Search

Tropical montane cloud forests (TMCF) are threatened ecosystems despite their capacity to maintain high dry-season baseflow. A number of conservation policies, including payments for hydrological services, have been implemented to protect these forests. However, since most of the modeling tools used to assess the impacts of these policies were developed for temperate zones, more work is needed to understand and improve the applicability of popular models in tropical contexts. This study uses local evapotranspiration and streamflow datasets to calibrate and validate an improved version of the Soil and Water Assessment Tool model for the Tropics (SWAT-T). Vegetation growth and canopy water storage capacity were calibrated using field data. Three methods provided by SWAT-T to calculate potential evapotranspiration (PET) were compared: Penman-Monteith (SWAT-T-PM), Hargreaves (SWAT-T-HA), and Priestly-Taylor (SWAT-T-PT). Sensitivity analysis and calibration of daily streamflow were conducted at the catchment scale (34 km2). Furthermore, the calibrated models were validated at three sites with evapotranspiration data, and at four distinct micro-catchments (0.137–0.446 km2) with gauged streamflow data. Overall, SWAT-T satisfactorily simulated streamflow during the calibration period producing acceptable goodness of fit indices. However, the model incorrectly predicted the dominance of lateral flow instead of the deep groundwater flow observed from isotope-based studies. SWAT-T-HA performed better than SWAT-T-PM and SWAT-T-PT, but all models underestimated the influence of rainfall interception losses since evaporation is limited by daily PET in forests. Finally, SWAT-T largely over- and underestimated mean annual daily low flow in pastures and forests, respectively. Taken together, these results indicate that improvements in the parametrization of rainfall interception and deep subsurface flow dynamics in SWAT-T are required to improve applicability of this modeling tool in tropical montane areas underlain by permeable substrates.

Background: Explored botanically from the 19th century, the Sierra de Chiconquiaco is recognized for its large vegetal and topographical heterogeneity. However, the available floristic information is sparse and its geographic characteristics remain undefined. The objective of this study was therefore to integrate floristic, vegetal and geographic information in order to identify areas that have experienced floristic exploration as well as potential sites for conservation. Question: Under which criteria can the Sierra be geographically delimited? What kind of floristic and vegetational studies have been carried out? How many species of plants have been registered? Which sites have been more widely explored? Which of them have conservation and research potentials? Study site and years of study: Sierra de Chiconquiaco, Veracruz, Mexico, 2010-2014. Methods: A bibliographical and records review of the XAL and MEXU herbariums, works and field survey were carried out. Through analysis of geomorphological attributes in a geographic information system, the boundaries of the Sierra were established, revealing an area of 3,632 km2, featuring 22 municipalities and an altitudinal range of 50 to 3,000 m a.s.l. Results: Seven vegetation types were described, as well as a floristic list of 3,019 species, including 72 type localities, 36 endemics, 57 registered in the NOM-059, 2010 and 195 in the CITES. Conclusions: Nine potential areas for conservation of flora were detected, as well as six that were scarcely documented in the herbaria. This study provides a relevant contribution to the knowledge, use and conservation of the vegetal resources of Mexico.

Stream water mean transit time (MTT) is a fundamental hydrologic parameter that integrates the distribution of sources, flow paths, and storages present in catchments. However, in the tropics little MTT work has been carried out, despite its usefulness for providing important information on watershed functioning at different spatial scales in (largely) ungauged basins. In particular, very few studies have quantified stream MTTs or have related these to catchment characteristics in tropical montane regions. Here we examined topographic, land use/cover and soil hydraulic controls on baseflow transit times for nested catchments (0.1–34 km2) within a humid mountainous region, underlain by volcanic soil (Andisols) in central Veracruz (eastern Mexico). We used a 2-year record of bi-weekly isotopic composition of precipitation and stream baseflow data to estimate MTT. Land use/cover and topographic parameters (catchment area and form, drainage density, slope gradient and length) were derived from geographic information system (GIS) analysis. Soil water retention characteristics, and depth and permeability of the soil–bedrock interface were obtained from intensive field measurements and laboratory analysis. Results showed that baseflow MTTs ranged between 1.2 and 2.7 years across the 12 study catchments. Overall, MTTs across scales were mainly controlled by catchment slope and the permeability observed at the soil–bedrock interface. In association with topography, catchment form and the depth to the soil–bedrock interface were also identified as important features influencing baseflow MTTs. The greatest differences in MTTs were found both within groups of small (0.1–1.5 km2) and large (14–34 km2) catchments. Interestingly, the longest stream MTTs were found in the headwater cloud forest catchments.

