Cultivation of C 3 and C 4 crops in semi-arid regions will be severely constrained as global temperatures rise. Consequently, alternative crops need to be sought out that adapt well to heat and drought and are productive despite limited access to water. Traits, such as crassulacean acid metabolism (CAM), enable economically important species such as those in the Agave genus adapt to drought and high temperatures. The succulence and high efficiency of agaves, which enables them to produce biomass with little water, underscores their feasibility as an alternative crop for semi-arid regions, such as the Sonoran Desert in the southwestern U.S. In this paper, we offer a review of the suitability for cultivation of agaves via dryland farming, particularly by rock mulching techniques used by pre-Columbian, Sonoran Desert farmers. This analysis dovetails with information also provided on the biological traits of Agave and its historical and present utilization. Pre-Columbian, Hohokam dryland farmers used rock mulching in the form of rock piles to cultivate agaves. Rock piles acted as a type of mulch to harvest rainfall and to retain soil moisture, which allowed the Hohokam to intensively cultivate agaves during multi-year droughts. Remains of Hohokam rock mulching for agave production can be found at archaeological sites in central Arizona, which provides evidence of the utility of dryland farming and ancient agricultural innovation to reconcile water scarcity in the region. Moreover, the use of rock piles likely bolstered Agave productivity in marginal lands. Although little is known of historic rock mulching to cultivate agaves and its biological implications on plant productivity we suggest its application as a dryland farming model could be a sustainable strategy in the U.S. Southwest.

Pinus greggii is a species of socioeconomic importance in terms of wood production and environmental services in Mexico, though it is restricted by particular environmental conditions to the Sierra Madre Occidental. Species distribution models are geospatial tools widely used in the identification and delineation of species' distribution areas and zones susceptible to climate change. The objectives of this study were to: (i) model and quantify the environmentally suitable area for Pinus greggii in Mexico, and possible future distributions under four different scenarios of climate change; (ii) identify the most relevant environmental variables that will possibly drive changes in future distribution; and (iii) to propose adequate zones for the species' conservation in Mexico. Some 438 records of Pinus greggii from several national and international databases were obtained, and duplicates were discarded to avoid overestimations in the models. Climatic, edaphic, and topographic variables were used and 100 distribution models for current and future scenarios were generated using the Maxent software. The best model had an area under the curve (AUC) of 0.88 and 0.93 for model training and validation, respectively, a partial ROC of 1.94, and a significant Z test (p<0.01). The current estimated suitable area of Pinus greggii in Mexico was 617,706.04 ha. The most relevant environmental variables for current distribution were annual mean temperature, mean temperature of coldest quarter, and slope. For the 2041-2060 models, annual mean temperature, precipitation of coldest quarter, and slope were the most important drivers. The use of climatic models allowed to predict a future decrease in suitable habitat for the species by 2041-2060, ranging from 48,403.85 (7.8%-HadGEM2-ES RCP 8.5 model) to 134,680.17 ha (21.8%-CNRM-CM5 RCP 4.5). Spatial modeling of current and future ecological niche of Pinus greggii also allowed to delineate two zones for in situ conservation and restoration purpose in northeastern (Nuevo Leon) and central (Hidalgo) Mexico.

México es el único productor y exportador a nivel mundial de la cera de candelilla, pero el mercado internacional se establecieron restricciones con la finalidad de disminuir la presión sobre el recurso natural por la sobreexplotación, por lo que actualmente se encuentra incluida en la lista de la Convención Internacional sobre el Comercio de Especies Amenazadas de Fauna y Flora (CITES). El objetivo fue identificar las propiedades del suelo que favorecen la distribución de la candelilla, mediante el método de máxima entropía, buscando promover su manejo y aprovechamiento sustentable. El área de estudio fueron dos localidades de los municipios de Cuatro Ciénegas y Viesca, Coahuila. Se obtuvieron 102 y 72 sitios de muestreo en los que se registraron las coordenadas, los datos biométricos de los ejemplares, las condiciones del hábitat, del relieve y del tipo de suelo. Se seleccionaron nueve propiedades edáficas, para lo que se descargaron los archivos de la base de datos Soilgrid, la modelación se realizó en el programa Maxent. Como resultados el área bajo la curva en cada localidad con valores 0.927 y 0.973, se considera como un modelo adecuado para determinar la distribución actual de la especie. En el suelo, los factores físicos que fueron determinantes para favorecer la presencia de candelilla fueron: densidad aparente, profundidad y pedregosidad, mientras que los factores químicos: capacidad de intercambio catiónico y el contenido de carbono orgánico.

