The propagation of Ramón (Brosimum alicastrum Sw.; Moraceae) in Mayan homegardens of the Yucatan peninsula of Mexico

In the Yucatan peninsula of Mexico, Maya natives have been propagating important species for centuries. However, little documentation exists of these methods, and traditional knowledge is fading as younger generations seek work in urban centers. With growing interest in using some of these species for plantation-scale production, this knowledge should be captured to aid in propagation and cultural methods of selected species. One such species, Ramón (Brosimum alicastrum Sw.), is grown in Mayan homegardens primarily as a source of dry season forage. We conducted a survey of Mayan families in several municipalities to determine basic propagation habits and procedures for cultivating Ramón, and used this information to conduct some controlled-environment studies of reproductive ecology of the species. Our survey showed that all or most Maya grow the Ramón tree in homegardens for forage and that the tree is both cultivated from wild seedlings as well as planted on a small scale. Propagation is by seed and young seedlings are irrigated until they are established. We examined the effects of temperature on seed germination and found that maximum germination occurred between 27° and 38 °C, with best germination and growth of healthy seedlings at 33 °C. No germination occurred below 21° or above 44 °C. Simulated Maya irrigation gave a four-fold increase in growth rate of seedlings, aiding early establishment. Watering gave seedlings of greater biomass, greater stem and root length, and greater numbers and size of leaves. This magnitude of response may provide an economic return for plantation culture of Ramón for forage production.     

Defining competition vectors in a temperate alley cropping system in the midwestern USA: 2. Competition for water

A study was carried out in an alley cropping system in the Eastern Maize Belt of the United States with the objective of quantifying the competition for water between trees (black walnut (Juglans nigra L.) and red oak (Quercus rubra L.) and maize (Zea mays L.). Spatial and temporal variation in soil moisture, tree and maize rooting patterns, tree and maize water uptake, and maize leaf area expansion were determined in three treatments; barrier (polyethylene root barriers separating maize and tree roots), trench (trenching without a polyethylene barrier), and no barrier (control). Significant temporal variation in soil moisture was observed in both black walnut and red oak alley cropping systems. The barrier and trench treatments resulted in higher soil moisture in the maize alley and lower soil moisture in the tree row than the no barrier treatment. Uptake of water by maize was higher in the barrier than the no barrier treatment. However, tree water uptake was higher in the no barrier treatment than in the barrier treatment because tree roots utilized water from the maize alley. Maize leaf area was negatively impacted by water stress in the no barrier treatment. Quantification of rooting patterns revealed that maize and tree roots were concentrated in the top 30 cm soil layer where water fluctuations were greatest. The barrier and trench treatments successfully eliminated the belowground root competition between trees and maize and resulted in greater leaf area and higher grain yields than the no barrier treatment. Thus, competition for water rather than competition for light seems to be critical in defining the productivity and sustainability of this alley cropping system.This revised version was published online in November 2005 with corrections to the Cover Date.     

Carbon, water and nutrient flux in Maya homegardens in the Yucatán peninsula of México

The Yucatán Peninsula of México has shallow soils and receives low amounts of precipitation, and has therefore low agricultural potential. Lacking large-scale irrigation from rivers and adequate rainfall, the indigenous Maya groups maintain agricultural productivity by adapting a variety of practices. Multistrata homegardens, one of their agricultural systems, have provided goods for trade, sale and personal consumption for many centuries. Nevertheless, an understanding of the controlling biological factors and interactions within these systems can lead to yield improvements. Photosynthetic rates, water use and litter production for a variety of species have been studied in these gardens to determine how Maya management impacts resource flow, productivity and diversity. When irrigated, diurnal photosynthetic rates nearly doubled for Manilkara zapota and water use increased two fold for M. zapota and Cordia dodecandra. Total litter production in traditional homegardens varied from 1,000 to 4,000 kg ha⁻¹ yr⁻¹ and ten arboreal species were found to contribute more than 33% of total litterfall biomass. Nutrient concentrations in the leaves of the predominant species were analyzed; Meliococcusbijugatus and Spondias purpurea were found to contribute the largest quantities of N, P and C. Our research indicates that species and structural diversity are critical to sustainability of homegardens, allowing efficient use and transfer of carbon, nutrients and water. This revised version was published online in June 2006 with corrections to the Cover Date.     

