Juan Martínez-Cruz

Ficus benjamina leaves as indicator of atmospheric pollution: a reconaissance study

We present a diagnostic study to evaluate the suitability of Ficus benjamina tree leaves as a captor of heavy metal particles from atmospheric dusts in urban areas. Leaf samples were taken at 16 localities within three areas in Morelia, state of Michoacán (Mexico’s medium size city, 830000 inhabitants). Measurements of magnetic susceptibility were conducted to determine the magnetic enhancement using samples from green, relatively unpolluted area, as a reference. The samples collected at areas with heavy traffic (main avenues) yielded values almost ten times higher than the values obtained for the unpolluted reference. Isothermal Remanent Magnetization curves are proportional to the degree of pollution. Associations of almost pure magnetite with heavy metals were revealed by scanning electron microscope.

Management practices and diversity of flower visitors and herbaceous plants in conventional and organic avocado orchards in Michoacán, Mexico

ABSTRACT Despite alleged advantages of organic over conventional farming, management effects on biodiversity are still little known. We related the diversity of herbs and flower visitors to management indicators in avocado orchards and hypothesized that inputs, practices, and context influence diversity of herbs and flower visitors. Using basic classification units, matrix correlation, and multivariate analysis of variance, we found that low-toxicity insecticides, infrequent herb cutting, and presence of forest areas were related to high biodiversity. Intensification of agricultural management reduced biodiversity both in organic and conventional management type. Our results advocate for an improved, integrative, management classification considering intensification and ecological context, besides input-type criteria.