Spatial pattern and ecological process in the coffee agroforestry system

The coffee agroforestry system provides an ideal platform for the study of spatial ecology. The uniform pattern of the coffee plants and shade trees allows for the study of pattern generation through intrinsic biological forces rather than extrinsic habitat patchiness. Detailed studies, focusing on a key mutualism between an ant (Azteca instabilis) and a scale insect (Coccus viridis), conducted in a 45-ha plot in a coffee agroforestry system have provided insights into (1) the quantitative evaluation of spatial pattern of the scale insect Coccus viridis on coffee bushes, (2) the mechanisms for the generation of patterns through the combination of local satellite ant nest formation and regional control from natural enemies, and (3) the consequences of the spatial pattern for the stability of predator-prey (host-parasitoid) systems, for a key coccinelid beetle preying on the scale insects and a phorid fly parasitoid parasitizing the ant.     

Quality of Agroecological Matrix in a Tropical Montane Landscape: Ants in Coffee Plantations in Southern Mexico

Abstract: Conservation efforts in fragmented landscapes frequently focus on characteristics of the habitat fragments. We propose that the matrix within which habitat fragments occur is of equal importance and focus on quality of the matrix as an interesting variable. We studied ground-foraging ants in isolated montane forest fragments in the matrix of coffee agroecosystems of southwestern Chiapas, Mexico. We sampled the ants, with tuna fish as bait, in plots at various distances from a forest fragment (2–750 m) on two farms, one an organic farm with considerable shade, the other a conventional farm with only spotty shade. Each plot contained a grid of 49 ( 7 × 7) or 100 (10 × 10) baits. The species richness of ground-foraging ants was not significantly different between the forest fragment and the high-quality matrix, but it was significantly lower in the low-quality matrix than in the forest. Furthermore, species richness decreased with distance from the forest fragment in both matrix types. However, the rate of decrease in species richness was greater in the conventional farm ( poor-quality matrix) than in the organic farm ( high-quality matrix), suggesting that the quality of the agricultural matrix is important for the conservation of ant diversity.     

Cadmium sorption by sodium and thiourea-modified zeolite-rich tuffs

In the present investigation, two zeolite-rich tuffs from Guaymas and El Cajon(State of Sonora), which were conditioned with a sodium chloride solution and subsequently modified with a thiourea solution, were chosen to evaluate the removal of Cd from aqueous systems. The zeolitic materials were characterized by scanning electron microscopy and X-ray diffraction. The surface area was also determined. The experiments were performed in a batch system, and the influences of p H, contact time between phases, and the concentration of Cd in the solution on the adsorption by sodium or thiourea-modified zeolite-rich tuff were investigated. It was found that the efficiency of Cd ion removal from aqueous solutions is influenced by the p H of the aqueous systems. The Cd adsorption kinetic data were well fitted to a pseudo-second-order model in all cases. The Langmuir and Langmuir–Freundlich isotherms adequately described the Cd sorption behavior by the zeolite from El Cajon pretreated with Na Cl and the zeolite from Guaymas modified with thiourea, respectively.