Catena

Las regiones tropicales de montaña se ven afectados por el uso rápido de la tierra / cambio -cubrir, lo que puede poner en peligro sus (ecosistemas) funciones hidrológicas. Aunque existe un creciente interés en evaluar el efecto del uso del suelo / -Cubra cambiar sobre la hidrología de montaña, las evaluaciones cuantitativas del impacto del uso de la tierra / -cubrir sobre los procesos hidrológicos se ven obstaculizados por la falta de medidas de campo que caracterizan los procesos de generación de escorrentía. En este trabajo se presentan los resultados de los experimentos de campo de los mecanismos de escorrentía de lluvia en los Andes ecuatorianos sur. Un simulador de lluvia se utilizó para cuantificar la respuesta hidrológica de uso de la tierra distinta / -cubrir tipos de intensas lluvias (alrededor de 40 mm / h). Los experimentos de escorrentía de lluvia indican que las tierras degradadas y abandonadas generar escorrentía superficial dentro de unos pocos minutos después del inicio del evento de lluvia. Estas tierras tienen una respuesta hidrológica de laderas muy rápida y aguda, como el flujo hortoniano tierra es el mecanismo de generación de escorrentía dominante. En contraste, la escorrentía superficial en cultivo y pastizales es raro, ya que sus suelos se caracterizan por una alta capacidad de infiltración (es decir,> 29 mm / h). Nuestros experimentos demuestran que la generación de escorrentía en los ecosistemas andinos degradadas es controlado principalmente por la cobertura vegetal de la superficie y la gestión del suelo. Cuando la reducción de la cobertura vegetal de la superficie, el suelo está cada vez más afectado por el rápido escurrimiento ladera como la presencia de grandes cantidades de esmectitas en las rocas blandas afloramiento hace que el material muy propensos a la estanqueidad y la formación de costras, mejorando con ello la generación de escorrentía.Tropical mountain regions are affected by rapid land use/-cover change, which may threaten their (eco-) hydrological functions. Although there is a growing interest in evaluating the effect of land use/-cover change on mountain hydrology, quantitative assessments of the impact of land use/- cover on hydrological processes are hampered by the lack of field measurements characterizing runoff generation processes. In this paper, we present results from field experiments of rainfall runoff mechanisms in the southern Ecuadorian Andes. A rainfall simulator was used to quantify the hydrological response of distinct land use/-cover types to intense rainfall (about 40 mm/h). The rainfall runoff experiments indicate that degraded and abandoned land generate surface runoff within a few minutes after the start of the rainfall event. These lands have a very rapid and sharp hillslope hydrological response, as Hortonian overland flow is the dominant runoff generation mechanism. In contrast, surface runoff on arable and rangelands is rare, as their soils are characterized by a high infiltration capacity (i.e. N29 mm/h). Our experiments provide evidence that runoff generation in degraded Andean ecosystems is mainly controlled by the surface vegetation cover and land management. When reducing the surface vegetation cover, the soil is increasingly affected by rapid hillslope runoff as the presence of large amounts of smectites in the outcropping soft rocks makes the material very prone to sealing and crusting, thereby enhancing runoff generation.volumen 71; número

