Historical and current spatial modeling of the sacred fir (Abies religiosa [Kunth] Schltdl. & Cham.) in the Trans-Mexican Volcanic Belt

Introduction: Climatic conditions in the Trans-Mexican Volcanic Belt during the middle Holocene were different from today's conditions, which may have an effect on the historical distribution areas of the sacred fir (Abies religiosa [Kunth] Schltdl. & Cham.).  Objective: To determine whether the environmental requirements that delimit the current distribution of the sacred fir in the Trans-Mexican Volcanic Belt have changed since 6,000 years ago. Materials and methods: A. religiosa records were obtained from the Niche Toolbox platform. The WorldClim version 2.0 variables for the current (1970-2000) and middle Holocene (CNRMCM5 and MIROC_ESM models) periods were downloaded. The distribution models were generated in MaxEnt using 75 % of the data for training and 25 % for validation. The most important variables of each period were determined with the Jackknife test.  Results and discussion: The estimated sacred fir areas were similar in both periods. Approximately 86.5 % of the sacred fir distribution is found in protected natural areas of the zone. The limiting environmental variables of its distribution are: elevation, annual precipitation, summer precipitation, annual mean temperature and diurnal temperature oscillation. Nevado de Toluca and Mexico City had larger sacred fir areas (+2 658.4 ha and +20 129.7 ha, respectively) during the Middle Holocene. Annual precipitation was 80 to 224 mm higher than the current level and the temperature was 1 °C colder. Conclusion: The most important environmental variables for sacred fir distribution are similar to those reported in the literature, indicating similarity between the current and historical ecological niche of A. religiosa.