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25 resultados encontrados para: AUTOR: Vaca, Raúl
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Applicability of biodiversity databases to regional conservation planning in the tropics: a case study evaluation of the effect of environmental bias on the performance of predictive models of species richness
Vaca Genuit, Raúl Abel (autor) ; Rodiles Hernández, María del Rocío (autora) (1956-) ; Soria Barreto, Miriam (autora) ; Muñoz Alonso, Luis Antonio (autor) ; González Díaz, Alfonso Ángel (autor) ; Castillo Santiago, Miguel Ángel (autor) ;
Disponible en línea
Contenido en: Acta Oecologica Volumen 109, artículo número 103653 (November 2020), páginas 1-13 ISSN: 1146-609X
Nota: Solicítelo con su bibliotecario/a
Resumen en: Inglés |
Resumen en inglés

The biodiversity data typically available for fitting distributional models in the tropics come from museum and scientific collections which are often incomplete and prone to sampling and environmental biases. Nevertheless, most studies undertaken in tropical regions assume that collection data offers a satisfactory environmental coverage without any quantitative assessment. In this study, we investigate the effects of differences in environmental bias and coverage provided by distributional data when aggregated into different grid cell sizes, on the performance of species richness-environment models and predictions. We use an extensive data compilation, including national and regional collections, on the distribution of amphibians, reptiles and fishes in the hydrologic region of the Usumacinta River as a case study. General additive models and environmental variables are used to construct predictive models at 40, 20, 10 and 5 km grid resolutions, based on well-sampled cells. The best multivariate models included nonparametric interaction terms for the effects of precipitation and temperature and suggested an altitudinal shift in the relative importance of energy and water in determining the distribution of species richness.

For fishes, geomorphology accounted for fine scale variation in species richness along the hydrologic network, indicated by peaks in species diversity at the junction of the major rivers where major accumulation of water and sediments occurs. For all taxonomic groups, we found that sampling biases deviated most from the mean bias at the extremes of gradients accounting for important environmental factors. The pattern of environmental bias changed with grid size, with the form and amount of change being casespecific. Biases affected distribution predictions when compared with unbiased datasets. Moreover, not all models resulted best at coarser resolution as it is commonly assumed. Our results demonstrate that bias in the available data must be evaluated before mapping biodiversity distributions, irrespective of the choice of scale.

Resumen en: Inglés |
Resumen en inglés

Background: Reliable information about the spatial distribution of aboveground biomass (AGB) in tropical forests is fundamental for climate change mitigation and for maintaining carbon stocks. Recent AGB maps at continental and national scales have shown large uncertainties, particularly in tropical areas with high AGB values. Errors in AGB maps are linked to the quality of plot data used to calibrate remote sensing products, and the ability of radar data to map high AGB forest. Here we suggest an approach to improve the accuracy of AGB maps and test this approach with a case study of the tropical forests of the Yucatan peninsula, where the accuracy of AGB mapping is lower than other forest types in Mexico. To reduce the errors in field data, National Forest Inventory (NFI) plots were corrected to consider small trees. Temporal differences between NFI plots and imagery acquisition were addressed by considering biomass changes over time. To overcome issues related to saturation of radar backscatter, we incorporate radar texture metrics and climate data to improve the accuracy of AGB maps. Finally, we increased the number of sampling plots using biomass estimates derived from LiDAR data to assess if increasing sample size could improve the accuracy of AGB estimates.

Results: Correcting NFI plot data for both small trees and temporal differences between field and remotely sensed measurements reduced the relative error of biomass estimates by 12.2%. Using a machine learning algorithm, Random Forest, with corrected field plot data, backscatter and surface texture from the L‑band synthetic aperture radar (PALSAR) installed on the on the Advanced Land Observing Satellite‑1 (ALOS), and climatic water deficit data improved the accuracy of the maps obtained in this study as compared to previous studies (R²=0.44 vs R²= 0.32). However, using sample plots derived from LiDAR data to increase sample size did not improve accuracy of AGB maps (R²= 0.26). Conclusions: This study reveals that the suggested approach has the potential to improve AGB maps of tropical dry forests and shows predictors of AGB that should be considered in future studies. Our results highlight the importance of using ecological knowledge to correct errors associated with both the plot‑level biomass estimates and the mis‑match between field and remotely sensed data.

