The establishment of clonal seed orchards is a viable option for the continuous production of improved seed of desired genotypes. Grafting is the main technique used to establish clonal seed orchards. The objective of this study was to examine how the geographic location and the age class of the donor trees of buds, the phenological status of the buds, and the anatomical characteristics of the scions and the rootstocks affect the survival and growth of Pinus engelmannii Carr. grafts. Scions were collected from two trees in each of three age classes (young, middle-aged, and old). Grafting was performed with buds in two physiological states (end of dormancy and beginning of sprouting). Cross-sections of the grafted organs were obtained for anatomical analysis. A Cox proportional hazards model was used to determine the effects of the variables that were considered. The age class of the scion donor trees, the total area of the cut surface of the scion, and the density of resin channels in the scions significantly affected (p < 0.05) survival of the grafts. By contrast, the physiological state of the buds and the other anatomical characteristics of the grafted organs did not significantly affect graft survival. In P. engelmannii, grafting was most effective when scions from middle-aged trees were used. Graft survival was enhanced by a small total area of the cut surface of the scion and low density of resin channels in the scions. The area of the cambium of the scions directly influenced growth of the grafts.

Developing methods for successfully grafting forest species will be helpful for establishing asexual seed orchards and increasing the success of forest genetic improvement programs in Mexico. In this study we investigated the effects of two grafting techniques (side veneer and top cleft) and two phenological stages of the scion buds (end of latency and beginning of sprouting), in combination with other seven grafting variables, on the sprouting and survival of 120 intraspecific grafts of Pinus engelmannii Carr. The scions used for grafting were taken from a 5.5-year-old commercial forest plantation. The first grafting was performed on January 18 (buds at the end of dormancy) and the second on February 21 (buds at the beginning of sprouting). The data were examined by analysis of variance and a test of means and were fitted to two survival models (the Weibull’s accelerated failure time and the Cox’s proportional hazards model) and the respective hazard ratios were calculated. Survival was higher in the top cleft grafts made with buds at the end of latency, with 80% sprouting and an estimated average survival time of between 164 and 457 days after the end of the 6-month evaluation period. Four variables (grafting technique, phenological stage of the scion buds, scion diameter and rootstock height) significantly affected the risk of graft death in both survival models. Use of top cleft grafts with buds at the end of the latency stage, combined with scion diameters smaller than 11.4 mm and rootstock heights greater than 58.5 cm, was associated with a lower risk of death.

A seed zone or provenance region is an area within which plants can be moved with little risk of maladaptation because of the low environmental variation. Delineation of seed zones is of great importance for commercial plantations and reforestation and restoration programs. In this study, we used AFLP markers associated with environmental variation for locating and delimiting seed zones for two widespread and economically important Mexican pine species (Pinus arizonica Engelm. and P. durangensis Martínez), both based on recent climate conditions and under a predicted climate scenario for 2030 (Representative Concentration Pathway of ~4.5 Wm⁻²). We expected to observe: (i) associations between seed zones and local climate, soil and geographical factors, and (ii) a meaning latitudinal shift of seed zones, along with a contraction of species distributions for the period 1990–2030 in a northward direction. Some AFLP outliers were significantly associated with spring and winter precipitation, and with phosphorus concentration in the soil. According to the scenario for 2030, the estimated species and seed zone distributions will change both in size and position. Our modeling of seed zones could contribute to reducing the probabilities of maladaptation of future reforestations and plantations with the pine species studied.

Forest plantations and natural forests perform a relevant role in capturing CO₂ and reducing greenhouse gas concentrations. The objective of this study was to compare the diameter increment, biomass and carbon accumulation in a plantation of Pinus durangensis and a naturally regenerated stand. The data were collected from 32 circular plots of 100 m² (16 plots in the planted site and 16 in naturally regenerated area). At each plot, the diameter at the base (cm) and height (m) of all seedlings were measured using a Vernier and tape measure, and a seedling was destructively sampled collecting one cross-section at the base of the stump. The annual ring-width increment of each sampled seedling was recorded to obtain its diameter at the base and estimate annual aboveground biomass and carbon accumulation through allometric equations. The response variables were evaluated using mixed-effects ANOVA models. Results indicated that there were significant differences (P ≤ 0.05) on annual tree-ring width growth, biomass and carbon accumulation. The plantation seedlings showed significantly higher growth rates, biomass and carbon accumulation at most evaluated years. After 7 years of growth the lines of current annual increment (CAI) and mean annual increment (MAI) in basal diameter for both the plantation and the natural regeneration have not yet intersected. Both forest plantations and naturally regenerated stands of the studied tree species may be suitable alternatives to promote CO₂ capture and increase timber production.

La dosis de fertilizante en la producción de plantas en vivero depende del tipo de sustrato empleado, ya que ambos factores interactúan de manera positiva o negativa en los atributos morfológicos y fisiológicos de las plantas durante esta etapa de crecimiento. El objetivo del presente estudio fue determinar la eficiencia de tres sustratos y dos dosis de fertilizante de liberación controlada (FLC) en el crecimiento en vivero de Quercus durifolia. Los componentes de los sustratos (S) evaluados fueron turba de musgo, corteza compostada de pino y aserrín fresco de pino, en las siguientes proporciones: S1 (60-20-20), S2 (50-25-25) y S3 (33-33-33), con dos dosis de fertilizante (7 y 10 g L-1 de Multicote 8TM 18-6-12 de N, P y K). Se determinó que los tres sustratos evaluados mostraron resultados similares estadísticamente; sin embargo, las plantas fertilizadas con 10 g L-1 tuvieron mayor altura, diámetro, biomasa seca y más asignación de biomasa seca en hojas y tallo. Por lo tanto, incluir aserrín fresco de pino combinado con turba y corteza compostada de pino en partes iguales, con dosis de 10 g L-1 permite producir plantas de Q. durifolia con características morfológicas de calidad; además, el costo de producción disminuye. Esto es crucial para obtener plantas de calidad para proyectos de reforestación y restauración.

La tolerancia al frío tiene valor adaptativo en plantas perennes de clima templado-frío, por lo que es importante detectar variación genética en ella para árboles forestales. En dos ensayos de progenie de Pinus pseudostrobus establecidos en Pueblo Nuevo, Puebla (S1, 2853 m) y Teolocholco, Tlaxcala (S2, 2355 m), se determinó el índice de daño celular (ID) en plantas de cuatro años con una prueba de congelamiento, y se estimó su relación con el crecimiento en altura y variables bioclimáticas del sitio de origen de las familias en la región central de México. La tolerancia a frío se determinó con la pérdida de electrolitos (ID) a -15 °C durante 4 h. El análisis de varianza se realizó con Proc Mixed, usando un diseño de bloques completos al azar. El ID fue diferente (P<0.05) entre sitios y mayor en S1 (60.7%) que en S2 (50%); los parámetros genéticos indicaron que la tolerancia al frío está bajo control genético (h2f ≥0.50). El crecimiento en altura de las plantas en S2 fue mayor que en S1. Las variables bioclimáticas de mayor correlación (r≥0.55) con ID y el crecimiento en altura están relacionadas con la humedad, temperatura y precipitación de otoño-invierno. El daño por heladas en las familias varió entre sitios, lo que demuestra que existe interacción genotipo-ambiente asociada con resistencia al frío para algunas progenies; además de que los factores climáticos asociados con la humedad, la temperatura y precipitación también son importantes en la adaptación y crecimiento de las progenies de P. pseudostrobus