Influencia del cambio climático en la evolución de la vegetación nival de las montañas mediterráneas. Sierra de Guadarrama, España

Abstract

It studies recent climate variation and its consequences on the nival vegetation distributionin two basins of the Sierra de Guadarrama, Spain. The climate change was documented from eighteen different variables related to temperature, pluvial and snow precipitation, snow du ration within the period 1951-2000. To evaluate vegetation response to climate variation we determined the nival correlation of the distinct vegetation classes. To do this, we considered their spatial and / or temporal relation with distinct variables of climate, snow variation, and nival geoforms. Nival vegetation maps were made of five dates (1956 to 1998) and to quan tify and explain tendencies it was necessary to calculate surfaces and percentages of change, annual mean transformation index (ITMA’s) and transition matrixes. The results show that in the area studied there are 14 vegetation classes belonging to four groups of high, medium, low and negative nival correlation. Evolution of the last fifty years is summarized in a notable spatial reduction of vegetation with high nival correlation, moderate vegetation reduction with medium nival correlation and significant vegetation expansion with negative nival correlation. Change processes leave a main succession that consists on the herbal formation substitution highly correlated with snow duration and the abundance of fusion water, by leguminous shrubsapart from the nival influence, which slowly densify.