La provision y regulacion de flujos de agua en cuencas es probablemente el servicio ecosistemico mas importante de los bosques de niebla, sin embargo, su funcionamiento hidrologico y como este es alterado por el cambio en el uso de suelo es aun muy poco entendido. Este estudio evaluo los efectos hidrologicos causados por la conversion del bosque mesofilo de montana sobre suelo volcanico a otros tipos de vegetacion en Veracruz, Mexico. Para ello, se realizaron mediciones micrometeorologicas, ecofisiologicas e hidrologicas combinadas con informacion isotopica. Los resultados mostraron mayores rendimientos hidricos anuales en el pastizal y plantaciones de Pinus patula joven y maduro debido a menores tasas de evapotranspiracion comparados con el bosque maduro y secundario. El caudal total anual y estacional fue similar en los bosques, sugiriendo que con 20 anos de regeneracion natural es posible restaurar la funcionalidad hidrologica de microcuencas. En contraste, la microcuenca de pastizal reporto un mayor caudal anual (10 %), pero flujos 50 % en promedio mas bajos al final de la epoca de estiaje, asociado probablemente a una topografia mas suave y una menor capacidad de infiltracion. Aun en sustratos volcanicos altamente permeables, se observo que la conversion de bosque a pastizal puede conducir a incrementos importantes en los flujos superficiales en respuesta a eventos maximos de precipitacion. El efecto de la reforestacion con P. patula a escala de cuenca se desconoce, pero tasas de infiltracion mas altas que el pastizal sugieren una probable recuperacion hidrica del suelo en el corto a mediano plazo.

Key message Highly variable nighttime transpiration, with higher rates generally observed after preceding fog, is prevalent in dominant tree species of the nutri- ent-poor tropical montane cloud forest environment of central Veracruz, Mexico. Abstract Although nighttime transpiration (En) is pre- valent in a wide range of species from cloud-affected for- ests, its magnitude relative to total daily transpiration (Ed) as reported in the literature is generally small (En/Ed is 0.12 on average). In the present study, we observed high dry- season En/Ed ratios with large night-to-night variation in dominant species from the tropical montane cloud forest (TMCF) zone of central Veracruz, Mexico: 0.22 ± 0.18 for Quercus lancifolia (old-growth TMCF); 0.26 ± 0.14 and 0.16 ± 0.16 for Alchornea latifolia and Alnus jorull- ensis, respectively (regenerating post-fire TMCF); and 0.30 ± 0.20 to 0.12 ± 0.21 for Pinus patula (young and mature pine plantations). En was determined as the dif- ference between observed nocturnal sap flow and estimated refilling of stem water storage, the latter of which was on average: 21-25 % of nocturnal sap flow for Q. lancifolia ;6 and 5 % for A. latifolia and A. jorullensis, respectively; and 21-23 % for P. patula. Night-to-night variation in En was mostly due to large variation in vapor pressure deficit (VPD) related in turn to the alternation of cold fronts (producing fog events) and high pressure weather (pro- ducing nights with VPD up to 2 kPa). Moreover, in the hours following fog events without concurring rainfall, En was often higher as compared to fog-free nights with similar VPD across all species examined. Low-nutrient availability and high water content of the soils in the study area suggest a nutrient uptake benefit associated with the relatively high En rates observed.

