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4 resultados encontrados para: AUTOR: Eastman, J. Ronald
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1.
- Artículo con arbitraje
Resumen en: Inglés |
Resumen en inglés

This research examines the spatio-temporal trends in Advanced Very High Resolution Radiometer (AVHRR) Global Inventory Modelling and Mapping Studies (GIMMS) normalized difference vegetation index (NDVI) time series to ascribe land use change and precipitation to observed changes in land cover from 1982 to 2007 in the Mexican Yucatán Peninsula, using seasonal trend analysis (STA). In addition to discrete land cover transitions across the study region, patterns of agricultural intensification, urban expansion and afforestation in protected areas have enacted changes to the seasonal patterns of apparent greenness observed through STA greenness parameters. The results indicate that the seasonal variation in NDVI can be used to distinguish among different land cover transitions, and the primary differences among these transitions were in changes in overall greenness, peak annual greenness and the timing of the growing season. Associations between greenness trends and precipitation were weak, indicating a human-dominated system for the 26 years examined. Changes in the states of Campeche, Quintana Roo and Yucatán appear to be associated with pasture cultivation, urban expansion-extensive cultivation and urban expansion-intensive cultivation, respectively.


2.
- Artículo con arbitraje
A step-wise land-cover classification of the tropical forests of the Southern Yucatán, Mexico
Schmook, Birgit Inge ; Palmer Dickson, Rebecca (coaut.) ; Sangermano, Florencia (coaut.) ; Vadjunec, Jacqueline (coaut.) ; Eastman, J. Ronald (coaut.) ; Rogan, John (coaut.) ;
Contenido en: International Journal of Remote Sensing Vol. 32, no. 4 (February 2011), p. 1139–1164 ISSN: 0143-1161
Resumen en: Inglés |
Resumen en inglés

Analysis of land-cover change in the seasonal tropical forests of the Southern Yucatan, Mexico presents a number of significant challenges for the fine-scale land-cover information required of land-change science. Subtle variation in mature forest types across the regional ecocline is compounded by vegetation transitions following agricultural land uses. Such complex mapping environments require innovation in multispectral classification methodologies. This research presents an application of a step-wise maximum likelihood/In-Process Classification Assessment (IPCA) procedure. This hybrid supervised and unsupervised classification methodology allows for exploration of underlying characteristics of Landsat Thematic Mapper (TM) imagery in tropical environments. Once spectrally separable classes have been identified, field data then determine the ecological definition of vegetation types with special attention paid to areas of unknown or mixed classes. A post-field assessment re-classification using the Dempster-Shafer method reduced the original 25 spectral classes to 14 ecologically distinctive classes, providing the fine-tuned land-cover distinctions that are required for both environmental and socioeconomic research questions. The overall map accuracy was 87% with an average per-class accuracy of 86%. Per-class accuracy ranged from as low as 45% for pasture grass to a high of 100% for tall-stature evergreen upland forest, low and medium-stature semi-deciduous upland forest and deciduous forest.


3.
Capítulo de libro
*En proceso técnico. Solicítelo con el bibliotecario(a) de SIBE-San Cristóbal
Integrated analysis of ecosystem interactions with land-use change:: The southern Yucatán peninsular region
Lawrence, Deborah ; Vester, Henricus F. M. (coaut.) ; Perez Salicrup, D. (coaut.) ; Eastman, J. Ronald (coaut.) ; Turner II, Billie Lee (coaut.) ; Geoghegan, Jacqueline (coaut.) ;
Contenido en: Ecosystem interactions with land use change. Geophysical Monograph Series 153 / R. DeFries, G. Asner, R. Houghton, (eds.) Washington DC., USA. : American Geophysical Union, 2004 p. 277-292
Nota: En proceso técnico. Solicítelo con el bibliotecario(a) de SIBE-San Cristóbal
Resumen en: Inglés |
Resumen en inglés

The southern Yucatán peninsular region is a seasonal tropical forest biome that experiences drought, hurricane, and agricultural disturbance. Substantial agricultural expansion over the past 50 years has opened and fragmented much of the forest surrounding the Calakmul Biosphere Reserve, posing a series of threats to the coupled human-environment systems. These threats are traced in a conceptual model borrowed from vulnerability studies and detailed in regard to ecosystem responses, including forest structure and composition, aboveground biomass, soil nutrients, balance in species and biotic diversity, and invasive species. The land-use and land-cover changes underway pose trade-offs in ecosystem services and raise several scalar issues important to deforestation studies


4.
- Artículo con arbitraje
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Resumen en: Inglés |
Resumen en inglés

The southern Yucatán contains the largest expanse of seasonal tropical forests remaining in Mexico, forming an ecocline between the drier north of the peninsula and the humid Petén, Guatemala. The Calakmul Biosphere Reserve resides in the center of this region as part of the Mesoamerican Biological Corridor. The reserve’s functions are examined in regard to land changes throughout the region, generated over the last 40 years by increasing settlement and the expansion and intensification of agriculture. These changes are documented from 1987/1988 to 2000, and their implications regarding the capacity of the reserve to protect the ecocline, forest habitats, and butterfly diversity are addressed. The results indicate that the current landscape matrix serves the biotic diversity of the reserve, with several looming caveats involving the loss of humid forests and the interruption of biota flow across the ecocline, and the amount and proximity of older forest patches beyond the reserve. The highly dynamic land cover changes underway in this economic frontier warrant an adaptive management approach that monitors the major changes underway in mature forest types, while the paucity of systematic ecological and environment–development studies is rectified in order to inform policy and practice.