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Sediment transport is the main driver of the channel morphology and landscape evolution, with implications for chemical and biological river processes, and human-related activities. Understanding the processes governing the relations between discharge and suspended sediments is essential for the management of river catchments and river networks. Here, we use the method of wavelet transformation to identify the time-scale dependency of suspended sediment patterns concerning the temporally and spatially uneven transient processes of sediment production, accumulation, and transport. We analyze the temporal variation of concurrent discharge and suspended sediment fluxes for the Upper Changjiang (Yangtze River, China) at Pingshan station by using a long-term database collected for over 50 years. Furthermore, we bridge the limitations of pure predictive models to learn from temporal data structures with the main purpose of identifying the mechanisms underpinning the suspended sediment patterns (e.g., climatic forces). Intraseasonal-to-seasonal, annual, and inter-annual dominant time-scales are thus identified. The short time-scales are driven by the bi-modal seasonal precipitation pattern specific to the climate of the region and provide a continuous supply of sediments to the river. The large time-scales, controlled by high magnitude flow events and within-reach sediment storage, display alternating periods of increasing and decreasing sediment fluxes; ultimately, they maintain the river channel within balance or within a moderate positive sediment accumulation process. This analysis and methodology help to understand temporal sediment dynamics, and ultimately to manage river catchments. ; This work was funded by the H2020-MSCA-IF-2018 programme (Marie Sklodowska-Curie Actions) of the European Union under REA grant agreement, number SEDILAND-834329. ; Peer reviewed

Human-induced afforestation has been one of the main policies for environmental management of farmland abandonment in Mediterranean areas. Over the last decades, several studies have reviewed the impact of afforestation activities on geomorphological and hydrological responses and soil properties, although few studies have evaluated the effects on water table dynamics. In parallel to human-induced afforestation activities, natural revegetation occurred in abandoned fields and in fields where the intensity of human activity declined, driving the expansion of shrubs. This research addresses the spatial and temporal variability of water table dynamics in a small afforested sub-catchment located in the Central Spanish Pyrenees. Differences between afforestation (Pinus nigra and Pinus sylvestris) and natural plant colonization (shrubs, mainly Genista scorpius, Buxus sempervirens, and Juniperus communis) and early abandoned meadows (G. scorpius), are analysed in terms of runoff generation and seasonal water table depth dynamics. Precipitation, runoff and water table datasets recorded for the 2014–2019 period are used. Results show a high temporal and spatial variability with large fluctuations in discharge and water table. Groundwater dynamics varied markedly over the year, identifying a wet and dry period with different responses suggesting different runoff generation processes (Hortonian flow during dry and wet periods, and saturation excess runoff during wet conditions). Furthermore, important differences are noted among the various land cover types: (i) in the natural revegetation area (shrubland and meadows) a marked seasonal cycle was observed with short saturation periods during winter and spring; and (ii) in the afforestation areas, the water table dynamics showed a seasonal cycle with a high variability, with fast responses and rapid oscillations. Likewise, the relationship between the depth of water table and hydrological variables was not straightforward, suggesting complex hydrological behaviour. ; This work was funded by the H2020-MSCA-IF-2018 programme (Marie Sklodowska-Curie Actions) of the European Union under REA grant agreement, number 834329-SEDILAND, and by the MANMOUNT project (PID2019-105983RB-I00/AEI/10.13039/501100011033, funded by MICINN-FEDER). ; Peer reviewed

