Modelling the effect of land management changes on soil organic carbon stocks in a mediterranean cultivated field

28 Pags.- 5 Tabls.- 4 Figs. The definitive version is available at: http://onlinelibrary.wiley.com/journal/10.1002/(ISSN)1099-145XLand management in agricultural lands has important effects on soil organic carbon (SOC) dynamics. These effects are particularly relevant in the Mediterranean region, where soils are fragile and prone to erosion. Increasing interest of modelling to simulate SOC dynamics and the significance of soil erosion on SOC redistribution have been linked to the development of some recent models. In this study, the SPEROS-C model was implemented in a 1.6-ha cereal field for a 150-year period covering 100 years of minimum tillage by animal traction, 35 years of conventional tillage followed by 15 years of reduced tillage by chisel to evaluate the effects of changes in land management on SOC stocks and lateral carbon fluxes in a Mediterranean agroecosystem. The spatial patterns of measured and simulated SOC stocks were in good agreement, and their spatial variability appeared to be closely linked to soil redistribution. Changes in the magnitude of lateral SOC fluxes differed between land management showing that during the conventional tillage period the carbon losses is slightly higher (0.06 g C m−2 yr−1) compared to the period of reduced till using chisel (0.04 g C m−2 yr−1). Although the results showed that the SPEROS-C model is a potential tool to evaluate erosion induced carbon fluxes and assess the relative contribution of different land management on SOC stocks in Mediterranean agroecosystems, the model was not able to fully represent the observed SOC stocks. Further research (e.g. input parameters) and model development will be needed to achieve more accurate results.This work was funded by the CICYT project (CGL2014-52986-R).Peer reviewe

Movilización de carbono orgánico por distintos procesos erosivos en la conexión ladera-cauce

21 páginas, 5 figuras, 2 tablas.[ES] Con el fin de caracterizar la cantidad y tipo (lábil o recalcitrante) de carbono orgánico (CO) movilizado por distintos procesos erosivos identificados en las conexiones ladera-cauce, se estudiaron las características de los depósitos de erosión concentrada en cárcavas, erosión hídrica laminar, erosión lateral-gravitacional y erosión por laboreo en el contacto ladera-cauce de una cuenca de pequeño tamaño (10 ha) y se relacionaron con las características de los suelos-fuentes originales de donde procedían. La selectividad en el arranque y transporte de suelo de los distintos procesos se pudo asociar a diferentes contenidos y tipos de CO en los depósitos. Las razones de enriquecimiento de carbono orgánico sedimento/suelo fueron bajas (~0,40 ± 0,26), a pesar de haber un ligero enriquecimiento en partículas finas (correlacionadas positivamente con el CO) en los depósitos. Todo ello se atribuyó a los efectos de la mineralización en un cauce muy activo con pocas zonas de deposición y abundantes procesos de erosión no selectiva.[EN] With the purpose of analysing the type (labile or stable) and quantity of organic carbon (OC) mobilized by different erosive processes identified at the slope-bed connection, the erosion deposits of gullies, sheet erosion, bank erosion and tillage erosion were studied in a small catchment (10 ha) and compared to the characteristics of the catchment soils. Selectivity upon soil detachment and transport was associated to different OC content and types in the erosion deposits. Enrichment ratios of organic carbon sediment/soil were low (~0,40 ± 0,26), even though a slight enrichment was described for fine particles (positively correlated to CO). These results were attributed to mineralization processes prevailing over OC burial in a very active channel where depositional sites are scarce.Este trabajo ha sido financiado por los proyectos ERCO (CGL-2007- 62590/BTE) del Ministerio de Ciencia e Innovación y el proyecto PROBASE (CGL2006-11619). La primera autora tiene el apoyo económico de una ayuda FPI del Ministerio de Ciencia e Innovación (BES-2008-002379).Peer reviewe

Erosión del suelo y movilización de carbono orgánico a escala de cuenca: factores, procesos e impacto sobre el balance de carbono = Soil erosion and organic carbon mobilization at the catchment scale : factors, processes and impact on the carbon balance.

