Pablo Martínez-Zurimendi

A Comparison of Isozyme and Morphological Markers to Assess the Within Population Variation in Small Populations of European aspen (Populus tremula L.) in Spain

Summary European aspen (Populus tremula L.) has been traditionally thought to establish new stands by vegetative propagation through root suckers produced by very few individuals (often only one). Morphological traits and isozyme patterns were studied in five small stands in northern Spain. Both isozyme and morphological approaches showed variation within and between stands. Estimated intrapopulational variation was higher than the expected, and clusters of individuals with the same isozyme multilocus patterns within each population have been identified. In order to check to what extent morphological markers are affected by the genotypes or clones, comparisons between leaf parameters and isozyme patterns were performed by hierarchical ANOVA and tests of hypothesis were constructed from the components of variance. Leaf shape parameters show a good correlation with the isozyme multilocus patterns. On the other hand, leaf size parameters, were more influenced by environmental factors. These traits may be useful as tools for the definition of in situ conservation units in endangered European aspen stands.

Influence of livestock systems with live fences of Gliricidia sepium on several soil properties in Tabasco, Mexico

The aim of the current study was to evaluate the effects of two livestock systems, a livestock system with live fences (LSLF) of Gliricidia sepium associated with signal grass ( Brachiaria decumbens ) and a livestock system based on a grass monoculture (LSPM), on specific physical and chemical soil characteristics at different depths and distances from the fence. In each system, we randomly selected 9 plots of 600 m 2 . A completely randomized design was used with a 2 x 3 factorial arrangement in which we analyzed the influence of the livestock systems (LSLF and LSPM), soil strata (0-10, 10-20 and 20-30 cm) and the interaction of both factors using a multivariate analysis of variance. In addition, we performed analysis of variance to determine the effect of distance sampling in the LSLF (0-3, 3-6 and 6-9 m). The LSLFs were associated with higher (P 0.05) at different depths and distances from the live fences. However, the soil pH varied between soil depths in the LSPM. Regarding the physical soil properties, only the sand and clay content varied (P 0.05). Sin embargo, pH del suelo vario entre las profundidades del suelo en los SGMP. En cuanto a las propiedades fisicas del suelo, solo las proporciones de arena y arcilla variaron a diferentes profundidades en ambos sistemas, pero no a diferentes distancias de los sistemas ganaderos con cercas vivas (P≤0.05). Se concluye que los SGCV tienen un enorme potencial para mejorar sustancialmente las propiedades fisicas y quimicas del suelo, siendo una oportunidad para frenar el deterioro de los suelos en sistemas de produccion ganaderos basados en el monocultivo de pasto.