Growth and frost damage variation among Pinus pseudostrobus, P. montezumae and P. hartwegii tested in Michoacán, México

To study the variation in growth traits, survival, and frost damage between four taxa, Pinus pseudostrobus typical (represented by four provenances) and its variety P. pseudostrobus var. apulcensis (two provenances), Pinus montezumae (two provenances) and Pinus hartwegii (one provenance), seeds of stands of natural distribution were obtained in the States of Michoacán, Puebla, Hidalgo and Veracruz, México. Provenances were evaluated at two field sites located in forests of the Native Indian Community of Nuevo San Juan Parangaricutiro, Michoacán, at contrasting altitudes of 2200 and 2800 m. Evaluations made when seedlings were between 15 and 27 months old, indicate that there were large differences in initial growth and in frost damage between the taxa: typical P. pseudostrobus was the species with the largest growth although also the one of the largest percentage of frost damage; P. pseudostrobus var. apulcensis shows both intermediate total height and frost damage with respect to typical variety and to P. montezumae and P. hartwegii. Height growth of P. montezumae and P. hartwegii was lower than the growth of typical P. pseudostrobus and the apulcensis variety, although they presented the lowest percentage of frost damages. In order to reforest sites at Purépecha Plateau in Michoacán, it is suggested to use typical P. pseudostrobus on sites relatively free from frost occurrence, and to use P. montezumae on sites with frost occurrence. It is not recommendable to use P. pseudostrobus var. apulcensis (susceptible to frost occurrence and not having the best growth rate) or P. hartwegii (with the lowest survival rate). P. pseudostrobus var. apulcensis is a distinguishable taxon of P. pseudostrobus, due to its growth characteristics, which support the taxonomic classification according to some authors.