16 Pags. This article as a Preface by the Editors belonging 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 ; The origin of this special issue arose from a scientific meeting held in Logroño (Spain) in October 2014, under the theme Geoecology in extreme environments: mountains and semiarid areas ( Arnáez et al., 2014). The main motivation of the event was to recognise, on the occasion of his retirement, the outstanding contribution of Prof. José María García-Ruiz to the progress of Geoecology in Mediterranean mountain areas. Prof. García-Ruiz (Zaragoza, 1949) was lecturer, between 1974 and 1987, at the University of Cáceres and La Rioja. As staff Scientist and later Professor at the Spanish National Research Council (CSIC), he was Head of the Pyrenean Institute of Ecology (IPE-CSIC) (1987–1990) and Head of the Department of Global Change at the same institute, President of the Spanish Society of Geomorphology (1994–1996), besides a productive and tireless researcher. He has published more than 300 scientific articles, one third of them in international journals, and more than 35 books. He has participated in 40 research projects funded by the European Commission, Spanish and regional governments. With his enthusiasm and dedication he has inspired and encouraged a wide number of geographers and geomorphologists, including 10 PhD students and a great number of collaborators, most of them now working at different Universities and Research Centres around the world. ; Peer reviewed

The definitive version is available at: http://www.sciencedirect.com/science/article/pii/S0169555X13003073# ; [EN] Intense erosion processes are widespread in the Mediterranean region, and include sheet wash erosion, rilling, gullying, shallow landsliding, and the development of large and active badlands in both subhumid and semi-arid areas. This review analyses the main environmental and human features related to soil erosion processes, and the main factors that explain the extreme variability of factors influencing soil erosion, particularly recent land use changes. The importance of erosion in the Mediterranean is related to the long history of human activity in a region characterized by low levels of annual precipitation, the occurrence of intense rainstorms and long-lasting droughts, high evapotranspiration, the presence of steep slopes and the occurrence of recent tectonic activity, together with the recurrent use of fire, overgrazing and farming. These factors have resulted in a complex landscape in which intensification and abandonment, wealth and poverty can co-exist. The changing conditions of national and international markets and the evolution of population pressure are now the main drivers explaining land use changes, including farmland abandonment in mountain areas, the expansion of some subsidized crops to marginal lands, and the development of new terraces affected by landslides and intense soil erosion during extreme rainstorm events. The occurrence of human-related forest fires affecting thousands of hectares each year is a significant problem in both the northern and southern areas of the Mediterranean basin. Here, we highlight the rise of new scientific challenges in controlling the negative consequences of soil erosion in the Mediterranean region: 1) to reduce the effects and extent of forest fires, and restructure the spatial organization of abandoned landscapes; 2) to provide guidance for making the EU agricultural policy more adapted to the complexity and fragility of Mediterranean environments; 3) to develop field methods and models to improve the identification of runoff and sediment contributing areas; 4) to contribute to the conservation of landscapes (i.e. bench-terraced fields) having high cultural and productivity values; 5) to improve knowledge of the hydrological and geomorphological functioning of badlands, with the aim of reducing sediment yield and accessibility; 6) to better understand the effect of climate change on soil erosion in the Mediterranean region; and 7) to improve quantitative information on long-term soil erosion. ; Support for this research was provided by the projects INDICA (CGL2011- 27753-C02-01 and -02), HIDROCAES (CGL2011-27574-C02-01) and DISDROSPEC (CGL2011-24815), funded by the Spanish Ministry of Economy and Competitiveness and the European Regional Development Fund (ERDF-FEDER), ACQWA (FP7-ENV- 2007-1-212250), financed by the European Commission, and an agreement between the CSIC and the Spanish Ministry of Environment (RESEL). The Geomorphology and Global Change research group was financed by the Aragón Government and the European Social Fund (ESF-FSE). E. Nadal-Romero and N. Lana-Renault benefited from a research contract (Spanish Ministry of Economy and Competitiveness, Programme Juan de la Cierva). The authors acknowledge the comments from Prof. Mike Fullen and an anonymous referee, as well as the editorial labour from Prof. Takashi Oguchi. ; Peer reviewed