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

There is increasing recognition that ecosystems and their services need to be managed at landscape scale and greater. The development of landscape-scale conservation strategies need to incorporate information from multiple sources. In this study, we combine various research tools to link landscape patterns with production units and systems in the Usumacinta River Basin, and inform the discussion of key questions around decisionmaking related to conservation action and policy in Southern Mexico. A typology based on policy-relevant farmer characteristics (land tenure, farm size, source of income, farming system) differentiated between farmers (traditional vs. cattle ranching) with different motivations that determine how management affects landscape configuration. Five main types of traditional farming systems were identified that combine different forms of land use and vary in their degree of land intensification. Major fragmentation and decrease in connectivity coincided spatially with floodplains dominated by large-scale commercial farms that specialize in livestock production.

Traditional practices within large units with low-sloped high quality land were also seen to be intensive; however the presence of trees was notable throughout these units. Policies that promote livestock farming are among the principle causes motivating deforestation. Land intensification by traditional farmers decreased as the landscape became increasingly rugged. Traditional farmers are the focus of initiatives developed by the Biological Corridor project which seeks to increase forest cover and landscape connectivity. These initiatives have shown high levels of rural participation (10,010 farmers benefited from 27,778 projects involving 95,374 ha of land) and acceptance (producers carried out more than one project and several types of projects during the first eight years of work). Strong action is still required to take on the segment of large-scale ranchers. Changes in the structure of land tenure over the past decade are highlighted that could have a profound impact on conservation policies and programs.

- Artículo con arbitraje
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Polycultures, pastures and monocultures: effects of land use intensity on wild bee diversity in tropical landscapes of southeastern Mexico
Vides Borrell, Eric (autor) ; Porter Bolland, Luciana (autora) ; Ferguson, Bruce G. (autor) (1967-) ; Gasselin, Pierre (autor) ; Vaca Genuit, Raúl Abel (autor) ; Valle Mora, Javier Francisco (autor) ; Vandame, Rémy (autor) ;
Contenido en: Biological Conservation Vol. 236 (August 2019), p. 269-280 ISSN: 0006-3207
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Resumen en: Inglés |
Resumen en inglés

The conservation of pollinator diversity is fundamental to maintaining sustainable agricultural systems and food security. Some agricultural systems support pollinator diversity, while others may lead to their decline. Previous studies have evaluated the impacts of agricultural intensification on pollinators in temperate climates regions, but in tropical regions these impacts have been evaluated by only very few studies. We conducted a study in southeastern Mexico, in order to understand the effects of three agricultural systems on bee diversity in a tropical landscape. We compared 18 sites at two different scales (plot scale and landscape scale). We found a link between agricultural system intensity level at the plot scale and forest proportion at the landscape scale: land use intensity was low at both scales in 7 polycultures, low at plot scale and high at landscape scale in 4 pastures, and high at both scales in 7 monocultures. We collected bees at all sites, and found an overall high bee richness, with a total of 127 species. Bee richness was compared across agricultural systems using diversity accumulation curves with iNEXT package. Both polycultures and pastures had significantly higher richness as monocultures. We constructed bee species guilds according to ecological and life-history traits (i.e. size, sociality and nesting) and found that whatever the trait considered, the species richness in the different agricultural systems was most often affected in the same way than the complete community richness.

Our results show, for the first time in tropical conditions that agricultural systems with low-intensity farming practices and forested landscape allow the preservation of a significantly higher diversity of bees than agricultural systems with high-intensity farming practices and highly deforested landscape. Considering that bee diversity is key to maintaining crop productivity, these findings can help scientists, policy-makers, and community members design policies that support both agricultural production and biodiversity conservation in the tropics.

