Investigaciones Geograficas最新文献

Geomorphological inquiry has addressed the relation of cultural landscape features, such as land use, with landforms in different environments and under different land use regimes. Usually, these complex relationships have been pursuit by simple map overlaying in a geographic information system (gis). This research argues that the results of map overlaying need to be followed by statistical analyses to properly depict the nature of such relationships. The paper explores the quantitative relation between landforms and land use in a highly geographically complex region in the tropical dry Mexican Pacific coast. Data collection encompassed two phases: preliminary satellite image interpretation, and field verification and ground survey. Digitized and orthorectified layers were incorporated and overlain in a gis. Correspondence Analysis (ca) was used to identify correlations among land uses and landforms. Results showed a significant correspondence between geomorphic and land use entities. Fluvial landforms were associated to simpler patterns of human activity. Denudational landforms, on the other hand, depicted more complex and diverse land use patterns. Agricultural and grazing activities occurred in both gentle, fluvial landforms, and steep denudational landforms. Results were discussed in the light of their relevance for land use planning. This approach may strengthen decision making procedures particularly in such areas where applied geographic data need to be created to perform sound land use planning at the local scale.

Chile is one of the oecd countries with higher levels of socioeconomic segregation in its educational system. This may be explained by the incidence of institutional factors (fees and school selection processes), sociocultural factors (families’ appraisals and behaviors towards school choice) and contextual factors, among which residential segregation would stand as the most relevant.

This article analyzes the relation between school location, students’ socioeconomic status and student's place of origin (mobility). The data used was gathered from 1613 surveys responded by primary students’ families. The results evidence that residential segregation only partially influences educational socioeconomic segregation, since the capacity of mobility is a key factor to “break” the association between both phenomena. Therefore, residential segregation would affect to a greater extent low socioeconomic status students who attend schools near their homes and travel distances shorter than children from higher socioeconomic status, who tend to cover longer distances between home and school. Nevertheless, the comparative analysis of the cases complicates drawing conclusions, because students of equal socioeconomic status travel very different distances. The characteristics of the territories where schools are located shed some light on the cause of these differences. From these results, we propose re-discussing the use of the residential segregation concept for explaining phenomena like school segregation, due to the complex interrelations between both territorial fragmentation and urban mobility.

Forest pests are pathogens that cause mechanical or physiological damage to trees, such as deformations, disrupted growth, weakening, or even death, leading to important ecological, economic and social impacts. This study focused on the development of a technique for the detection of forest pests using infrared aerial photography. The general reflectance characteristics of healthy and damaged leaves are currently well known; Reid (1987) already described these features, with a shift toward blue and a reduced infrared reflectance as the dominant effects. As the plant disease progresses, the above effects become more apparent. The use of infrared digital aerial photographs allowed to obtain VIR (visible + infrared) images with four bands and a resolution of approximately one meter per pixel. Trees with some degree of deterioration and even dead individuals were identified and located through visual interpretation.

Color and infrared digital aerial photographs captured in March 2009 were used; two cameras were used: a Nikon D2X camera for the acquisition of images in the visible range (EV), and a Canon EOS Digital Rebel camera for infrared (IR) images. Once individual photographs were processed and organized, V and IR images were superimposed using the Photoshop editing program (Adobe™) Once composite V+IR (VIR) images were obtained, those covering the sampling area were selected and georeferenced. Rectified images were required to elaborate a mosaic encompassing the sampling area. The rectified images and the final mosaic had a spatial resolution of 90 centimeters per pixel.

The detection technique was designed using three methodological approaches: automatic, semi-automatic and manual processes. The semi-automatic and automatic modalities correspond to an assisted and unassisted spectral classification, respectively, while the manual method consisted in the direct observation of the photographs processed. The technique developed used as basis the photographic mosaic of the sampling area.

The unassisted and assisted spectral classification technique was carried out in the ERDAS Imagine image-processing software package. For the unassisted classification, tests were carried out considering various numbers of categories: 5, 10 and 15; the assisted classification included the spectral properties of each category used for the partition to group images into five categories: healthy forest, diseased forest, Juniperus scrubland, bare soil and shaded areas.

The accuracy of the technique for the detection of damaged trees was verified through field work, visiting different checkpoints where the health status of the tree was corroborated by direct observation and infrared photography at ground level.

A representative sampling area of the A. religiosa forest was established in the Monarch Butterfly Biosphere Reserve (RBMM), sufficient to encompass the largest number of damaged trees, but not