51 Pags.- 9 Figs. The definitive version is available at: http://onlinelibrary.wiley.com/journal/10.1002/(ISSN)1099-145X ; Soil erosion is a threat to food security, especially in regions where the area of arable land is shrinking dramatically because of soil degradation. Research on soil erosion expanded progressively throughout the 20th centu\ry, although a number of unresolved problems persist despite this issue being crucial for the environment and the welfare of society. Some basic unresolved issues, including the absence of a universally accepted definition of soil erosion and disagreement about how to measure it have contributed to a degree of scientific stagnation. Accurate prediction of the response of soils to disturbance is hampered by the dependence of the erosion process on the spatial scale involved, the time lag between the disturbance and the erosion response and the short periods for which data are typically available. We argue that devoting increased attention to the following environmental, demographic, political and societal issues will reinvigorate progress in the field. (i) The relationships between on-site and off-site consequences of soil erosion need to be elucidated if the economic and environmental costs are to be adequately assessed. (ii) Effective measures for soil conservation need to focus on spatial patterns of plant cover that reduce sediment connectivity, and most importantly on the relationships between hillslopes and sediment transfer in eroded channels. (iii) The scientific community must be able to identify early warning signs of critical transitions, if irreversible soil degradation is to be prevented. (iv) Consensus needs to be reached concerning the contribution of soil erosion to the carbon cycle. (v) The consequences of climate change on erosion and sediment transport should be investigated in depth. (vi) The general society needs to perceive soil erosion as a critical matter requiring an urgent response. ; This research was supported by the projects ESPAS (CGL2015-65569-R) and INDICA (CGL2011-27753-C02-01 and 02) (MINECO/FEDER). The research groups on "Geomorphology and Global Change" and "Climate, Water, Global Change and Natural Systems" were financed by the Aragón Government and the European Social Fund (ESF). E. Nadal-Romero was the recipient of a "Ramón y Cajal" postdoctoral contract (Spanish Ministry of Economy and Competitiveness). The research leading to these results has received funding from the European Union Seventh Framework Programme (FP7/2007–2013) under grant agreement no 603498 (RECARE project). ; Peer reviewed

Rainfall is the key factor to understand soil erosion processes, mechanisms, and rates. Most research was conducted to determine rainfall characteristics and their relationship with soil erosion (erosivity) but there is little information about how atmospheric patterns control soil losses, and this is important to enable sustainable environmental planning and risk prevention. We investigated the temporal and spatial variability of the relationships of rainfall, runoff, and sediment yield with atmospheric patterns (weather types, WTs) in the western Mediterranean basin. For this purpose, we analyzed a large database of rainfall events collected between 1985 and 2015 in 46 experimental plots and catchments with the aim to: (i) evaluate seasonal differences in the contribution of rainfall, runoff, and sediment yield produced by the WTs; and (ii) to analyze the seasonal efficiency of the different WTs (relation frequency and magnitude) related to rainfall, runoff, and sediment yield. The results indicate two different temporal patterns: the first weather type exhibits (during the cold period: autumn and winter) westerly flows that produce the highest rainfall, runoff, and sediment yield values throughout the territory; the second weather type exhibits easterly flows that predominate during the warm period (spring and summer) and it is located on the Mediterranean coast of the Iberian Peninsula. However, the cyclonic situations present high frequency throughout the whole year with a large influence extended around the western Mediterranean basin. Contrary, the anticyclonic situations, despite of its high frequency, do not contribute significantly to the total rainfall, runoff, and sediment (showing the lowest efficiency) because of atmospheric stability that currently characterize this atmospheric pattern. Our approach helps to better understand the relationship of WTs on the seasonal and spatial variability of rainfall, runoff and sediment yield with a regional scale based on the large dataset and number of soil erosion experimental stations. ; Spanish Government (Ministry of Economy and Competitiveness, MINECO) and FEDER Projects: CGL2014 52135-C3-3-R, ESP2017-89463-C3-3-R, CGL2014-59946-R, CGL2015-65569-R, CGL2015-64284-C2-2-R, CGL2015-64284-C2-1-R, CGL2016-78075-P, GL2008-02879/BTE, LEDDRA 