Likely effects of climate change on growth of Quercus ilex, Pinus halepensis, Pinus pinaster, Pinus sylvestris and Fagus sylvatica forests in the Mediterranean region

Mediterranean forest growth is constrained by drought and high temperatures during summer. Effects of climate change on these forests depend on how changes in water availability and temperature will take place. A process-based forest growth model, growth of trees is limited by water in the Mediterranean (GOTILWA+), was applied in the Mediterranean region on Quercus ilex, Pinus halepensis, P. pinaster, P. sylvestris and Fagus sylvatica forests. The effects of climate change on growth were analysed, as well as the effect of thinning cycle length, combined with the assumption of different soil depths. Thinning cycle lengths was included because it can affect the response of stands to climatic conditions, and soil depth because this is positively related to soil water-holding capacity and consequently may change the effects of drought. The simulation period covered 140 years (1961-2100). Model results show that leaf area index (LAI) may increase, favoured by the increase of atmospheric CO2, particularly at sites where rainfall is relatively high and climatic conditions not too warm. The predicted increase in temperature significantly influenced mean leaf life span (MLLS). MLLS of E sylvatica would increase with climate change, implying a longer growing period. Conversely, MLLS of evergreen species would be reduced, accelerating leaf turnover. In general, our results showed a higher production promoted by projected climate change in response to the increasing atmospheric CO2 concentration and rainfall in the region. Temperature increase would have different consequences for production. In F sylvatica, the longer growing period would promote higher production, particularly when water is not limiting. On the other hand, Q. ilex and Pinus species would expend more carbon in maintaining and producing leaves to replace those lost in increased turnover rate. As expected, access of roots to deeper soil results in an increased final wood yield (FWY) due to an improved water balance that promotes higher transpiration, photosynthesis and growth. In general, the shorter the harvest cycle, the larger the FWY, because of less tree mortality between harvesting events. According to our results, temperature and rainfall may constrain growth during certain periods but if rainfall increases in the future, a positive effect on growth is likely. (C) 2002 Elsevier Science B.V. All rights reserved.