Sistema Regional de Información
en línea para Revistas Científicas de América Latina,
el Caribe, España y Portugal

This paper explores and discusses the methodological problems facing regional history.  An approach, rather than a discipline, seemingly clear and defined, is focused in the  discussion since historians have trusted more on geographical and natural contents, seen as part of regional studies, as overarching frameworks of their analysis than in social processes and their methods. Concepts such as “microhistory”,  “regional  history”, and “subnational” history  are delineated in order to try and define  the main historiographical stances current today regarding this field. This is done  to locate better a specific kind of explanation of the past, whose main concern has been the reconstruction of part or all of the aspects of the life of a region.

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Environmental problems can emerge in any kind of territory, landscape, geosystem or ecosystem. However, in geomorphic terms mountains are amongst the most fragüe, impacted and modified units, as a result of their physico-geographical characteristics -mostly geomorphic- and of the diversity of their natural resources. Human impacts take place on a physical-geographical framework in which landforms play both an active and a passive role. This research aims to present the main geomorphic criteria for environmental analysis, in the form of elements and attributes, taking a Cuban mountainous area with a moderate landform energy as an example. A procedure to determine the extent of landform stability by defining a unit, namely the morphotectonic block, is hereby proposed. This would allow to perform a comprehensive assessment of the geomorphic factor by using endogenous variables (blocks and faults with recent rapid or slow vertical tectonic activity; maximum uplifting of each block; maximum displacement between contiguous blocks; upper category for the morpho-tectonic limit; and length and density of morpho-alignments) and exogenous variables (slope angle and aspect, vertical and horizontal stream erosion, relief, morpho-lithologic complexes). Factor analysis, cluster analysis and histograms are used to determine the relative weight of each variable and to quantify the geomorphic dynamics. The scope of this work cannot be considered solely as an environmental geomorphology subject, but is rather an attempt to apply geomorphic knowledge to environmental analysis. The final result are maps showing types of blocks classified according to their endogenous, exogenous and general dynamics.

L´interprétation de photographies aériennes et l´élaboration d´un système d´information géographique ont permis la reconnaissance géomorphologique et hydrographique de la Réserve de la Biosphère de Calakmul. On a procédé à la digitalisation des cartes topographiques au 1:50 000 en courbes de niveau d´équidistance 10 mètres ainsi qu´à l´interprétation des traits physiques et hydrographiques à partir de photographies aériennes au 1:25 000 corrigées digitalement afin d´être incorporées au système d´information géographique. Les géoformes de la zone d´étude ont été classées en fonction de leur morphologie et sur la base des traces de processus d´érosion et de dissolution karstique. Les unités de relief sont classées en types de versants, surfaces structurales d´origine karstique, vallées fluviales et karstiques, plaines structurales et zones inondables, périodiques et permanentes. Le réseau hydrographique superficiel est peu développé car prévalent des conditions d´inflitration des eaux pluviales et fluviales qui favorisent l´alimentation des nappes aquifères.

The long lasting study of climate through the systematic analysis of documentary sources is among the so called proxy-records, registrations used in order to recognize the climatic behaviour during several centuries. This methodological possibility has been hardly practiced in Mexico until the late Twentieth Century, thus, the background in this kind of research was not meant to distinguish the climatic behaviour in a regional scale during large periods of droughts time, in fact, it aimed to relate certain socioeconomic events with climatic anomalies. At the same time, it was a research not based in continuos and homogeneous documentary sources, condition accomplished by the rogation ceremonies records registered in the books of the civil and ecclesiastic files; these archives were carefully inspected since the beginning of their recording until the decade of 1860, when they ended as an institutional performance, their duration as part of the public and religious records along two hundred and seventy years (1600-1870) gave the opportunity to knowledge droughts in the basin of México. Of the different climatic phenomena, they were the only ones that had the chance to be reliable acknowledge according to the type of information found in Mexico City, since the fundamental mechanism of data, rogation ceremonies, were constantly recorded only during the drought chapters. The rogation ceremonies were carried out with the expectancy of giving end to an environmental or morbid vicissitude. In Mexico City these ceremonies were dedicated, most of the times, to the Virgin of "Los Remedios".

A study of tepetates found in the Glacis de Buenavista, Morelos is hereby presented. The section of study (Ahuatenco) includes a sequence of seven indurate horizons (tepetate layers), underlying a polygenetic and well-developed Luvisol. In this work tepetates are considered as products of erosion-sedimentation and pedogenetic processes. Therefore they are interpreted as paleosols with different degrees of development. Macro and micromorphologic evidences indicate that the tepetate profile is constituted by a mixture of fresh coarse volcanic material, redeposited fragments of soil and pedogenetic features, which include: clay cutans, Fe-Mn nodules, weathered primary minerals and phytoliths accumulated within the layer matrix. These properties show that tepetates were exposed at the surface for a sufficient time to allow pedogenesis. The tepetates parent material are volcanic ashes derived from volcanic events, and eroded Bt-horizon remains from the upper portions that were redeposited along with volcanic materials. Because of the presence of these Bt-horizon fragments the clay content in indurate materials is high (47%), but they display a contrasting distribution, showing lithological and textural discontinuities, so each layer is likely to represent a different stage of landscape evolution. The degree of alteration observed for the different layers vary, as well as the stability periods under which pedogenesis occurs.

This analysis of the geographical space focuses on Geomorphology, a science that deals with the genesis and evolution of landforms. This definition includes two basic elements: relief and form. The former results from geological processes, and the latter from morpho-clilmatic processes. This work derives from the need to communicate the features of landform structures located at the northern portion of the Jalisco state, the main attributes of which including block tectonics, arisen from an extensive area affected by volcanic activity during the Mild Cenozoic. Tectonics respond to core movements generated, according to the pilate tectonics theory, during the Upper Tertiary and Pleistocene, and which have affected this area as a result of the proximity of subduction zones. Lava deposit blocks along with ancient volcanoes have jointly formed wide plateaus denominated riolithic plateaux in the field of structural geomorphology. Landform structures provide the basic element upon which exogenous or morpho-climatic forces work, thus modeling the relief´s sculptural forms. Interfluvial and slope modeling are characterized by the specific dissection of tropical zones; separately, chemical processes originate ferruginous soils and water runoff travels down ravines seeking the water table at the bottom of deep canyons limiting plateaux. Henece edaphogenetic processes dominate at fiat interfluvial areas, whereas displacement of detritic materials prevail along slopes and fluvial terraces at the bottom of valleys.

The study showed that the increase in maximum flows in the watersheds of the left side of the River Papaloapan is due to forest cover clearing on shallow slope areas (less than 6°) in the watersheds of the rivers Obispo, Tesechoacan and San Juan Evangelista. Forest clearing affected from 21 to 43 % of the total area of each watershed during the period 1973-1993. The analysis of annual rainfalls in these watersheds indicated no change in rainfall tendency during 1955-1990.

This article analyzes the conformation and dynamics of a political region in the state of Guanajuato, from electoral geography´s perspective. The case study presented here describes the political system´s elements, namely: territory, society and political actors, and studies the electoral dynamics during the last twenty years, based on data from federal and local elections. As a result, Guanajuato´s political space is typified as an electoral consolidation polo favoring the PAN (National Action Party) political party.

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