The structure of four home gardens in the Petén,Guatemala

Forest-covered home gardens around the tropical world vary in their structure, but serve to supply food and other products for direct family consumption or marketing. Little quantitative data exist defining home garden structure. Thus, this study was undertaken to examine the variation in home garden structures in response to market or household needs and the subsequent variation in light interception and productivity.Four home gardens were studied in the Department of the Petén, in northern Guatemala. Areal extent and height of canopies were mapped in transects through four gardens representing a range of site water regimes and market orientation. Light intensities incident on the ground were measured along each transect to assess light use. Results showed structural complexity, with full canopy closure in the one or more layers within the canopy for most gardens. The garden architectures made efficient use of light and space, with intersive management for food and fuel production. Farmers grew the crops for both cash and family subsistence. One home garden on a comparatively dry site with shallow soil seemed less structured, with only a single broken canopy layer, but with diverse species of plants.The results indicate that development of gardens in this area utilized existing trees, thinning them to leave the most useful, and inserting other desirable trees and shrubs in the understory and in open spaces. This strategy seemed to maximize light use, regardless of market orientation.This look at the structure and composition of four home gardens, in a forested area of current immigration, demonstrated (1) variety of organization and plant components, (2) different architecture for different soil/site conditions and market orientations, and (3) efficient use of available light through the arrangement of plants.     

The Call of the Wild: Call Centers and Economic Development in Rural Areas

This paper attempts to reflect critically on the role which telephone call centers might play in the economic development of rural places in the ‘information age’, drawing mainly on a case study of the Highlands and Islands of Scotland. It argues that although call center employment tends mainly to be urban‐based, the growth of this form of work does present opportunities for some rural areas. The paper considers the locational factors rural areas would have to possess or develop in order to attract such work. It suggests call centers can make a valuable, though limited, contribution towards rural economic development, principally through the creation of additional employment opportunities and the stimulation of new skills and competencies. It also suggests that call centers do not represent a panacea for rural areas and that, indeed, it would be dangerous for rural areas to become over‐reliant on employment in this sector.     

Virus-induced cholesterol crystals

One of the crystal types induced in cell cultures by a new feline herpesvirus was identified as cholesterol by crystal structure, polarized light microscopy, and mass spectroscopy.     

Clear air turbulence: detection by infrared observations of water vapor

"Forward-looking" infrared measurements of water vapor from the C-141A Kuiper Airborne Observatory of the National Aeronautics and Space Administration Ames Research Center show large, distinctly identifiable, signal anomalies from 4 to 10 minutes in advance of subsequent encounters with clear air turbulence (CAT). These anomalies are characteristically different from the signals not followed by CAT encounters. Results of airborne field trials in which the infrared radiometer was used indicate that, out of 51 situations, 80 percent were CAT alerts followed by CAT encounters, 12 percent were "false alarms" (CAT alerts not followed by CAT encounters), and 8 percent were CAT encounters not preceded by an infrared signal anomaly or CAT alert.     

Influence of ruminal insufflation on pulmonary function and diaphragmatic electromyography in cattle.

In 8 healthy, awake cows with permanent cannulated ruminal fistulas and carotid artery loops, respiratory mechanics, ventilation, and diaphragmatic electrical activity were studied before and during stepwise insufflation of the rumen with air pressure to 40 mm of Hg. We found that ruminal insufflation increased intraperitoneal, intrapleural, and transdiaphragmatic pressures and decreased lung volume and lung compliance. In individual cows with rumen insufflation there was an increase in pulmonary resistance, but this trend was not significant in the group. Peak expiratory flow rate was increased and peak inspiratory flow rate was unchanged. Inspiratory duration (Ti) decidal volume decreased slightly, breathing frequency decreased markedly, and minute volume decreased. When intraruminal pressure reached 40 mm of Hg, arterial partial pressure of carbon dioxide (PaCO2) increased (P less than 0.01) and that of oxygen (PaO2) decreased (P less than 0,01) and arterial blood pH decreased (P less than 0.02). Diaphragmatic electromyographic activity was increased, but mechanical effectiveness of the diaphragm was reduced at increased intraruminal pressures.