Geomorphology

Una gran variabilidad espacial en la producción de sedimentos se observó desde pequeños arroyos en los Andes ecuatorianos. El objetivo de este estudio fue analizar los factores ambientales que controlan estas variaciones en la producción de sedimentos en la cuenca del Paute, Ecuador. Datos de producción de sedimentos se calcularon sobre la base de los volúmenes de sedimentos acumulados detrás de presas de retención de 37 pequeñas cuencas. La media de producción de sedimentos específica anual (SSY) muestra una gran variabilidad espacial y oscila entre 26 y 15.100 kilometros Mg - 2 año - 1 . La media de la cubierta vegetal (C, fracción) en la cuenca, es decir, la cobertura vegetal en o cerca de la superficie, ejerce un primer control del orden en la producción de sedimentos. La cubierta vegetal fraccionada sola explica el 57% de la variación observada en ln (SSY). La relación exponencial negativa (SSY = una × e - b C ), que se encuentra entre la cubierta vegetal y la producción de sedimentos a escala de cuenca (10 3 -10 9 m 2 ), es muy similar a las ecuaciones derivadas de chapoteo, interregueros y surcos experimentos de erosión a escala de parcela (1-10 3 m 2 ). Esto afirma el carácter general de una disminución exponencial de la producción de sedimentos con el aumento de la cubierta vegetal en una amplia gama de escalas espaciales, siempre que la distribución de la cubierta puede ser considerada esencialmente aleatoria. Litología también afecta de manera significativa la producción de sedimentos, y explica un 23% adicional de la varianza observada en ln (SSY). Sobre la base de estos dos parámetros de captación, un modelo de regresión múltiple fue construido. Este modelo de regresión empírica ya explica más del 75% de la varianza total de la media anual de la producción de sedimentos. Estos resultados ponen de manifiesto el gran potencial de los programas de revegetación para el control de la producción de sedimentos. Demuestran que un ligero aumento en la cobertura vegetal fraccionada general de las tierras degradadas es probable que tenga un gran efecto en la producción y entrega de sedimentos. Por otra parte, señalan la importancia de los datos detallados de la vegetación de superficie para predecir y modelar las tasas de producción de sedimentos.A large spatial variability in sediment yield was observed from small streams in the Ecuadorian Andes. The objective of this study was to analyze the environmental factors controlling these variations in sediment yield in the Paute basin, Ecuador. Sediment yield data were calculated based on sediment volumes accumulated behind checkdams for 37 small catchments. Mean annual specific sediment yield (SSY) shows a large spatial variability and ranges between 26 and 15,100 Mg km−2 year−1 . Mean vegetation cover (C, fraction) in the catchment, i.e. the plant cover at or near the surface, exerts a first order control on sediment yield. The fractional vegetation cover alone explains 57% of the observed variance in ln(SSY). The negative exponential relation (SSY =a×e −b C) which was found between vegetation cover and sediment yield at the catchment scale (103 –109 m2 ), is very similar to the equations derived from splash, interrill and rill erosion experiments at the plot scale (1–103 m2 ). This affirms the general character of an exponential decrease of sediment yield with increasing vegetation cover at a wide range of spatial scales, provided the distribution of cover can be considered to be essentially random. Lithology also significantly affects the sediment yield, and explains an additional 23% of the observed variance in ln(SSY). Based on these two catchment parameters, a multiple regression model was built. This empirical regression model already explains more than 75% of the total variance in the mean annual sediment yield. These results highlight the large potential of revegetation programs for controlling sediment yield. They show that a slight increase in the overall fractional vegetation cover of degraded land is likely to have a large effect on sediment production and delivery. Moreover, they point to the importance of detailed surface vegetation data for predicting and modeling sediment production rates.volumen 98; temas 3-

Vegetation and topographic controls on sediment deposition and storage on gully beds in a degraded mountain area