El conocimiento de la distribución de las especies en relación con las condiciones bióticas y abióticas permite conocer las posibles respuestas de las especies a los cambios, ubicar la presencia geográfica de especies de importancia comercial. Los objetivos fueron Identificar las variables bioclimáticas que determinan la distribución de poblaciones de E. antisyphilitica y estimar la distribución potencial de la especie en las zonas áridas usando dos métodos Maxent y Bioclim. Los datos de presencia fueron del inventario nacional de E. antisyphilitica y se usaron 19 capas climáticas de Worldclim con una resolución espacial de l km2 . Se procesaron con el método de máxima entropía además los requerimientos de temperatura y precipitación se analizaron con la comparación de variables bioclimáticas, la predicción de la modelación de la distribución y la salida geográfica u Las variables de precipitación influyen más que las de temperatura sobre la distribución de E. antisyphilitica, en un intervalo de precipitación de 200 a 500 mm. La modelación y salida geográfica usando BIoclim de Diva-Gis 7.5® y Maxent® -3.4.1. Las variables de precipitación contribuyeron con el 67.7 % y las variables de temperatura aportaron 32.4%, por lo tanto, en la distribución de E. antisyphilitica, donde la precipitación es el principal factor que inflluye en la presencia de la especie seguida de las variables de temperatura. Maxent es mejor modelo que Bioclim de Diva-Gis para determinar la superficie potencial que ocupa E. antisyphilitica y permite obtener imágenes de calidad con resolución mayor, esto representa una ventaja para estimar las áreas de distribución de poblaciones de candelilla.

El mezquite es uno de los recursos forestales más importantes del norte de México, constituye una parte importante de la flora nacional y es de gran importancia para los habitantes de las zonas áridas y semiáridas. El presente trabajo generó una tabla de volumen en m3 y peso de madera a nivel de predio que puede utilizarse en el área de influencia. Se utilizó el análisis dimensional, con medidas de fácil obtención en los árboles, que permite a los productores, técnicos forestales e instituciones contar con parámetros de producción y volumen de madera para el aprovechamiento racional y sustentable de las poblaciones naturales de mezquite. La evaluación se realizó en los terrenos del Ejido San Antonio de la Sierrecilla, municipio de Mazapil, Zacatecas, México; se realizó un muestreo destructivo de 39 árboles, se midió el diámetro de copa y altura total en cm, las ramas se cubicaron y se pesaron. En el análisis de regresión se utilizó el modelo polinomial, resultando el volumen (m3) = 2,341E-6X2-0,0012X+0,1803 y la determinación de peso fresco (kg)=0,001X2-0,556X+81,909*D con 95% de confiabilidad.

One of the conifers that survived after the last glaciation is the Pseudotsuga menziesii (Mirb.) Franco. Due to the gradual increase in temperature, this species was forced to move from the south to the north and to higher elevation, causing a fragmented and intermittent distribution in Mexico. The main objective of this study was to model and identify suitable areas for the future conservation of the P. menziesii in Mexico. The specific objectives of this research were: (i) to model the habitat suitability of P. menziesii in Mexico, (ii) to identify the most relevant environmental variables based on its current and future habitat suitability (2030, 2050, 2070 and 2090) and (iii) to suggest areas for the conservation of the species in Mexico. Records were compiled from different national and international sources. Climate and topographic variables were used. With MaxEnt software version 3.4.3 (Phillips, New York, NY, USA) 100 distribution models were obtained, where the model showed an area under the curve of 0.905 for training and 0.906 for validation and partial ROC of 1.95 and Z reliable (p < 0.01), with TSS values > 0.80. The current area of the P. menziesii was 31,580.65 km2. The most important variables in the current and future distribution were maximum temperature of the hottest month, precipitation of the coldest trimester and average temperature of the coldest trimester. The percentage of permanence (resilience) for the 2030, 2050, 2070 and 2090 climate horizons was 49.79%, 25.14%, 17.45% and 16.46%, respectively, for the SSP 245 scenario. On the other hand, for the SSP 585 scenario and the analyzed horizons, the percentage resilience in areas of suitable habitat zones was 41.45%, 27.42%, 9.82% and 2.89%.