243857, RECARE-FP7, CGL2017-83866-C3-1-R, and PCIN-2017-061/AEI. Dhais Peña-Angulo received a 'Juan de la Cierva' postdoctoral contract (FJCI-2017-33652 Spanish Ministry of Economy and Competitiveness, MEC). Ana Lucia acknowledge the 'Brigitte-Schlieben-Lange-Programm'. The 'Geoenvironmental Processes and Global Change' (E02_17R) was financed by the Aragón Government and the European Social Fund. José Andrés López-Tarazón acknowledges the Secretariat for Universities and Research of the Department of the Economy and Knowledge of the Autonomous Government of Catalonia for supporting the Consolidated Research Group 2014 SGR 645 (RIUS-Fluvial Dynamics Research Group). Artemi Cerdá thank the funding of the OCDE TAD/CRP JA00088807. José Martínez-Fernández acknowledges the project Unidad de Excelencia CLU-2018-04 co-funded by FEDER and Castilla y León Government. Ane Zabaleta is supported by the Hydro-Environmental Processes consolidated research group (IT1029-16, Basque Government). This paper has the benefit of the Lab and Field Data Pool created within the framework of the COST action CONNECTEUR (ES1306). This research was supported by projects funded by Spanish and FEDER, the 'Brigitte-Schlieben-Lange-Programm'; the Governments of Spanish Autonomous Region of Aragón, Catalonia, Castilla-León and Basque Country. José Andrés López-Tarazón acknowledges the Secretariat for Universities and Research of the Department of the Economy and Knowledge of the Autonomous Government of Catalonia for supporting the Consolidated Research Group 2014 SGR 645 (RIUS-Fluvial Dynamics Research Group). Artemi Cerdá thank the funding of the OCDE TAD/CRP JA00088807. José Martínez-Fernández acknowledges the project Unidad de Excelencia CLU-2018-04 co-funded by FEDER and Castilla y León Government. Ane Zabaleta is supported by the Hydro-Environmental Processes consolidated research group (IT1029-16, Basque Government). This paper has the benefit of the Lab and Field Data Pool created within the framework of the COST action CONNECTEUR (ES1306).

Badlands are landforms that occur all over the World. In the Mediterranean region, badlands are found in both dry (arid and semi‐arid) and wet (subhumid and humid) environments, and are characterized by complex hydro‐geomorphological dynamics, high intense erosion processes and extreme sediment yield. Understanding the impact of Global Change is key to predict the on‐site and off‐site effects on badland dynamics, particularly its consequences on bedrock weathering, on sediment yield and delivery and on plant colonization. Here, conducting a systematic literature review, we analyzed an extensive database and identified the main climate‐drivers affecting the hydro‐geomorphological dynamics in Mediterranean badlands (based on non‐metric multidimensional scaling and structural equation modeling analysis). Later, we examined the main impacts expected from climate change forecasting in the near future, and we explored the interactions between badlands response to climate variation. In Mediterranean badlands, weathering processes are mainly related to wetting–drying cycles and freeze–thaw cycles in dry and wet badlands, respectively. In both environments, rainfall amount appears as the main driver for runoff response, and rainfall amount and rainfall intensity for erosion dynamics. Future climate scenarios forecast a decrease in annual rainfall, number of rainfall events and frost days, and in soil moisture, and an increase in rainfall intensity. These changes will have direct hydro‐geomorphological implications with direct and indirect effects on badland dynamics. This may result in a decrease in annual runoff in dry badlands, but the occurrence of more frequent extreme events would increase soil erosion and could negatively affect biological soil crust. In wet badlands, weathering and erosion processes may decrease, and a stabilization of the slopes, with consequently improved vegetation growth, may be expected. In addition, the forecasted changes must be taken into account, especially considering the possible off‐site effects of these extreme environments. ; This work was funded by the H2020‐MSCA‐IF‐2018 program (Marie Sklodowska‐Curie Actions) of the European Union under REA grant agreement, number 834329‐SEDILAND, the REBIOARID (RTI2018‐101921‐B‐I00) and MANMOUNT (PID2019‐105983RB‐100/AEI/10.13039/501100011033) projects funded by the Spanish National Plan for Research (Ministerio de Ciencia e Innovación) and the European Union ERDF funds and the RH2O‐ARID project (P18‐RT‐5130) funded by Consejería de Economía, Innovación, Ciencia y Empleo, Junta de Andalucía and the European Union ERDF funds. ERC and SC are supported by a HIPATIA‐UAL postdoctoral fellowship funded by the University of Almeria. ; Peer reviewed