Active gully systems developed on highly weathered or loose parent material are an important source of runoff and sediment production in degraded areas. However, a decrease of land pressure may lead to a return of a partial vegetation cover, whereby gully beds are preferred recolonization spots. Although the Current knowledge on the role of vegetation on reducing sediment production on slopes is well developed, few Studies exist on the significance of restoring sediment transport pathways on the total sediment budget of degraded mountainous catchments. This study in the Ecuadorian Andes evaluates the potential of vegetation to stabilize active gully systems by trapping and retaining eroded sediment in the gully bed, and analyses the significance of vegetation restoration in the gully bed in reducing sediment export from degraded catchments. Field measurements on 138 gully segments located in 13 ephemeral steep gullies with different ground vegetation cover indicate that gully bed vegetation is the most important factor in promoting short-term (1-15 years) sediment deposition and gully stabilization. In well-vegetated gully systems (>= 30% of ground vegetation cover), 0.035 m(3) m(-1) of sediment is deposited yearly in the gully bed. Almost 50 per cent of the observed variance in sediment deposition volumes can be explained by the mean ground vegetation cover of the gully bed. The presence of vegetation in gully beds gives rise to the formation of vegetated buffer zones, which enhance short-term sediment trapping even in active gully systems in mountainous environments. Vegetation buffer zones are shown to modify the connectivity of sediment fluxes, as they reduce the transport efficiency of gully systems. First calculations on data on sediment deposition patterns in our study area show that gully bed deposition in response to gully bed revegetation can represent more than 25 per cent of the volume of sediment generated within the catchment. Our findings indicate that relatively small changes in landscape connectivity have the potential to create strong (positive) feedback loops between erosion and vegetation dynamics. Copyright (C) 2009 John Wiley & Sons, Ltd

Check dams and afforestation reducing sediment mobilization in active gully systems in the Andean mountains

Gully erosion is an important process of land degradation in mountainous regions, and is known to be one of the major sediment sources in eroded catchments. Recent studies have suggested that living and dead vegetation can be effective for ecosystem restoration, and large-scale restoration projects have been implemented in the tropical Andes in recent decades. However, few quantitative studies exist on the effectiveness of gully restoration to reduce sediment production and mobilization. In this study, sediment mobilization and transport was studied in five micro-catchments (70%) of the amount of sediment exported from the micro-catchments. The construction of wooden barriers (or so-called check dams) in active gully channels enhances sediment deposition in the gully bed. The latter is strongly dependent on the rainfall intensity, as well as gully channel slope and vegetation cover. The experimental data suggest that there exists a threshold value of rainfall intensity (I30max) of about 23mmh−1, above which all sections of the gully system are actively contributing water and sediment to the river network. Also, forestation of active gully systems with rapidly growing exotic species such as Eucalyptus has a positive effect on the stabilization and restoration of the badlands, and effectively reduces the sediment export

Check dams and afforestation reducing sediment mobilization in active gully systems in the Andean mountains

© 2018 Elsevier B.V. Gully erosion is an important process of land degradation in mountainous regions, and is known to be one of the major sediment sources in eroded catchments. Recent studies have suggested that living and dead vegetation can be effective for ecosystem restoration, and large-scale restoration projects have been implemented in the tropical Andes in recent decades. However, few quantitative studies exist on the effectiveness of gully restoration to reduce sediment production and mobilization. In this study, sediment mobilization and transport was studied in five micro-catchments (70%) of the amount of sediment exported from the micro-catchments. The construction of wooden barriers (or so-called check dams) in active gully channels enhances sediment deposition in the gully bed. The latter is strongly dependent on the rainfall intensity, as well as gully channel slope and vegetation cover. The experimental data suggest that there exists a threshold value of rainfall intensity (I30max) of about 23 mm h−1, above which all sections of the gully system are actively contributing water and sediment to the river network. Also, forestation of active gully systems with rapidly growing exotic species such as Eucalyptus has a positive effect on the stabilization and restoration of the badlands, and effectively reduces the sediment export.status: publishe

