Ecology and ecophysiology of circum-Mediterranean firs in the context of climate change

In the expected climatic change scenario (with increased temperatures and water deficits) related to greenhouse effect phenomena, questions are being raised concerning the migration of the potential range of forest specie (contraction in the south and at lower altitudes, extension towards the north and higher altitudes) and the consequences on silviculture. To answer these questions, information about climatic changes and the ecophysiology of the forest species concerned is required. In this paper the case of circum-Mediterranean firs is examined as they could be in danger in parts of their present range but could also provide valuable solutions for the replacement of other species in more northerly zones with temperate humid climates and that would not be adapted to new climatic conditions. We try to answer these questions using a simplified climatic analysis of the original ranges and knowledge about the ecology and ecophysiology of firs. In the original ranges of these species climatic data is rare and very incomplete. Under these conditions it is impossible to undertake a detailed climatological analysis. Also, taking into account the diversity and heterogeneity of the climatic descriptions made by the various authors, and so as to be able to compare the different firs species, we used an aridity index. By taking a numerical approach, this index allowed us to have a general and comparative view of the climatology of the original fir ranges in relation to drought problems, and also to simulate evolution easily and compare it with the present situations for each species. On the basis of all the different results obtained it seems that, in relation to a possible increase in drought linked to a temperature increase (except no doubt for Abies numidica and A. pinsapo), there is a great risk that the present ranges of circum-Mediterranean firs will decrease in the lowest zones of their range, but also in other zones characterized by southerly aspects and shallow soils. For Abies cephalonica and Abies cilicica, species with early bud burst, there is also the risk of a possible increase in late frost damage in addition to water stress effects. Except for A. nordmanniana and A. bornmulleriana, other species may also be concerned, but to a lesser extent. Regarding the replacement of species, which would become necessary in the case of climatic change, with the exceptions of A. nordmanniana which has already been used and of for A. nebrodensis, these firs could be an alternative to the regression of more hygrophilous species, especially in zones to the north of their present ranges.