- Artículo con arbitraje
A 6-year longitudinal study on agrobiodiversity change in homegardens in Tabasco, México
Serrano Ysunza, Andrea Alejandra ; Van Der Wal, Hans (coaut.) ; Gallardo Cruz, José Alberto (coaut.) ; Ramos Muñoz, Dora Elia (coaut.) ; Vaca Genuit, Raúl Abel (coaut.) ;
Contenido en: Agroforestry Systems Vol. 92, no. 6 (December 2018) p. 1485-1494 ISSN: 1572-9680
Resumen en: Inglés |
Resumen en inglés

Societal processes of rural change and globalization may change homegardens and their contribution to the conservation of agrobiodiversity, particularly of species occurring naturally in regional vegetation. The best way to determine if this occurs is through longitudinal studies. We conducted such a study, inventorying tree species in a sample of 38 homegardens in 2009, 2012 and 2015. The homegardens were located in the subregions of mountain slopes, fluvial plains and coastal plains in the tropical lowlands of Tabasco, Mexico. We analysed changes in species richness by geographic origin, species richness and species composition in each inventory. We identified 169 tree species in the three inventories, of which 74.6% were native or neotropical and 25.4% introduced. Of the 140 species recorded in 2009, 88% remained in 2015, whereas 12% had been replaced and nine additional species had arrived. Mean species richness increased between 2009 and 2015 (P = 0.03) and between 2012 and 2015 (P = 0.001). Increases resulted from increased mean neotropical (P = 0.01) and introduced (P = 0.01) species richness, and constant native species richness. Differences in species composition between the three subregions in 2009 persisted in 2012 and 2015 (P\0.001 in all years). These results show how the highly dynamic character of homegardens combines with the renewal and persistence of their agrobiodiversity, andunderpins the continued relevance of homegarden for agrobiodiversity conservation and livelihoods in tropical lowlands amidst rural change and globalization.

Resumen en: Inglés |
Resumen en inglés

Quantifying patterns of deforestation and linking these patterns to potentially influencing variables is a key component of modelling and projecting land use change. Statistical methods based on null hypothesis testing are only partially successful for interpreting deforestation in the context of the processes that have led to their formation. Simplifications of cause-consequence relationships that are difficult to support empirically may influence environment and development policies because they suggest simple solutions to complex problems. Deforestation is a complex process driven by multiple proximate and underlying factors and a range of scales. In this study we use a multivariate statistical analysis to provide contextual explanation for deforestation in the Usumacinta River Basin based on partial pattern matching. Our approach avoided testing trivial null hypotheses of lack of association and investigated the strength and form of the response to drivers. As not all factors involved in deforestation are easily mapped as GIS layers, analytical challenges arise due to lack of a one to one correspondence between mappable attributes and drivers. We avoided testing simple statistical hypotheses such as the detectability of a significant linear relationship between deforestation and proximity to roads or water.

We developed a series of informative generalised additive models based on combinations of layers that corresponded to hypotheses regarding processes. The importance of the variables representing accessibility was emphasised by the analysis. We provide evidence that land tenure is a critical factor in shaping the decision to deforest and that direct beam insolation has an effect associated with fire frequency and intensity. The effect of winter insolation was found to have many applied implications for land management. The methodology was useful for interpreting the relative importance of sets of variables representing drivers of deforestation. It was an informative approach, thus allowing the construction of a comprehensive understanding of its causes.

- Capítulo de libro con arbitraje
Evaluación de servicios ambientales hidrológicos en subcuencas del Área Natural Protegida La Frailescana
Escamilla Rivera, Verenice Isabel ; Cortina Villar, Héctor Sergio (coaut.) (1960-) ; Golicher, Duncan John (coaut.) ; Vaca Genuit, Raúl Abel (coaut.) ; Arellano Monterrosas, José Luis Leobardo (coaut.) ;
Contenido en: Suelos de Chiapas: manejo, conservación y restauración Tuxtla, Gutiérrez, México: Universidad Autónoma de Chiapas, 2017 p. 135-157 ISBN:978-607-8459-59-9