49 páginas, 13 figuras ; Over the last century extraordinary efforts have been devoted to determining soil erosion rates (in units of mass per area and time) under a large range of climatic conditions and land uses, and involving various measurement methods. We undertook a meta-analysis of published data from more than 4000 sites worldwide. The results show that there is extraordinarily high variability in erosion rates, with almost any rate apparently possible irrespective of slope, climate, scale, land use/land cover and other environmental characteristics. However, detailed analysis revealed a number of general features including positive relationships of erosion rate with slope and annual precipitation, and a significant effect of land use, with agricultural lands yielding the highest erosion rates, and forest and shrublands yielding the lowest. Despite these general trends, there is much variability that is not explained by this combination of factors, but is related, at least partially, to the experimental conditions. Our analysis revealed a negative relationship between erosion rate and the size of the study area involved; significant differences associated with differing measurement methods, with direct sediment measurement yielding the lowest erosion rates, and bathymetric, radioisotope and modeling methods yielding the highest rates; and a very important effect of the duration of the experiment. Our results highlight that, when interpreting erosion rates, the experimental conditions involved must be taken into account. Even so, the data suggest that only order of magnitude approximations of erosion rates are possible, and these retain a very large degree of uncertainty. Consequently, for practical purposes such as calculation of global sediment budgets, empirical equations are not a substitute for direct measurements. Our results also show that a large proportion of the experiments have been short-term (less than 3. years), which reduces dramatically the reliability of the estimated erosion rates, given the highly non-normal behavior of soil erosion (time-dependency). Despite the efforts already made, more long-term measurement experiments need to be performed, especially in regions of the world that are under-represented in global datasets. In addition, protocols need to be established for standardizing the measurement methods and reporting the results, to enable data to be compared among diverse sites. ; Support for this research was provided by the projects INDICA (CGL2011-27753-C02-01 and -02) and HIDROCAES (CGL2011-27574-C02-C01), funded by the Spanish Ministry of Economy and Competitiveness, and an agreement between the CSIC and the Spanish Ministry of Environment (RESEL). The Geomorphology and Global Change research group was financed by the Aragón Government and the European Social Fund (ESF-FSE) (E68). Estela Nadal-Romero and Yasmina Sanjuán were the recipients of a "Marie Curie-IEF" postdoctoral contract (Project 624974) and an FPI pre-doctoral contract from the European Commission and the Spanish Ministry of Economy and Competitiveness, respectively. ; Peer reviewed

Four experimental catchments in the Central Pyrenees were monitored by the Department of Geo-environmental Processes and Global Change (Pyrenean Institute of Ecology, CSIC) to assess the hydrological and geomorphological consequences of various land uses and vegetation cover. The catchments were selected along an altitudinal and land-use gradient and included: (i) a sub-Mediterranean environment affected by intense weathering and erosion processes on marls, (ii) an old abandoned cultivated area undergoing vegetation regrowth, (iii) a barely-disturbed forest area, and (iv) a sub-alpine grassland in the high mountains, affected by snow accumulation and melting processes. The results demonstrate that plant cover is a key factor influencing the suspended sediment concentration, total sediment yield and proportion of different types of sediment. ; Support for this research was provided by the following projects: PROBASE (CGL2006- 11619/HID CONSOLIDER), CETSUS (CGL2007-66644-C04-01/HID) and RESEL financed by the Spanish Government, and PI032/08 financed by the Aragón Government. E. Nadal has benefited from a research contract (I-D+I 2008-2011 National Program), funded by the Spanish Ministry of Education and Science. ; Peer Reviewed

