The impact of temperature and drought on the carbon balance of forest ecosystems: the case of a beech forest in central Italy

In the Mediterranean region, climate variables are the most important factors to explain the spatial and temporal variation of primary productivity and carbon absorption of forest ecosystems. The objective of this paper is to report on the temporal variation of the annual carbon budget in a mountain forest ecosystem of Central Italy and to highlight the impact of seasonal hot spells and drought on carbon absorption and on net ecosystem productivity. The analysis of fluxes and meteorological data, in the period 1996-2012, shows clearly that warmer temperatures coupled with limiting precipitation results in a clear and significant decrease of carbon absorption. Furthermore, the measured trends show that, over the summer, the study beech forest is able to respond and acclimate to changing climatic conditions, as far as drought is not prolonged. In the 17-year study period, the year 2007 was the driest year, resulting in the lowest value of carbon absorption by the forest ecosystem; year 2012 was the second driest year and the third lowest for C-sequestration.