Tesis - Doctorado
Resumen en español

La demanda de la población sobre los ecosistemas está creciendo y ejerciendo presión sobre los servicios ambientales hidrológicos de cuencas tropicales, como es la cantidad de agua y la regulación de las aguas de superficie y subterránea. Aunque, puede parecer que los bosques absorben el agua disponible, dejando menos cantidad para el uso humano. Una revisión de literatura sobre la relación bosque- agua en cuencas tropicales deja ver que esta relación es más compleja, y que los servicios hidrológicos de provisión y regulación que se comercializan en los esquemas de Pagos por Servicios Ambientales (PSA) normalmente no se cuantifican de manera adecuada, aunque se aceptan de forma pragmática. En esta tesis se evaluó la cantidad y regulación del agua en cuencas donde se ha concedido el PSA. Primero se analizó si las predicciones del caudal mejoran al utilizar datos de suelos y vegetación disponibles al público vs datos finos. Luego se analizó cómo la deforestación que ocurrió en la cuenca afectó el caudal y el flujo hídrico base, y cuál hubiera sido el impacto si continuara la deforestación. Por último, aunque el modelo SWAT es una herramienta que ayuda en la cuantificación de los servicios hidrológicos, se realizó una revisión sistemática de la literatura para conocer el alcance del modelo en la simulación y predicción de las alteraciones en los regímenes hidrológicos. Esfuerzos adicionales se realizaron para entender la relación bosque-agua, como son la exploración del comportamiento hidrológico a escalas de cuencas en la modelación SWAT y la medición de lluvia-escurrimiento en cuencas pareadas.


Capítulo I.
1.1 Entendiendo los servicios ambientales hidrológicos de los bosques
1.2 Investigación futura de la relación bosque-agua
1.3 ANP La Frailescana: Escenario para la evaluación de servicios ambientales hidrológicos
Capítulo II.
Effects of finer scale soil survey and land-use classification on SWAT hydrological modelling accuracy in data-poor study areas
Capítulo III.
Modelando el impacto de la deforestación en la hidrología de áreas de conservación forestal
. Capítulo IV.
Modeling hydrological regimes with the Soil and Water Assessment Tool (SWAT): from systematic review to scientific debate
Capítulo V.
Conclusiones generales
I. Evaluación de servicios ambientales hidrológicos en subcuencas del Área Natural Protegida La Frailescana
II. Mediciones de lluvia-escorrentía en cuencas pareadas

Tesis - Maestría
Análisis del cambio del uso del suelo y cobertura en el Soconusco, Chiapas / Rosa Elena Escobar Flores
Escobar Flores, Rosa Elena (autora) ; Castillo Santiago, Miguel Ángel (director) ; Navarrete Gutiérrez, Darío Alejandro (asesor) ; Vaca Genuit, Raúl Abel (asesor) ;
San Cristóbal de Las Casas, Chiapas, México : El Colegio de la Frontera Sur , 2016
Disponible en línea
Clasificación: TE/631.47097275 / E8
SIBE Campeche
ECO040006489 (Disponible)
Disponibles para prestamo: 1
SIBE Chetumal
ECO030008548 (Disponible)
Disponibles para prestamo: 1
SIBE San Cristóbal
ECO010018386 (Disponible)
Disponibles para prestamo: 1
SIBE Tapachula
ECO020013566 (Disponible)
Disponibles para prestamo: 1
SIBE Villahermosa
ECO050006167 (Disponible)
Disponibles para prestamo: 1

Siglas Utilizadas
Estructura y Composición de la Tesis
Capítulo 1. Introducción
1.1 Cambio en la cobertura y uso de suelo
1.2. Disponibilidad de cartografía para la zona de estudio
1.3. Información estadística socioeconómica básica
1.4. Interpretación y análisis de imágenes de satélite
1.5. Antecedentes de la zona de estudio
1.6 Preguntas de investigación
1.7. Objetivo General
1.7.1 Objetivos específicos
Capítulo 2. Artículo sometido
Capítulo 3. Discusión General
3.1 Procesos de cambio en la cobertura y uso de suelo en la zona de estudio
3.2 Factores indirectos del cambio de uso de suelo en el área de estudio
Literatura citada en los capítulos de introducción y consideraciones finales
Anexo 1
Anexo 2 Formato de Campo
Anexo 3 Fotografías