The hydrological and geomorphological effects of an exceptional rainstorm event that occurred in the central Spanish Pyrenees during 19-21 October 2012 were studied in five experimental catchments under various land covers: (i) subhumid badlands; (ii) dense forest; (iii) an abandoned farmland area recolonized by shrubs and forest patches; and (iv) subalpine grasslands. Hydrographs and sedigraphs demonstrated that vegetation cover is a major factor affecting the control of floods even during exceptional rainstorms, at least at the spatial scale at which the phenomenon was studied (catchment sizes: 0.3-2.8 km2) and under dry catchment conditions. The combined precipitation over the two days (c. 250 mm) was the greatest for any two-day event recorded since 1950 in the central-western Pyrenees for all but one of the stations in the study. Five pulses of most intense rainfall were recorded. The forested catchment did not react to the two most intense rainfall pulses, because of the very low antecedent level of the water table. The main peak flow occurred only when at least a part of the catchment was saturated. The abandoned farmland catchment had two small peak discharges at the beginning of the event, which were produced by infiltration excess overland flow from eroded areas close to the main stream. During the third most intense rainfall period a large part of this catchment contributed to runoff and a relatively high peak discharge was produced. The badland catchment reacted immediately from the beginning of the rainstorm, yielding very high discharges accompanied by high suspended sediment concentrations. The subalpine catchment showed a hydrograph mirroring the hyetograph, with brief but intense hydrological responses to increased precipitation, because of the marked gradients and the presence of bare rock in the headwaters. A high volume of bedload was carried during the peak discharge. © 2013 John Wiley & Sons, Ltd. ; Support for this research was provided by the projects INDICA (CGL2011-27753-C02-01 and −02) and HIDROCAES (CGL2011-27574-C02-01), funded by the Spanish Ministry of Economy and Innovation; ACQWA (FP7-ENV-2007-1-212250), financed by the European Commission; and an agreement between the CSIC and the Spanish Ministry of Environment (RESEL). The research group on Geomorphology and Global Change was financed by the Aragón Government and the European Social Fund (ESF-FSE). N. Lana-Renault and E. Nadal-Romero were recipients of a research contract (Spanish Ministry of Economy and Competitiveness, Programme Juan de la Cierva). ; Peer Reviewed

4 páginas, 2 figuras, 1 tabla.-- Comunicación presentada al Congreso Internacional sobre Desertificación (Tpic 2: Soil erosion and desertification) celebrado del 16 al 18 de Septiembre del 2009. ; Four experimental catchments in the Central Pyrenees were monitored by the Department of Geo-environmental Processes and Global Change (Pyrenean Institute of Ecology, CSIC) to assess the hydrological and geomorphological consequences of various land uses and vegetation cover. The catchments were selected along an altitudinal and land-use gradient and included: (i) a sub-Mediterranean environment affected by intense weathering and erosion processes on marls, (ii) an old abandoned cultivated area undergoing vegetation regrowth, (iii) a barely-disturbed forest area, and (iv) a sub-alpine grassland in the high mountains, affected by snow accumulation and melting processes. The results demonstrate that plant cover is a key factor influencing the suspended sediment concentration, total sediment yield and proportion of different types of sediment. ; Support for this research was provided by the following projects: PROBASE (CGL2006- 11619/HID CONSOLIDER), CETSUS (CGL2007-66644-C04-01/HID) and RESEL financed by the Spanish Government, and PI032/08 financed by the Aragón Government. E. Nadal has benefited from a research contract (I-D+I 2008-2011 National Program), funded by the Spanish Ministry of Education and Science. ; Peer reviewed

27 páginas, 8 figuras, 3 tablas.- Versión pre-print. - The definitive version is available at: http://onlinelibrary.wiley.com/doi/10.1002/ldr.2221/abstract ; [EN] An exceptional rainfall and hydrological event occurred on 19–21 October 2012 in the central western Pyrenees and was particularly significant in the Upper Aragón River basin and its tributaries, mainly the Irati River. Analysis of historical records showed that, considered separately, the event of 19 and 20 October ranked between the second and fifth highest most extreme daily precipitation events. For the two days combined (with a total between 200 and 260 mm), the precipitation event was the most extreme 2-day event among all observation stations but one. The consequent flood destroyed part of an urban area, and a long stretch of a national road triggered landslides, enlarged the alluvial plain and caused generalised soil erosion in cultivated fields cropped with winter cereals. Badlands in the marls of the Inner