Payment for hydrological services (PHS) are popular tools for conserving ecosystems and their water-related services. However, improving the spatial targeting and impacts of PHS, as well as their ability to foster synergies with other ecosystem services (ES), remain challenging. We aimed at using spatial analyses to evaluate the targeting performance of México's National PHS program in central Veracruz. We quantified the effectiveness of areas targeted for PHS in actually covering areas of high HS provision and social priority during 2003-2013. First, we quantified provisioning and spatial distributions of two target (water yield and soil retention), and one non-target ES (carbon storage) using InVEST. Subsequently, pairwise relationships among ES were quantified by using spatial correlation and overlap analyses. Finally, we evaluated targeting by: (i) prioritizing areas of individual and overlapping ES; (ii) quantifying spatial co-occurrences of these priority areas with those targeted by PHS; (iii) evaluating the extent to which PHS directly contribute to HS delivery; and (iv), testing if PHS targeted areas disproportionately covered areas with high ecological and social priority. We found that modelled priority areas exhibited non-random distributions and distinct spatial patterns. Our results show significant pairwise correlations between all ES suggesting synergistic relationships. However, our analysis showed a significantly lower overlap than expected and thus significant mismatches between PHS targeted areas and all types of priority areas. These findings suggest that the targeting of areas with high HS provisioning and social priority by Mexico's PHS program could be improved significantly. This study underscores: (1) the importance of using maps of HS provisioning as main targeting criteria in PHS design to channel payments towards areas that require future conservation, and (2) the need for future research that helps balance ecological and socioeconomic targeting criteria.

In the montane grasslands of Mexico, perennial grass and black Andisols are linked in a complex mechanism of soil formation in which both biogenic and mineral products interact. In this ecosystem, typical of the volcanic highlands, a sequence of profiles has been studied by macro- and micro-morphology, scanning and transmission electron microscopy (TEM), infra-red spectroscopy of soil samples and humic acid (HA) extracts, radiocarbon dating and pollen record, soil moisture and available water determinations and soil water analyses. The grass Muhlennberrgia macroura is important in the soil-forming process as it is the host of micro- and meso-fauna which produce abundant organic micro-aggregates. Soil formation began 7550 years ago and continued through several climatic and vegetation changes. The soil thickens as its age increases. Mineral neoformation is oriented towards allophane and halloysite, rather than Al-rich minerals such as imogolite and gibbsite, and high Si contents are observed in the soil water. The black Andisols have high water and carbon storage capacities and play a prominent role in regulating drainage. Presentday destruction of the grassland for potato cultivation will decrease the waterer reserve of these volcanic highlands.

Weathering and neoformation of allophane, imogolite and halloysite in volcanic ash soils have been studied extensively in humid climates but little data are available on these soils in arid and semi-arid conditions. Weathering and soil formation under semi-arid conditions on acid pyroclastics have been investigated in two profiles, both at the micro-site scale and on bulk samples. XR microdiffraction and SEM-EDX microanalysis were performed on soil thin sections. Chemical, particle-size, XRD and mineral identification analysis were performed on conventional soil samples. Results show the interplay of various sub-processes : intense division of the coarse minerals into small fragments 50-200 micrometers in size ; diagenesis of noncrystalline products in the zone of contact with the parent minerals ; transformation of noncrystalline minerals into halloysite in the compact soil microstructures and preservation of the noncrystalline minerals in the topsoil ; desiccation and condensation of the crystalline and noncrystalline minerals into microaggregates in the topsoil. The results of these interacting weathering processes are silty-loam soils with no cohesion and high susceptibility to wind erosion. Differences appearing between different analytical methods at different sampling scales need special precautions in explaining the results. (Résumé d'auteur)

La palma camedor es una planta or na men tal que ha sido recolectada en las regiones tropicales de México y actualmente también es cultivada en varios estados del país, es una planta umbrófila que puede estar integrada en sistemas de producción que cuentan con un estrato arbóreo. Debido a la importancia que tiene esta especie en los programas que se enfocan a promover el manejo de los recursos naturales, se planteó identificar su perfil biofísico con miras a apoyar la planificación de su cultivo, aprovechamiento y conservación. La metodología consistió en la generación de una base de datos referida a los sitios en que se encuentra la especie y en un sistema de información geográfica en el que se identificaron los intervalos de las principales vari ables ambientales donde se distribuye. El perfil biofísico de palma camedor se presenta en términos de cinco vari ables climáticas, cuatro geomorfológicas, tres edafológicas y una lista de tipos de vegetación y sistemas de producción.

El entendimiento de los procesos ecosistémicos y la búsqueda de consensos entre actores son fundamentales para el mantenimiento de los servicios ecosistémicos. Presentamos un ejercicio de modelación mediada sobre el funcionamiento hidrológico de un bosque mesófilo de montaña y se analiza si favorece la comprensión, el análisis y la búsqueda de consensos entre investigadores de distintas disciplinas.