Tesis - Maestría
Cambios espacio-temporales en la agrobiodiversidad de los huertos familiares de Tabasco / Andrea Alejandra Serrano Ysunza
Serrano Ysunza, Andrea Alejandra ; Van Der Wal, Hans (director) ; Gallardo Cruz, José Alberto (co-director) ; Ramos Muñoz, Dora Elia (asesora) ; Vaca Genuit, Raúl Abel (asesor) ;
Villahermosa, Tabasco, México : El Colegio de la Frontera Sur , 2016
Clasificación: TE/635.097263 / S4
Bibliotecas: Villahermosa
SIBE Villahermosa
ECO050006072 (Disponible)
Disponibles para prestamo: 1
Índice | Resumen en: Español |
Resumen en español

La agrobiodiversidad en agroecosistemas tropicales como huertos familiares se encuentra bajo presión, principalmente por la preferencia por cultivar especies comerciales. Consecuentemente, los huertos podrían dejar de contribuir a la conservación in situ de especies locales. Existen pocos estudios longitudinales y consenso general sobre los cambios, la disminución u homogenización de especies. Este trabajo es un estudio longitudinal regional de los cambios en abundancia, riqueza y composición en 38 huertos distribuidos sobre las subregiones de Costa, Planicie Fluvial y Montaña en Tabasco, México. Se analizó información de tres inventarios realizados en 2009, 2012 y 2015. Se identificaron 164 especies (74.39 % especies locales -nativas y neotropicales- y 25.61 % introducidas). Del total, 67 % se mantuvieron constantes y el 33 % se modificaron a lo largo de los años de medición. La riqueza observada aumentó significativamente (χ2(2)=9.021, P=0.01) de 2012 a 2015 (P = 0.004).

En ese lapso incrementaron las especies neotropicales (χ2(2)=10.25, P =0.024) e introducidas (χ2(2)=6.96, P=0.008) y se mantuvo la riqueza de nativas. La composición de especies difirió subregionalmente en 2009 (R=0.19, P=0.001) y persistió en 2012 y 2015 (P=0.003 y 0.0001). La riqueza de especies observada se correlaciona positivamente con el número de árboles (r=0.79, P<0.001) y el tamaño del huerto (r= 0.67, P< 0.001). No se detectó que los índices de inclusión del huerto en la Economía Familiar y del Trabajo Evidente realizado, se relacionaran con la riqueza de especies o el número de árboles. Resalta que los conjuntos subregionales muestran tasas de cambio similares y sin disminución de riqueza de ningún tipo de especies. Los huertos familiares individualmente son altamente dinámicos, sin embargo, esto no involucra disminución en la riqueza de especies a escala subregional o regional. Consider los conjuntos subregionales sugiere que operan como conjuntos de conservación de agrobiodiversidad regional in situ.


1. Resumen
2. Introducción
3. Antecedentes
3.1. Situación agrícola y pérdida de biodiversidad
3.2. El paisaje agrícola de Tabasco
3.3. Agroecosistemas a escala local
3.4. Huertos Familiares
3.5. Agroecosistemas de conservación de agrobiodiversidad
3.6. Rol de los propietarios en la conservación
4. Justificación
5. Preguntas de investigación
6. Objetivo general y particulares
7. Metodología
7.1. Zona de estudio
7.2. Selección de huertos
7.3. Determinación de cambios
7.4. Construcción de índices
7.5. Análisis de datos
8. Resultados
8.1. Composición de los huertos familiares en 2009, 2012 y 2015
8.2. Cambios en el número de árboles y recambio de especies a escala regional
8.3. Diferencias y cambios subregionales de la agrobiodiversidad
8.4. Índices de Economía Familiar y Trabajo Evidente
9. Discusión
10. Conclusión
11. Literatura citada
Anexo 1. Lista de especies y origen biogeográfico
Anexo 2. Número de árboles y Riqueza de especies en los tres inventarios
Anexo 3. Encuesta “Cambios en la agrobiodiversidad en función de la productividad de los huertos familiares”
Anexo 4. Construcción de los índices de Economía Familiar y Trabajo Evidente
Anexo 5. Artículo sometido a la revista Agroforestry Systems