Be2D: A model to understand the distribution of meteoric 10Be in soilscapes

status: publishe

Earth Surface Processes and Landforms

Sistemas de cárcavas activas desarrolladas en material parental altamente degradado o sueltos son una fuente importante de escorrentía y sedimentos de producción en las zonas degradadas. Sin embargo, una disminución de la presión sobre la tierra puede conducir a un retorno de una cubierta vegetal parcial, mediante el cual camas barranco se prefieren los puntos de recolonización. Aunque los conocimientos actuales sobre el papel de la vegetación en la reducción de la producción de sedimentos en las pendientes está bien desarrollada, existen pocos estudios sobre la importancia de la restauración de las vías de transporte de sedimentos en el presupuesto total de los sedimentos de las cuencas montañosas degradadas. Este estudio en los Andes ecuatorianos evalúa el potencial de la vegetación para estabilizar los sistemas de cárcavas activas al atrapar y retener el sedimento erosionado en la cama barranco, y analiza la importancia de la restauración de la vegetación en el lecho del barranco en la reducción de la exportación de sedimentos de cuencas degradadas. Las mediciones de campo en 138 segmentos cárcavas ubicadas en 13 barrancos escarpados efímeros con diferente cobertura vegetal del suelo indican que la vegetación cama barranco es el factor más importante en la promoción a corto plazo (1-15 años) deposición de sedimentos y estabilización de cárcavas. En los sistemas de cárcavas y vegetación-(≥ 30% de la cubierta vegetal del suelo), 0.035 m 3 m -1 de sedimento se deposita anualmente en la cama barranco. Casi el 50 por ciento de la variación observada en los volúmenes de deposición de sedimentos puede ser explicado por la cubierta media vegetación del suelo de la cama barranco. La presencia de vegetación en camas barranco da lugar a la formación de zonas de amortiguamiento con vegetación, que mejoran la retención de sedimentos a corto plazo, incluso en los sistemas de cárcavas activas en ambientes montañosos. Zonas de amortiguamiento de la vegetación se muestran para modificar la conectividad de los flujos de sedimentos, ya que reducen la eficiencia del transporte de los sistemas de cárcavas. Los primeros cálculos en datos sobre los patrones de deposición de sedimentos en nuestra área de estudio muestran que Gully deposición cama en respuesta a Gully cama revegetación pueden representar más del 25 por ciento del volumen de sedimento generado dentro de la cuenca. Nuestros resultados indican que cambios relativamente pequeños en la conectividad del paisaje tienen el potencial de crear una fuerte retroalimentación (positivo) bucles entre la dinámica de la erosión y de la vegetación. Copyright © 2009 John Wiley & Sons, Ltd.Active gully systems developed on highly weathered or loose parent material are an important source of runoff and sediment production in degraded areas. However, a decrease of land pressure may lead to a return of a partial vegetation cover, whereby gully beds are preferred recolonization spots. Although the current knowledge on the role of vegetation on reducing sediment production on slopes is well developed, few studies exist on the significance of restoring sediment transport pathways on the total sediment budget of degraded mountainous catchments. This study in the Ecuadorian Andes evaluates the potential of vegetation to stabilize active gully systems by trapping and retaining eroded sediment in the gully bed, and analyses the significance of vegetation restoration in the gully bed in reducing sediment export from degraded catchments. Field measurements on 138 gully segments located in 13 ephemeral steep gullies with different ground vegetation cover indicate that gully bed vegetation is the most important factor in promoting short-term (1–15 years) sediment deposition and gully stabilization. In well-vegetated gully systems ( ≥ 30% of ground vegetation cover), 0.035 m3 m–1 of sediment is deposited yearly in the gully bed. Almost 50 per cent of the observed variance in sediment deposition volumes can be explained by the mean ground vegetation cover of the gully bed. The presence of vegetation in gully beds gives rise to the formation of vegetated buffer zones, which enhance short-term sediment trapping even in active gully systems in mountainous environments. Vegetation buffer zones are shown to modify the connectivity of sediment fluxes, as they reduce the transport efficiency of gully systems. First calculations on data on sediment deposition patterns in our study area show that gully bed deposition in response to gully bed revegetation can represent more than 25 per cent of the volume of sediment generated within the catchment. Our findings indicate that relatively small changes in landscape connectivity have the potential to create strong (positive) feedback loops between erosion and vegetation dynamics. Copyright © 2009 John Wiley & Sons, Ltd.volumen 34; número

Integrating river incision rates over timescales in the Ecuadorian Andes: from uplift history to current erosion rates

status: publishe