Species and plant community reorganization in the Trans-Mexican Volcanic Belt under climate change conditions

This study analyzes six vegetation communities in relation to current climatic parameters and eight climate change scenarios along an elevation gradient extending from 2,710 m to 4,210 m in the Trans-Mexican Volcanic Belt. The projected movements of 25 plant species with the current restricted or wide altitudinal distributions were also modeled. To relate climatic parameters to the species and communities, a Precipitation/Temperature (P/T) index was used both for the current and the different climate-change scenarios. The temperatures are expected to increase by 1.1A degrees to 1.7A degrees by 2020 and by 2A degrees to 3A degrees by 2050. A decrease of 4% to 13% in the annual precipitation is expected for the 2020 horizon, and a reduction between 3% and 20% is expected for 2050. The reductions in water availability were projected for all altitude levels and plant communities. The most marked reduction was under the HADLEYA2 scenario, in which the lower limit of the altitudinal range increased from 2,710 to 3,310 m (2050 horizon) with reductions in the P/T index between 36% and 39% compared to the current climate. Most plant species tended to shift their distribution from 200 to 300 m upward in the 2020 temporal horizon scenarios. The Pinus hartwegii, Alnus jorullensis and Pinus montezumae communities would have a shorter altitudinal range as they move upward and merge with the remaining species at the higher altitudinal range. For the 2050 temporal horizon, 30% of the species, primarily those from the higher altitudinal range, would disappear because their P/T index values would be above the limit of plant survival (> 4,210 m).