Agave lechuguilla Torr., of the family Agavaceae, is distributed from southwestern United States to southern Mexico and is one of the most representative species of arid and semiarid regions. Its fiber is extracted for multiple purposes. The objective of this study was to generate a robust model to predict dry fiber yield (Dfw) rapidly, simply, and inexpensively. We used a power model in its linear form and bioclimatic areas as dummy variables. Training, generation (80%) and validation (20%) of the model was performed using machine learning with the package ‘caret’ of R. Using canonical correlation analysis (CCA), we evaluated the relationship of Dwf to bioclimatic variables. The principal components analysis (PCA) generated two bioclimatic zones, each with different A. lechuguilla productivities. We evaluated 499 individuals in four states of Mexico. The crown diameter (Cd) of this species adequately predicts its fiber dry weight (R² = 0.6327; p < 0.05). The intercept (β₀), slope [lnCd (β₁)], zone [(β₂)] and interaction [lnCd:Zona (β₃)] of the dummy model was statistically significant (p < 0.05), giving origin to an equation for each bioclimatic zone. The CCA indicates a positive correlation between minimum temperature of the coldest month (Bio 6) and Dwf (r = 0.84 and p < 0.05). In conclusion, because of the decrease in Bio 6 of more than 0.5°C by 2050, the species could be vulnerable to climate change, and A. lechuguilla fiber production could be affected gradually in the coming years.

Caracterización morfológica y genética de las ectomicorrizas formadas entre Pinus montezumae y los hongos presentes en los bancos de esporas en la Faja Volcánica Transmexicana

Sphagnum peat moss is one of the most commonly used substrates for forest plant and houseplant production. It is extracted from peat bogs in the circumboreal region and exported worldwide. Commercial peat moss is pasteurized, and is therefore believed to be free of viable ectomycorrhizal propagules. We used a bioassay with Pinus montezumae to demonstrate that commercial peat moss carries viable ectomycorrhizal spores, able to form mycorrhizae. Ectomycorrhizal fungi on seedling root-tips were sequenced for phylogenetic analyses using the ITS rDNA barcode region. We found three species: Suillus brevipes, Sphaerosporella brunnea, and Thelephora terrestris. S. brevipes and T. terrestris were found as viable inoculum transported in the peat moss, while S. brunnea was a greenhouse contaminant. S. brevipes and T. terrestris have biological characteristics (such as heat resistant and long living spores) that facilitate their survival to the extraction, transport, and storage processes of peat moss. This allows them to colonize nursery seedlings and to become potential invasive species in plantation areas. S. brevipes and T. terrestris are two of the most introduced fungi by anthropic activities; it has been argued that the vehicle for the introductions are their pine symbionts. This is the first time it has been demonstrated that peat moss is an important vehicle for the introduction of these fungi; a fact potentially related to the pattern of introduction of these ectomycorrhizal species from the northern hemisphere to elsewhere in the world.

La importancia del valor económico del género Pinus spp. como un recurso natural en México se basa en su presencia en 75 % de su superficie. El estudio que se documenta se orientó a cuantificar el valor monetario que aporta a la economía forestal; para ello se consideraron los datos estadísticos de la Secretaría del Medio Ambiente y Recursos Naturales (Semarnat), de los cuales se examinó un horizonte de 15 años (2002-2016), con la idea de conocer el comportamiento y evolución del valor de esta conífera; y en el que se segmentó el correspondiente al pino como madera en rollo y en escuadría. El proceso metodológico consistió en actualizar los valores corrientes por medio de la deflactación y mostrarlos a valores constantes, para lo cual se seleccionó como año base el 2013. De esa manera, los datos fueron comparables para conocer sus tendencias; también, se cuantificó su variación por medio de la función estadística tasa media de crecimiento anual. En términos reales, la importancia del valor del pino disminuye, sobre la cual tienen una fuerte influencia los precios de mercado que no crecen lo suficiente para detener la caída del valor de la producción; situación que se acentúa en el rubro de la madera en rollo, con respecto al de la escuadría.

Mexico is home to the highest species diversity of pines: 46 species out of 113 reported around the world. Within the great diversity of pines in Mexico, Pinus culminicola Andresen et Beaman, P. jaliscana Perez de la Rosa, P. maximartinenzii Rzed., P. nelsonii Shaw, P. pinceana Gordon, and P. rzedowskii Madrigal et M. Caball. are six catalogued as threatened or endangered due to their restricted distribution and low population density. Therefore, they are of special interest for forest conservation purposes. In this paper, we aim to provide up-to-date information on the spatial distribution of these six pine species according to different historical registers coming from different herbaria distributed around the country by using spatial modeling. Therefore, we recovered historical observations of the natural distribution of each species and modelled suitable areas of distribution according to environmental requirements. Finally, we evaluated the distributions by contrasting changes of vegetation in the period 1991–2016. The results highlight areas of distribution for each pine species in the northeast, west, and central parts of Mexico. The results of this study are intended to be the basis of in situ and ex situ conservation strategies for the endangered Mexican pines.

Management of forest genetic resources requires experimental data related to the genetic variation of the species and populations under different climatic conditions. Foresters also demand to know how the main selective drivers will influence the adaptability of the genetic resources. To assess the inter- and intraspecific variation and plasticity in seedling drought tolerance at a relevant genetic resource management scale, we tested the changes in growth and biomass allocation of seedlings of Pinus oocarpa, P. patula and P. pseudostrobus under two contrasting watering regimes. We found general significant intraspecific variation and intraspecific differences in plasticity, since both population and watering by population interaction were significant for all three species. All the species and populations share a common general avoidance mechanism (allometric adjustment of shoot/root biomass). However, the intraspecific variation and differences in phenotypic plasticity among populations modify the adaptation strategies of the species to drought. Some of the differences are related to the climatic conditions of the location of origin. We confirmed that even at reduced geographical scales, Mexican pines present differences in the response to water stress. The differences among species and populations are relevant in afforestation programs as well as in genetic conservation activities.