Figueroa I., López B.C., López A., Potrony D. (2009) What happens to ptarmigan when marmots arrive?. Ethology Ecology and Evolution. 21: 251-260.EnllaçDoi: 10.1080/08927014.2009.9522480
Rock ptarmigan is a vulnerable species in the southern Pyrenees, with less than 300 pairs and two unconnected populations. Alpine marmot was introduced in the northern Pyrenees between 1955 and 1988, but they rapidly colonised the southern slopes, with an actual estimated population of around 10,000 individuals. Both species are mainly herbivores, develop their activities on the ground and have their offspring at the same time, so they may compete at various levels. We studied the possible interactions between the two species based on fleld observations, bibliographic data and Geographical Information System (GIS) analysis. We found that alpine marmot has colonised all habitats occupied by rock ptarmigan in the southern Pyrenees, but their plant diet is absolutely differentiated. We also analysed the composition of golden eagle nests and conflrmed that this predator predates the two species. From fleld observations in areas where the two species have coexisted for more than 10 years, we observed no behavioural interaction between the two species. So, although both species share space and time in the alpine communities, both diet differentiation and probably behavioural avoidance permits their coexistence.
López B.C., Figueroa I., Pino J., López A., Potrony D. (2009) Potential distribution of the alpine marmot in Southern Pyrenees. Ethology Ecology and Evolution. 21: 225-235.EnllaçDoi: 10.1080/08927014.2009.9522477
Alpine marmots were introduced in the French Pyrenees between 1948 and 1988. The exact number of re-introduced individuals is unknown, but it oscillated around 400. The likely preference of marmots for the southern sunny slopes rapidly facilitated their expansion to the southern Pyrenees, where the lack of both natural predators and of important interspeciflc competitors also likely facilitated an important expansion of this species. There is only one attempt to broadly calculate the population of marmots in the southern Pyrennes, estimating a population of around 10,000 individuals. However, there exist no reliable data to calculate the potential distribution of this new colonizing species in the southern Pyrenees, and a map of the potential distribution of the species is necessary to see whether alpine marmots can potentially establish in sites where it might be necessary to manage its populations for various reasons. We developed a map of potential distribution based on census carried out in summer of 2007 in an area of more than 600 km. We censused more around 300 colonies together with around 300 random points to characterized habitat selection variables. A map with a pixel size of 15 × 15 m has been obtained based on preferred habitats and also on distances to other habitats for the whole southeastern Pyrenees.
López B.C., Gracia C.A., Sabaté S., Keenan T. (2009) Assessing the resilience of Mediterranean holm oaks to disturbances using selective thinning. Acta Oecologica. 35: 849-854.EnllaçDoi: 10.1016/j.actao.2009.09.001
Climate change will increase the frequency and the intensity of droughts in the Mediterranean region, likely reducing growth and increasing mortality of holm oaks (Quercus ilex), one of the most abundant species of Mediterranean forests. In water-limited systems such as those of the Mediterranean, carbon allocation patterns strongly favour belowground accumulation, especially in large subterranean structures called lignotubers. The resilience of these forests depends largely on the replenishment rate of these carbon reserves after disturbances. An experimental thinning, with two intensities (removal of 40% and 80% of basal area), was performed in 1992 in a holm oak forest at the Prades Experimental Complex of Catchments (NE Spain). In 2002, a second thinning was carried out in subplots within the former experimental 0.5 ha plots. Samples from the lignotubers of holm oak trees were analyzed for starch, and both mobile and immobile chemical components, in order to assess the resilience of holm oaks to repeated disturbances. Our results show that after 10 years, starch stocks in the lignotubers have only recovered to half their former values. Removing 40% of the basal area instead of 80% is suggested to be the better managing option for this kind of forests. © 2009 Elsevier Masson SAS. All rights reserved.
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