Suchergebnisse

30 Págs., 7 Figs., 3 Tabls. Available online 15 September 2013. The definitive version is available at: http://link.springer.com/journal/12665 ; Soil moisture variability and the depth of water stored in the arable layer of the soil are important topics in agricultural research and rangeland management. In this study, we use the distributed rainfall-runoff (DR2) model to perform a detailed mapping of topsoil moisture status (SMS) in a mountain Mediterranean catchment. This model, previously tested in the same study area against the Palmer Z-index, is run at monthly scale for the current scenario of land uses and under three scenarios that combine the land abandonment and the application of the new common agricultural policy (CAP) of the European Union. Under the current conditions, runoff yield is scarce and presents a high spatial variability when monthly rainfall intensity and depth are low, and infiltration processes mainly lead to water storage in the soil. When rainfall intensity is high, runoff accumulation along the hillslopes controls the depth of available water in the soil, and SMS is more homogeneous. On average, scrublands and pasture have the wettest values, crops of winter cereal and abandoned fields have intermediate conditions, and areas of bare soil and forest have the driest conditions all the year around. The abandonment and no revegetation of the low productive fields located in steep areas and the collapse of their landscape linear elements (LLEs) produce not only an increase of 2.3 % of the overall SMS in the catchment in comparison with the current scenario but also an increment of the effective runoff that cross the cultivated areas of the lowlands and the runoff depth that reach the wetlands, increasing the soil erosion risk and compromising the conservation of the lakes. When the new green areas of the CAP are installed in the upper part of the fields of the lowlands and around the lakes, the runoff depth and thus siltation risk clearly decreases but also SMS decreases 1.7 and 1.1 % considering the current land uses and adding revegetation practices in the abandoned fields, respectively. Hence, a management scenario where: (1) abandoned fields are covered with a dense cover of shrubs, (2) the LLEs are preserved, (3) the green areas of the PAC are created, and (4) runoff harvesting practices are applied to partially compensate the water deficit, will help to preserve the humidity of the soil and will be of interest to keep the agricultural land use around the protected lakes of the study area. © 2013 Springer-Verlag Berlin Heidelberg. ; This research was funded by the Projects "Erosion and redistribution of soils and nutrients in Mediterranean agroecosystems: radioisotopic tracers of sources and sinks and modeling of scenarios (EROMED) (CGL2011-25486/BTE)" of the Spanish Ministry of Economy and Competitiveness (former Ministry of Science and Innovation) and "Mitigation of siltation of the Estaña Lakes Wetlands (Huesca, Spain) under different scenarios of climate change: soil and water trapping effectiveness of the "green areas" of the new CAP (Expedient number 2012 GA LC 034)" of the Regional Government of Aragón (Spain) and Obra Social "la Caixa" ; Peer reviewed

29 Pags., 3 Tabls., 6 Figs. The definitive version is available at: http://www.sciencedirect.com/science/journal/03783774 ; Hydrological and soil erosion models allow mapping and quantifying rates of runoff depths and soil redistribution for different land uses and climatic scenarios. Mediterranean soils are threatened by marked seasonal changes in the climatic, thus soil and vegetation parameters and modelling predictions at monthly scale are required. The semi-physically-based Soil Erosion and Redistribution Tool (SERT) model is presented together with the results of its application in a Mediterranean agro-ecosystem (NE Spain) with a detailed database. The hydrological module is based on the recently published DR2 (Distributed Rainfall-Runoff) water balance model and the effects of man-made infrastructures on the natural dynamics of runoff connectivity are added. The erosion module is built using, as the basis, the Revised Morgan, Morgan and Finney model, and the new Remaining runoff Transport Capacity (TCr) factor used to estimate the rates of soil loss and deposition. Predicted runoff depth varied in time and space, presenting areas without runoff production mainly in Rendzic Leptosols and Haplic Calcisols between November and April. Average soil erosion was high in cultivated and bare soils, ca. 20 and 10 Mg ha–1 yr–1, whereas rangeland soils were affected by moderate and, in some areas, by limited erosion processes. Soil erosion was minimal in February (0.08 Mg ha–1 month–1 on average) and 23 times higher in October. The SERT model allowed mapping the significant changes in the monthly values of soil redistribution quantifying the variability in the magnitude of the processes involved. Predicted values of average soil loss and deposition were validated against quantified values with 137Cs obtaining an average Nash–Sutcliffe efficiency of 0.48 (Pearson's r = 0.709) and a sediment balance of -1.15 Mg yr–1 for the whole catchment that is consistent with the karst processes of the study area. The new model is an easy-to-run, reliable, low-input-demanding management tool with valuable outputs for hydrological and soil erosion studies in small agricultural catchments. ; This research was funded by the Projects "Erosion and redistribution of soils and nutrients in Mediterranean agroecosystems: radioisotopic tracers of sources and sinks and modelling of scenarios (EROMED) (CGL2011-25486/BTE)" of the Spanish Ministry of Economy and Competitiveness (former Ministry of Science and Innovation) and "Mitigation of siltation of the Estaña Lakes Wetlands (Huesca, Spain) under different scenarios of climate change: soil and water trapping effectiveness of the "green areas" of the new CAP (Expedient number 2012 GA LC 034)" of the Regional Government of Aragón (Spain) and Obra Social "la Caixa". ; Peer reviewed

