here, our main goal was to assess the impact of grazing, meteorological factors and climate change on the alpine grasslands of the Eastern Pyrenees, Spain. For this purpose, Near Infrared Spectroscopy (NIRS) was assessed as an emissions-free and low-cost predictive method.
We firstly combine two approaches at different spatial scales to assess grazing impact (biomass production and nutritional value) on grasslands (study 1). On the meso-scale, results showed that heavily grazed areas with livestock and wild ungulates were more productive than less grazed areas with only wild ungulates. Based on these results, three scenarios of contrasting grazing intensities (null, high and overgrazing) were recreated on the local scale approach, to assess the impact of overgrazing on both summer above-ground biomass production and the nutritional value of plants consumed by Pyrenean Chamois. Our results confirm that grazing intensity exerted significant changes on above-ground biomass production and the protein content of grasses, but had a negligible effect on woody vegetation such as Calluna vulgaris. On the other hand, overgrazing reduced biomass production over the entire growing season but improved the nutritive values of some herbaceous plants such as Festuca sp. The worst scenario considered in production terms was under null grazing pressure, where primary production dropped.
We secondly evaluate the potential of NIRS analysis and highlighted the limitations of two methodological approaches (microhistological and NIRS analysis) used in the determination of the diet composition of herbivores (study 2). We found out that NIRS is a suitable technique only for wide taxa groups since it is accurate enough for rough diet composition studies and for long-term monitoring purposes of major plant groups. Nevertheless, NIRS technique would not be sufficient for determining the actual composition of the diet with high precision and/or at a species level.
Global climatic and land use changes impact the diet of alpine herbivores and could thus impact the performance of these species. Therefore, it is important to integrate dietary studies when assessing species’ response to global changes. In the present thesis, we have combined information from Pyrenean chamois’ diet quality and local climate to understand the effects of climate change on the diet of this herbivore (study 3). Our results indicated that local climate exerted high positive direct effect on primary production and had indirect effect on Pyrenean chamois’ diet. In such ongoing climate change, temperature is predicted to rise and snow pack is predicted to reduce. Therefore, Pyrenean chamois’ diet is predicted to improve. However, other factors than grassland production, such as the intensity of competition between animals, grassland composition and quality and foraging strategies, may affect chamois diet quality. Further studies would be necessary to assess the effect of these factors on the chamois’ diet quality.
Overall, chamois nutrient value and forage availability improve under certain grazing pressure, diet quality increases with warmer temperatures and the chamois diet can be monitored by using NIRS as a cheap, quick and reliable method. However, further studies should be carried out to describe how forage availability trend in a warming climate scenario could affect chamois population dynamics more broadly. These conclusions could be crucial to endorse profitable grazing activities and promote conservation of alpine ecosystems under a global change scenario.