Ante el deterioro de los recursos naturales en zonas tropicales, los sistemas agroforestales han sido identificados como técnicas de manejo de la tierra que permiten una producción más sostenible. Por otra parte, las metodologías de zonificación agroecológica ayudan a ubicar aquellos tipos de uso del suelo que se ajustan mejor a las características físicas de una región. Sin embargo, aún no hay experiencias de zonificación agroecológica en sistemas agroforestales. En este trabajo se presenta una propuesta tomando como modelo al sistema café-palma camedor. La propuesta se basa en selección y categorización de variables ambientales, la construcción del modelo cartográfico y la síntesis cartográfica y validación. En el mapa de zonificación agroecológica se ubican los diferentes niveles de aptitud que se presentan en el área de estudio para este sistema, determinándose que 85,5% del área presenta restricciones ambientales. En la validación se utilizaron datos de distribución del sistema agroforestal y mediante la generación de modelos lineales generalizados se estimó el efecto que tienen las variables ambientales en su distribución. De las 11 variables solo la temperatura mínima (palma), la pedregosidad y la fertilidad del suelo no tuvieron significación estadística (P>0,05). Con los modelos lineales se elaboraron mapas de probabilidad de presencia del sistema agroforestal; en el aspecto climático se registró un coeficiente de determinación de 0,70 y en el ámbito edafológico de 0,45. Se realizaron análisis de correlación entre los mapas de aptitud y los mapas de presencia del sistema agroforestal, registrándose solo correspondencia en el aspecto climático (r= -0,88). In view of the deterioration of the natural resources in tropical areas, agroforestry systems have been identified as land management techniques that allow for a more sustainable production. On the other hand, methods of agro-ecological zoning help locate those types of land use better suited to the physical characteristics of a region. However, agro-ecological zoning has not been developed yet for agroforestry systems. In this work, such a proposal is developed, taking as a case study the coffee-parlor palm system. This proposal is based on selection and categorization of environmental variables, construction of a cartographic model, cartographic synthesis and validation. In a map of agro-ecological zoning, the different suitability levels present in the study area are located. It was determined that 85.5% of the area has environmental constraints. Data for agroforestry system distribution are used for the validation process and, by means of generalized linear models, the effect of environmental variables on this distribution was assessed. Of the 11 variables, only minimum temperature (palm), stone abundance and soil fertility didn’t have statistical significance (P>0.05). With the linear models, maps of presence probability were generated. A determination coefficient of 0.70 for the climatic factor and of 0.45 for the edaphic component, were registered. Correlation analysis was carried out between the suitability maps and the presence maps of the agroforestry system, registering correspondence only in the climatic aspect (r= -0.88). Diante ao deterioro dos recursos naturais nas zonas tropicais se têm identificados aos sistemas agroforestais como técnicas de manejo da terra que permitem uma produção mais sostenível. Por outra parte, as metodologias sob zonificação agroecológica ajudam a ubicar aqueles tipos de usos do solo que ajustam-se melhor às características físicas de uma região. A zonificação agroecológica destes sistemas é um aspecto não desenvolvido, pelo que neste trabalho se apresenta uma proposta levando como modelo ao sistema cafeeiro-palmeira camedor. A proposta baseia-se na seleção e caracterização de variáveis ambientais, construção do modelo cartográfico, síntese cartográfica e validação. No mapa de zonificação agroecológica se localizam os diferentes graus de atitude que se apresentam na área de estudo para este sistema, determinando que no 85,5% da área apresenta restrições ambientais. Na validação se utilizarão dados de distribuição do sistema agroforestal e pela geração de modelos lineais generalizados se estimou o efeito que tem as variáveis ambientais em seu distribuição. Das onze variáveis só a temperatura mínima (palmeira), pedregosidade e a fertilidade do solo não apresentaram significância estatística (P>0,05). Com os modelos lineais se elaborou mapas de possibilidade da presença do sistema agroforestal, no aspecto climático registro-se um coeficiente de determinação de 0,70 e no âmbito do solo de 0,45. Realizou-se o analise de correlação entre os mapas de atitude com os mapas da presença do sistema agroforestal, registrando correspondência só no aspecto climático (r=-0,88).