29 Pags.- 6 Tabls.- 6 Figs. This article belongs to a special issue of Catena titled "Geoecology in Mediterranean mountain areas. Tribute to Professor José María García Ruiz". The definitive version is available at: http://www.sciencedirect.com/science/journal/03418162 ; Understanding how organic carbon (OC) moves with sediments along the fluvial system is crucial to determining catchment scale carbon budgets and helps the proper management of fragile ecosystems. Especially challenging is the analysis of OC dynamics during fluvial transport in heterogeneous, fragile, and disturbed environments with ephemeral and intense hydrological pulses, typical of Mediterranean conditions. This paper explores the catchment scale OC redistribution by lateral flows in extreme Mediterranean environmental conditions, from a geomorphological perspective. The study area is a catchment (Cárcavo) in SE Spain with a semiarid climate, erodible lithologies, and shallow soils, which is highly disturbed by agricultural terraces, land levelling, reforestation, and construction of check-dams. To increase our understanding of catchment scale OC redistribution induced by erosion, we studied in detail the subcatchments of eight check-dams distributed along the catchments main channel. We determined 137Cs, physicochemical characteristics, and the OC pools of the catchment soils and sediments deposited behind each check-dam, performed spatial analysis of catchment properties and buffer areas around the check-dams, and carried out geomorphological analysis of the slope-channel connections. The soils showed very low total organic carbon (TOC) values, oscillating between 15.2 and 4.4 g kg− 1 for forest and agricultural soils, respectively. Sediments mobilized by erosion were poor in TOC (6.6 ± 0.7 g kg– 1) compared to the eroded (forest) soils, and the redistribution of OC through the catchment, especially of the mineral associated organic carbon (MAC) pool, showed the same pattern as clay particles and 137Cs. The TOC erosion rates estimated for the Cárcavo watershed are relatively low (0.031 ± 0.03 Mg ha− 1 y− 1) but similar to those reported for subhumid Mediterranean catchments that are less fragile and more conducive to plant growth. The TOC erosion/total erosion ratio was lower (0.06%) than other estimates, although the average OC concentration of the sediments was higher than that of the agricultural soils of the catchment, underlining the problem of maintaining sustainable soil OC contents. The OC in deposited sediments came not only from surface erosion processes, but also from deeper soil or sediment layers mobilized by concentrated erosion processes. Sediment richer in OC came from the surface soil of vegetated (reforested) areas close and well connected to the channels. Subcatchments dominated by laminar erosion processes showed a TOC erosion/total erosion ratio that was two times higher than that of subcatchments dominated by concentrated flow erosion processes. The lithology, soils, and geomorphology exert a more important control on OC redistribution than land use and vegetation cover in this geomorphologically very active catchment. ; This work was financially supported by the projects ADAPT (CGL2013-42009-R) and DISECO (CGL2014-55-405-R) from the Spanish Government, National Plan of Science; the project CAMBIO (18933/JLI/13) of the Seneca Foundation, Regional Government of Murcia (Spain); and the project SOGLO (P7/24 IAP BELSPO) from the Belgian Government. Joris de Vente was supported by a 'Ramón y Cajal' grant (RYC-2012-10375). ; Peer reviewed