Evolución del ecotono bosque-pastos subalpinos de la cabecera del río Nansa (Cantabria) y su relación con los cambios en la gestión tradicional

Abstract

Rural population decline since the mid-twentieth century entails changes in the management of traditional agricultural and livestock activities that are reflected in the dynamics and evolution of forest masses. In this sense, the analysis of the upper forest limit ecotone in the headwaters of the Nansa River, object of this work, allows to verify these transformations. To carry out the study, we analyzed the historical demographic and socioeconomic context that explains its evolution through the available statistical data; photointerpretation analyzes have been carried out on the dynamics of the upper limit of the forest in this area and and, based on the definition of sampling plots and the use of dendrochronological techniques, different structures and processes of revegetation of the area, especially arboreal for the species Betula alba var. alba and Fagus sylvatica, have been characterized, related to the presence of disturbances and the historical use of space. The results obtained share the characteristics of the Cantabrian mountain environment, showing how the changes in the dynamics of the upper limit of the forest since the mid-twentieth century, have been accompanied by the loss of population, the abandonment of the scarce agricultural space and new models and livestock management, which are reflected in different structures and patterns of regeneration within the forest masses of the upper limit.