"La estructura del suelo de los terrenos forestales o de pastizal convertidos a cultivo sufre una significativa modificación. En México, los suelos de origen volcánico de zonas sub-húmedas, deforestados y sometidos a un uso agrícola continuo, padecen a menudo procesos dedegradación. El objetivo de este estudio fue determinar la agregación del suelo en Andisoles de uso forestal y cultivados del Cofre de Perote (Veracruz), a fin de establecer la vulnerabilidad de su estructura al impacto de los cambios de uso del suelo. La distribución por tamaño y la estabilidad de agregados en agua se obtuvieron en horizontes en seis Udivitrands, mediante el método de tamizado en húmedo. Los horizontes superficiales forestales presentan una estructura más estable que los cultivados. La pérdida de la estabilidad de los agregados en suelos cultivados se correlacionó con la disminución de la materia orgánica y con el aumento de los microagregados (< 0 25 mm) respecto a los macroagregados (> 2.0 mm); sin embargo, la disminución de la estabilidad estructural después de 50 años de cultivo es sólo moderada. Las principales consecuencias de la degradación de la estructura fueron la pérdida de nitrógeno y la reducción de la retención en agua a capacidad de campo y al punto de marchitez permanente. La distribución por tamaño y la estabilidad de los agregados en agua son parámetros útiles para evaluar la calidad de la estructura en Andisoles forestales convertidos a cultivo."

El Archipiélago de Camagüey, en la costa norte de la zona centro-oriental de Cuba, se destaca por la presencia de elevados valores biológicos en paisajes bien conservados. Este trabajo explora la relación entre heterogeneidad de los paisajes físico-geográficos y la riqueza de flora vascular en ese territorio. La riqueza y diversidad del paisaje resultaron variables explicativas de la riqueza de especies de flora. El modelo estadístico que se obtuvo explica más del 82% de la relación. Los resultados sugieren que la riqueza de flora puede ser predicha por los valores de heterogeneidad geoecológica. En este sentido, se sugiere explorar la probable existencia de zonas de elevada biodiversidad en áreas de difícil acceso o poco conocidas, mediante análisis de heterogeneidad de paisajes físico-geográficos. The Camagüey Archipiélago, on the north coast of the central-eastern part of Cuba, stands out by elevated biological values in well preserved landscapes. This paper explores the relation between heterogeneity of the physical-geographical landscapes and vascular plant richness in that territory. Richness and landscape diversity turned out to be variables that explain the plant species richness. The statistical model obtained explains over 82% of the relation. The results suggest that the plant richness can be predicted by the geoecological heterogeneity values. In this sense, it is suggested to explore the probable existence of zones of elevated biodiversity in areas of difficult access or poorly known, through the analysis of physical-geographical landscape heterogeneity. O Arquipélago de Camagüey, na costa norte da zona centro-oriental de Cuba, se destaca pela presença de elevados valores biológicos nas paisagens bem conservadas. Este trabalho explora a relação entre heterogeneidade das paisagens físico-geográficas e a riqueza da flora vascular nesse território. A riqueza e diversidade da paisagem resultaram variáveis explicativas da riqueza de espécies da flora. O modelo estatístico que se obteve explica mais do 82% da relação. Os resultados sugerem que a riqueza da flora pode ser predita pelos valores de heterogeneidade geo-ecológica. Neste sentido, sugere-se explorar a provável existência de zonas de elevada biodiversidade em áreas de difícil acesso ou pouco conhecidas, mediante análise de heterogeneidade de paisagens físico-geográficos.

La heterogeneidad del paisaje varía en el espacio dependiendo de la proporción entre polígonos y unidades tipológicas. La alta variabilidad del espacio geográfico le confiere una elevada connotación ecológica, lo cual sugiere una estrecha relación con la distribución de la biodiversidad. El objetivo de este estudio es conocer si se puede predecir la riqueza de especies a través de indicadores de variabilidad espacial. Para esclarecer esto, se exploró la relación entre heterogeneidad del paisaje y la riqueza de flora, en tres cuencas costeras del estado de Veracruz. La riqueza, dominancia, abundancia y diversidad de los paisajes resultaron variables explicativas de la riqueza de especies. Los modelos obtenidos explican más de 75% de la relación. Estos resultados indican que la riqueza de especies de flora puede ser pronosticada por valores de heterogeneidad del paisaje. Se sugiere explorar la probable existencia de zonas de elevada biodiversidad en áreas de difícil acceso o poco conocidas, con el uso de sensores remotos.