<p><strong>Background.</strong> Mezquite gum (<em>Prosopis laevigata</em> [Humb. &amp; Bonpl. ex Willd.]) is similar to the gum Arabic; its production is associated to the stress condition of the tree. <strong>Objective.</strong> To induce and evaluate the gum production and quality. <strong>Methodology.</strong> A completely randomized design with factorial arrangement was used, factor one was seasons (spring and autumn), factor two was tree heights (2.0 and 3.0 m) and factor three was the application of two products, acid 2 -chloroethyl- phosphone (Etherel 240^®) + distilled water and a control (distilled water). <strong>Results.</strong>  The gum was produced only in primary branches between 10 and 15 days after applying 2-chloroethyl phosphonic acid + distilled water. Gum production was higher in autumn in 3.0 m trees, with an average of 57 g per tree. A yield of 10.8 kg ha^-1 of gum with a density of 190 trees ha^-1 was estimated. The content of ash and protein in gum was higher in trees of 2.0 m in autumn, while the content of fiber and nitrogen-free extract in gum was higher in trees of 3.0 m in autumn. The moisture and fat content in gum was higher in spring in trees of 2.0 and 3.0 m, respectively. The pH of the gum was less acid in 3.0 m trees in spring with a lower content of impurities. <strong>Implications.</strong> It is suggested to carry out other tests to determine the presence of acid 2-chloroethyl-phosphonic in the chemical composition of the gum. <strong>Conclusion.</strong> The application of acid 2-chloroethyl-phosphonic (20%) + distilled water stimulated gum secretion in mesquite trees. Trees treated with distilled water (control) did not produce gum.</p>

Background Studies in Mexico have shown that the genus Pine has always been under evolutionary changes, however currently they have accelerated as a result of human activities. Pinus greggii is a species restricted by particular environmental conditions of the Sierra Madre Occidental, which is of socio-economic importance in terms of wood production and provides environmental services to the ecosystem. Species distribution models are a relevant geospatial tool in decision making, and notable applications exist such as identifying areas of distribution and zones susceptible to climate change. The objectives of this study were: 1) model and quantify the current distribution, and possible future distribution under four scenarios of climate change; 2) identify the most relevant environmental variables that drive changes in distribution; and 3) to propose adequate zones for the species’ conservation in Mexico. Methods 438 records of Pinus greggii from several national and international databases were obtained, and were cleaned up to get rid of duplicates and overestimations in the models. Climatic, edaphic, and topographic variables were used and were generated 100 distribution models for current and future scenarios with Maxent software. Results The model one under replicated of crossvalidation had the best statistic, with an area under the curve of 0.88 and 0.93 for model training and validation, respectively, a partial ROC of 1.94, and a significant Z test (p < 0.01). The current estimated area of Pinus greggii in Mexico was 617,706.04 ha and the most important environmental variables for current distribution were the annual mean temperature, mean temperature of coldest quarter, and slope. For the 2041–2060 models, annual mean temperature, precipitation of coldest quarter, and slope were most important. The future models (2041–2060) predict a decrease in suitable habitat for the species from 48,403.85 (7.8%; HadGEM2-ES RCP 8.5 model) to 134,680.17 ha (21.8%; CNRM-CM5 RCP 4.5). Conclusions The spatial modeling of current and future conditions of the ecological niche of Pinus greggii in this study allows the proposal of two zones for conservation purpose and in situ restoration for the species in northeastern (Nuevo Leon) and central (Hidalgo) Mexico.