El Estado de Michoacán es el primer productor de resina en el país y Pinus oocarpa Schiede ex Schltdl. es una de sus especies más importantes por la alta producción y calidad. El objetivo del presente estudio fue analizar las características dendrométricas y productivas en relación con el clima y el suelo de 30 árboles seleccionados como superiores en producción de resina en condiciones naturales en Michoacán, México. En la zona de estudio se presentan los suelos acrisol ocrico-luvisol y luvisol crómico, dos climas (A)C(w1)(w) y Aw0(w), con temperatura media de 18 °C a 22 °C, precipitación anual entre 800 mm y 1200 mm y humedad relativa predominante de 70% a 90%. El DAP de los árboles varió de entre 31.5 cm y 89.5 cm, la altura total entre 9.0 m y 27.5 m, diámetro de copa entre 5.9 m y 14.35 m, con una producción media de resina en cinco meses de 10.67 kg. Las variables que más aportaron a la producción de resina fueron el tipo de clima, altura de fuste limpio y número de caras vivas. El suelo presentó una correlación positiva con la altura de fuste limpio (r = 0.39). Los resultados sugieren que el clima semicálido subhúmedo, los suelos de tipo luvisol crómico y la temperatura, favorecen la producción de resina en P. oocarpa, por lo que podrían usarse como indicadores en la búsqueda de árboles y zonas con buena producción para esta especie.

Conservation of Abies religiosa (sacred fir) within the Monarch Butterfly Biosphere Reserve (MBBR) in Mexico requires adaptive management to cope with expected climatic change, in order to have healthy trees for Danaus plexippus overwintering sites in the future. Open pollinated seeds from fifteen A. religiosa populations were collected along an elevational gradient (2850-3550 masl; one sampled population every 50 m of elevational difference). Seedlings were evaluated in a common garden test over a period of 30 months. We found significant differences (P < 0.03) among populations in total elongation, final height, date of growth cessation, foliage, stem and total dry weight, as well as frost damage. These differences were strongly associated with the Mean Temperature of the Coldest Month (MTCM; r2= 0.6222, P = 0.0005). Seedlings originating from lower elevation populations grew more but suffered more frost damage than those from higher elevations. Populations differentiate genetically when they are separated by 364 m in elevation. Such differentiation was used to delineate three elevational/climatic zones for seed collection, with limits defined at: 2650 masl or 9.7 °C of MTCM; 3000 masl or 8.5 °C; 3350 masl or 7.3 °C; and 3700 masl or 6.1 °C. Zonification for seedling deployment aiming to match a suitable climate in year 2030 (after projections using an ensemble of 18 General Circulation Models and a Representative Concentration Pathway 6.0 watts/ m2), would have the same MTCM zone limits, but shifted 350 m upwards in elevation. This shift would exceed the highest elevations within the MBBR, necessitating the establishment of A. religiosa stands outside the MBBR, to serve as potential future overwintering sites.

In order to determine the genetic variation among populations of Pinus hartwegii along altitudinal gradients, and the possible adaptive decoupling due to climatic change, a common garden test was set up with 13 provenances collected along an altitudinal transect (3150 to 3750 masl; collection sites were every 50 m of altitudinal difference) from Pico de Tancítaro, Michoacán, west-central Mexico. The test evaluated trees aged 4.5 to 5.5 years, and contemporary and future (year 2030; six model-emission scenarios) climate variables were estimated. We found significant (P<0.005) differences among populations in total elongation, final seedling height, basal diameter, rate of elongation, dry weight of needles, branches and stem, total dry weight and first principal component. We found a significant association between population performance, expressed as first principal component values, and their climate, where the best climatic predictor was the frost free period (r2=0.90, P<0.0001). This result indicates that the patterning of genetic differentiation among populations is strongly associated with a climatic and altitudinal gradient. We propose a re-delineation of fixed climatic and altitudinal seed zoning for seed and seedling movement, based on intervals of 26 days of difference of frost free period: Zone 1, from 240 to 214 days of frost free period or 12 to 11°C or 3150 to 3350 masl; Zone 2, 214 to 188 days or 11 to 10°C or 3350 to 3550 masl; and Zone 3, 188 to 162 days or 10 to 9°C or 3550 a 3750 masl. Projecting at what altitude will occur the same frost free period values by year 2030, we suggested that populations should be shifted 400 m attitudinally upward, through a program of assisted migration, aiming to realign the populations to the climate for which they are adapted. Seedling deployment should use future (year 2030) fixed seed zones, with the same projected climatic interval values than contemporary climate, although at the following altitudinal limits: Zone 12030, from 3550 to 3750 masl; Zone 22030, 3750 to 3950 masl; and Zone 32030, 3950 to 4150 masl.