Los suelos son un componente importante del sumidero de carbono (C) terrestre que contribuye a la reducción de la concentración de carbono atmosférico. Varios estudios apuntan la importancia que la erosión del suelo puede tener sobre este sumidero, pero su efecto sigue siendo incierto. Esta tesis investiga el papel de los procesos de erosión del suelo en la redistribución de C orgánico del suelo en el paisaje y su impacto en el balance de C de una cuenca mediterránea. Mediante el uso de varias metodologías, se señaló la importancia de determinar las fuentes de sedimentos y procesos dominantes de erosión en el estudio de los flujos de redistribución así como sus implicaciones para la preservación del C movilizado. Durante el marco temporal estudiado (27 años), se estimó que la erosión hídrica redujo los stocks de C en los suelos. Sin embargo, como el ~80% C movilizado permaneció dentro de la cuenca, los procesos de erosión en el área de estudio contribuyeron a la creación de un sumidero neto de C. Palabras clave: Erosión hídrica del suelo, carbono orgánico del suelo, uso del suelo, fuentes de sedimentos, secuestro de carbono Abstract: Soils are an important component of the terrestrial carbon (C) sink that contributes to the reduction of atmospheric carbon. Several studies underline the capacity of soil erosion processes to enhance or diminish this terrestrial C sink, but their net effect remains unclear. This thesis investigates the role of soil erosion processes in the redistribution of soil organic C over the landscape and its impact on the C balance of a Mediterranean catchment. By using various methodologies, the importance of tracing sediment sources and dominant erosion processes when studying the redistribution of C by soil erosion was underlined, as well as their implications on the preservation of mobilized C. During the studied period (27 years), it was estimated that erosion-induced C fluxes reduced soil C stocks on the hillslopes. However, a net C sink was created since ~80% of the C mobilized by erosion remained inside the catchment. Keywords: Soil water erosion, soil organic carbon, land use, sediment sources, carbon sequestratio

Modelling the effect of agricultural management practices on soil organic carbon stocks: does soil erosion matter?

Over the last decades, an increasing number of studies have been conducted to assess the effect of soil management practices on soil organic carbon (SOC) stocks. At regional scales, biogeochemical models such as CENTURY or Roth-C have been commonly applied. These models simulate SOC dynamics at the profile level (point basis) over long temporal scales but do not consider the continuous lateral transfer of sediment that takes place along geomorphic toposequences. As a consequence, the impact of soil redistribution on carbon fluxes is very seldom taken into account when evaluating changes in SOC stocks due to agricultural management practices on the short and long-term. To address this gap, we assessed the role of soil erosion by water and tillage on SOC stocks under different agricultural management practices in the Walloon region of Belgium. The SPEROS-C model was run for a 100-year period combining three typical crop rotations (using winter wheat, winter barley, sugar beet and maize) with three tillage scenarios (conventional tillage, reduced tillage and reduced tillage in combination with additional crop residues). The results showed that including soil erosion by water in the simulations led to a general decrease in SOC stocks relative to a baseline scenario (where no erosion took place). The SOC lost from these arable soils was mainly exported to adjacent sites and to the river system by lateral fluxes, with magnitudes differing between crop rotations and in all cases lower under conservation tillage practices than under conventional tillage. Although tillage erosion plays an important role in carbon redistribution within fields, lateral fluxes induced by water erosion led to a higher spatial and in-depth heterogeneity of SOC stocks with potential effects on the soil water holding capacity and crop yields. This indicates that studies assessing the effect of agricultural management practices on SOC stocks and other soil properties over the landscape should account for the impact of soil erosion (both by water and tillage)

Exploring particle size distribution and organic carbon pools mobilized by different erosion processes at the catchment scale

