Edmundo García Moya

Soil Water Content Dynamics Along a Range Condition Gradient in a Shortgrass Steppe

Abstract Evidence is accumulating on the importance of plant cover and plant species composition on the control of ecosystem processes. In this study we examined a gradient considering the proportional contribution of the key species Bouteloua gracilis H.B.K. Lag. to assess its influence on the average and dynamic changes in soil water content in the shortgrass steppe from Central Mexico. We chose 4 sites with the following proportions of the key species: < 25%, 25%–50%, 50%–75%, and > 75%, ascribing each proportion to the range condition categories poor, fair, good, and excellent, respectively. Soil water measurements were carried out during 14 months at the 4 sites. Our results showed that range condition had a significant effect on soil water content (P < 0.01). The excellent condition was overall 14.5% and 12.5% lower soil moisture content compared to the poor and good range conditions (P < 0.01), respectively. Our results indicated a negative correlation between the gradient of soil water content with the range condition classes. Soil water content dynamics also differed among range condition classes, with the excellent condition showing both faster water recharge and extraction patterns than the other 3 range condition categories. Differences in soil water content among the range condition classes appeared to be related to morphological and physiological traits associated with the dominant species cover observed at each site. These results offer insights into the importance of vegetation characteristics as potential indicators of thresholds in grazing ecosystem processes such as soil water dynamics.

Afinidades en la flora genérica de piñonares del norte y centro de México: un análisis fenético

MEDIANTE UN ANALISIS DE CLASIFICACION FENETICA, SE DISCUTEN LAS AFINIDADES EN LA FLORA GENERICA DE LOS PINONARES MEXICANOS. EL ESTUDIO SE SUSTENTO EN EL REGISTRO DE 438 GENEROS DE PLANTAS VASCULARES DE 32 PINONARES MEXICANOS CARACTERIZADOS POR DISTINTAS ESPECIES COMO PINUS CEMBROIDES, P. JOHANNIS, P. MAXIMARTINEZII, P. MONOPHYLLA, P. QUADRIFOLIA, P. NELSONII, P. CULMINICOLA Y P. LAGUNAE. SE ELABORO UNA MATRIZ DE DATOS PRESENCIA/AUSENCIA DE LOS GENEROS EN LOS 32 PINONARES, CADA UNO DE LOS CUALES SE CONSIDERO COMO UNA UNIDAD GEOGRAFICA OPERATIVA. SE ESTIMARON 2 INDICES DE SEMEJANZA ENTRE LAS COMUNIDADES PINONERAS, Y DESPUES SE AGRUPARON MEDIANTE EL PROCEDIMIENTO UPGMA; LOS GRUPOS FORMADOS SE REPRESENTARON EN UN DENDROGRAMA. LOS PINONARES SE RELACIONARON, EN GENERAL, POR CERCANIA GEOGRAFICA Y POR SU LOCALIZACION EN UNA MISMA PROVINCIA FISIOGRAFICA. LOS PINONARES DE BAJA CALIFORNIA CARACTERIZADOS POR P. CUADRIFOLIA FORMARON UN GRUPO COMPACTO, LO MISMO QUE AQUELLOS DE P. CEMBROIDES DE CHIHUAHUA Y DE P. MAXIMARTINEZII DE ZACATECAS. EN EL GRUPO DE SAN LUIS POTOSI SE CONJUNTARON COMUNIDADES DE P. CEMBROIDES Y DE P. JOHANNIS; MIENTRAS QUE LAS PROPIAS DE P. NELSONII NO FORMARON UN GRUPO COHERENTE; LOS PINONARES DEL SUROESTE DE COAHUILA ESTAN MUY RELACIONADOS, PERO TIENEN DIFERENCIAS CON LOS DE MAS AL NORTE DE ESTE ESTADO. EL PINONAR DE P. CULMINICOLA DE NUEVO LEON ES EL MAS DIFERENTE DE LAS OTRAS COMUNIDADES DE PINONEROS.