Candelilla (Euphorbia antisyphilitica Zucc.) is a shrub species distributed throughout the Chihuahuan Desert in northern Mexico and southern of the United States of America. Candelilla has an economic importance due to natural wax it produces. The economic importance and the intense harvest of the wax from candelilla seems to gradually reduce the natural populations of this species. The essence of this research was to project the potential distribution of candelilla populations under different climate change scenarios in its natural distribution area in North America. We created a spatial database with points of candelilla presence, according to the Global Biodiversity Information Facility (GBIF). A spatial analysis to predict the potential distribution of the species using Maxent software was performed. Thirteen of 19 variables from the WorldClim database were used for two scenarios of representative concentration pathways (RCPs) (4.5 as a conservative and 8.5 as extreme). We used climate projections from three global climate models (GCMs) (Max Planck institute, the Geophysical Fluid Dynamics Laboratory and the Met Office Hadley), each simulating the two scenarios. The final predicted distribution areas were classified in five on-site possible candelilla habitat suitability categories: none (< 19%), low (20–38%), medium (39–57%), high (58–76%) and very high (> 77%). According to the area under the curve (0.970), the models and scenarios used showed an adequate fit to project the current and future distribution of candelilla. The variable that contributed the most in the three GCMs and the two RCPs was the mean temperature of the coldest quarter with an influence of 45.7% (Jackknife test). The candelilla’s distribution area for North America was predicted as approximately 19.1 million hectares under the current conditions for the high habitat suitability; however, the projection for the next fifty years is not promising because the GCMs projected a reduction of more than 6.9 million hectares using either the conservative or extreme scenarios. The results are useful for conservation of the species in the area with vulnerable wild populations, as well as for the selection of new sites suitable for the species growth and cultivation while facing climate change.

Debido a la falta de métodos para estimar con precisión la pérdida de suelo en México, es necesario realizar estudios experimentales para estimar la erosión basada en datos validados. Por lo que el objetivo de esta investigación fue estimar la Tasa de Erosión Anual (A) para diversas coberturas de suelo empleando la Ecuación Universal de Pérdida de Suelo (EUPS), y ajustada mediante su relación con el índice de Generación de Sedimentos (IGS) obtenido en lotes de escurrimiento. Los resultados muestran que, durante el período y las condiciones de este estudio: EUPS subestima el valor de A al calcular la erosividad de la lluvia con el Índice Modif icado de Fournier (RIMF) en los tratamientos con Vegetación Natural (VN) y Roturación con Esquilmo (RE). Los suelos sin coberturas ref lejaron mayor IGS. Las ecuaciones obtenidas con la relación IGS vs A, de los tratamientos con Suelo Desnudo (SD) y Roturados (RT), pueden ser empleadas para ajustar la tasa de pérdida edáf ica en suelos con características similares a las del estudio, cumpliéndose de forma parcial el objetivo de este trabajo.

Erosion estimates for black soils in Mexico based on the Universal Soil Loss Equation (USLE) present discrepancies due to generalizations that lead to errors in permissible limits, with the erodibility factor or K factor (FK) being the most sensitive. The objective of the present investigation was to obtain a reasonable FK range for a Phaeozem (PH) from central Mexico by contrasting two equations based on the USLE. Samples were randomly obtained at three sites (P1, P2, P3) of a four-hectare area. The percentage of organic matter, textural class, soil structure, and profile permeability were determined. The results reveal differences between the estimated FK (FKe) and reference FK (FKr), whose values were +0.015, +0.028, and +0.029 for P1, P2, and P3, respectively. The differences represent underestimations that are up to 1.7 times greater in magnitude for FKr with respect to FKe. The statistical analysis rejects the null hypothesis (H0) that the means of each site evaluated are the same (P1 = P2 = P3). Although the variances between the factors of erodibility obtained using the equation specific to the Mollisols in Yunnan Province, China, and the reference nomography developed primarily in United States are significantly different (α ≥ 0.01), a combination of both could provide a range of maximums and minimums in the FK estimates and would yield better results than with the use of default values that tend to underestimate erosion rates.

Los objetivos de la investigación fueron: 1) Evaluar los impactos probables del cambio climático (CC) en la agricultura de secano (AS) en Aguascalientes, México, con base en el modelo HadGEM2-ES para el forzamiento radiativo 8.5 en un futuro cercano, 2015-2039; y 2) Determinar la magnitud de los impactos del CC en la aptitud productiva de la AS a través del análisis de la variabilidad de la precipitación media anual (PMA). La unidad de estudio comprendió el territorio de Aguascalientes, cuyos climas predominantes son semiseco [BS1k w, BS1hw(w)] y templado subhúmedo [C(wO)], y PMA de 526 mm. La evaluación del impacto potencial del CC en la AS de Aguascalientes se basa en el análisis de características edáficas y topográficas en las cuales se practica esta actividad y se complementa con el análisis de la PMA para el futuro cercano, apoyados con imágenes satelitales tipo SPOT. Los resultados indican incrementos probables en la PMA del 20 %, lo cual no necesariamente garantiza un impacto positivo en la productividad del cultivo de maíz, ya que hay factores asociados a las condiciones edáficas, topográficas y de las políticas de uso de la tierra que determinan el éxito del mismo.