Purpose: Selective water erosion of soil organic carbon (OC) has been reported to occur in small plots under field and laboratory conditions. However, little is known about how the process of OC erosion happens at larger scales. This study was conducted to assess the differences in the selectivity of OC between different erosion processes taking place within the same catchment. Materials and methods: A geomorphological survey of the hillslope-streambed connections within a catchment in SE Spain was conducted to determine and select the dominant erosion forms to be studied. Undisturbed sediment samples were taken from deposits derived from four different erosion processes (gully, interrill, bank and tillage erosion) and from the streambed sediment bars. Soils of the three main land uses (forest, shrubland and agricultural fields) of the drainage area were also sampled to establish comparisons with the sampled sediments and determine the enrichment ratios. Different organic carbon pools (size fractions) and particle size distribution, both dispersed and non-dispersed, were studied in soils and sediments. Results and discussion: All sediments were impoverished in OC compared to the source soils of the catchment. The largest differences were found between bank erosion and tillage erosion processes. Particle size distribution analysis indicated that soil particles were mainly being transported as aggregates. In addition, aggregates in the 250-63 μm size fraction seemed to contain primary silt and clay particles, which were positively correlated to total organic carbon. Bar sediments downstream in the streambed were impoverished in mineral-associated organic carbon, suggesting that this OC fraction can be carried further downstream by remaining in suspension longer due to its binding to smaller mineral particles. Conclusions: In general terms, there are indications that different erosion processes can result in different organic carbon enrichment ratios. Although selectivity during detachment, transport and deposition results in a complex set of interactions that need further research and field-based data, in this study, the nature of the erosion process, the characteristics of the source material and the level of aggregation of soil particles were found to be important variables. © 2011 Springer-Verlag

Calibration and application of an erosion and C redistribution model (SPEROS-C) to twelve small catchments in southeastern Spain

Results from various studies published during the last decades suggest that soil erosion could be playing an important role in the global carbon (C) cycle. One of the major uncertainties is related to the effect that lateral fluxes of sediment and C may have on soil C dynamics and on its distribution within the landscape. To approach its study from a modeling perspective, a model simulating redistribution processes of sediment and C, as well as the changes taking place within the soil profile when C is removed or deposited, is needed. However, not many models can currently perform these simulations, and the existing ones have been applied mainly to very homogeneous landscapes. Here we adapted, calibrated and validated a soil erosion and C redistribution model (SPEROS-C), successfully used in other regions, in order to estimate erosioninduced C fluxes in 12 small catchments (6-500 ha). These catchments were heterogeneous from a vegetation, lithology and topographical perspective. The estimated erosion and C redistribution rates were similar to those obtained in other studies. In the context of the C cycle, the balance between C loss, burial and replacement in eroded slopes in the catchment resulted, for most catchments, in a net C sequestration during the studied period (28 years). These results indicate that despite its multiple negative effects on ecosystems, soil erosion can induce C sequestration under specific conditions and temporal scales. © Universidad de La Rioja

Importance of land use patterns for erosion-induced carbon fluxes in a Mediterranean catchment

Land use and land cover (LULC) have a strong influence on the intensity of soil erosion processes and the consequent loss of soil organic carbon (C) and nutrients from soils. Yet, at the landscape scale most studies quantifying the effect of soil erosion on soil C dynamics have focused on homogeneous (mainly agricultural) areas. Here we study the effect of LULC patterns on erosion-induced lateral C fluxes and the net ecosystem C balance at the catchment level. The SPEROS-C model, a soil erosion model coupled with a C dynamics model, was applied to 12 catchments ranging from 8 to 430 ha in SE Spain and calibrated with field-based data on sediment yield and soil C concentration. Four LULC classes were considered: forest, shrubland, pasture and agriculture. Agricultural areas were the most dynamic sites accounting for 70% of the eroded soil but only for 45% of the total eroded C. The remaining percentage of eroded C derived mainly from relatively C rich forest soils which were the dominant LULC class in terms of spatial extent. The impact of soil erosion on annual ecosystem C fluxes was highest for agricultural soils due to lower C input and soil C stocks. During the study period (28 years), 26% of the eroded C remained within the catchments’ hillslopes deposited in 6% of the hillslope area, and not homogeneously distributed over the landscape. These results indicate that assessment of the role of soil erosion on soil C dynamics and ecosystem C fluxes should be undertaken from a landscape perspective, including the effects of LULC on the redistribution of erosion-induced C fluxes

The fame speech-to-speech translation system for catalan, english and spanish

Abstract. This paper describes the FAME interlingual speech-to-speech translation system for Spanish, Catalan and English, which is intended to assist users in the reservation of a hotel room when calling or visiting abroad. The system has been developed as an extension of the existing NESPOLE! translation system[4] which translates between English, German, Italian and French