Depression yielded high volumes of sediment. The floods in the tributaries were relatively moderate (return periods of 14–42 years), whereas in the Upper Aragón River, the flood corresponded to a return period of approximately 400–500 years and to 142 years at the end of the Yesa reservoir, although difficulties in estimating the discharge increased the uncertainty of these values. The Yesa and Itoiz reservoirs considerably reduced the intensity of the flood in the middle and lower Aragón River and confirmed the importance of the water level in the reservoirs when such rainfall events occur. The water storage in the Yesa reservoir increased from 16% to 53% as a consequence of the event. More integrated studies are necessary to decrease the risks associated with flood hazards. This is particularly the case in mountain areas, where the steep slopes and longitudinal gradients of the rivers shorten the concentration time of floods and increase the energy that erodes channels and riverbanks. Copyright © 2013 John Wiley & Sons, Ltd ; Support for this research was provided by the projects INDICA (CGL2011-27753-C02-01 and 02), DISPROSPEC (CGL2011-24185) and HIDROCAES (CGL2011-27574- C02-01), funded by the Spanish Ministry of Economy and Innovation; ACQWA (FP7-ENV-2007-1-212250), financed by the European Commission, and an agreement between the CSIC and the Spanish Ministry of Environment (RESEL). The research group on Geomorphology and Global Change was financed by the Aragón Government and the European Social Fund (ESF-FSE). E. Nadal-Romero and N. LanaRenault benefited from a research contract (Spanish Ministry of Economy and Innovation, Programme Juan de la Cierva). The authors acknowledge the free availability of the hydrological information from the Ebro River Authority and the help provided by the team of the Centro de Proceso de Cuenca del Sistema Automático de Información Hidrológica de la Confederación Hidrográfica del Ebro. The cartographic help from Paz Errea and Sergio Valdivielso was also acknowledged. ; Peer reviewed

32 Pag., 7 Fig. ; The hydrological and geomorphic effects of land use/land cover changes, particularly those associated with vegetation regrowth after farmland abandonment were investigated in the Central Spanish Pyrenees. The main focus was to assess the interactions among slope, catchment, basin, and fluvial channel processes over a range of spatial scales. In recent centuries most Mediterranean mountain areas have been subjected to significant human pressure through deforestation, cultivation of steep slopes, fires, and overgrazing. Depopulation commencing at the beginning of the 20th century, and particularly since the 1960s, has resulted in farmland abandonment and a reduction in livestock numbers, and this has led to an expansion of shrubs and forests. Studies in the Central Spanish Pyrenees, based on experimental plots and catchments, in large basins and fluvial channels, have confirmed that these land use changes have had hydrological and geomorphic consequences regardless of the spatial scale considered, and that processes occurring at any particular scale can be explained by such processes acting on other scales. Studies using experimental plots have demonstrated that during the period of greatest human pressure (mainly the 18th and 19th centuries), cultivation of steep slopes caused high runoff rates and extreme soil loss. Large parts of the small catchments behaved as runoff and sediment source areas, whereas the fluvial channels of large basins showed signs of high torrentiality (braided morphology, bare sedimentary bars, instability, and prevalence of bedload transport). Depopulation has concentrated most human pressure on the valley bottoms and specific locations such as resorts, whereas the remainder of the area has been affected by an almost generalized abandonment. Subsequent plant recolonization has resulted in a reduction of overland flow and declining soil erosion. At a catchment scale this has caused a reduction in sediment sources, and channel incision in the secondary streams. At the regional scale, the most important consequences include a reduction in the frequency of floods, reduced sediment yields, increasing stabilization of fluvial channels (colonization of sedimentary bars by riparian vegetation and a reduction in the braiding index), and stabilization of alluvial fans. These results demonstrate the complexity and multiscalar nature of the interactions among land use and runoff generation, soil erosion, sediment transport, and fluvial channel dynamics, and highlight the need to adopt a multiscale approach in other mountain areas of the world. ; Support for this research was provided by the projects PROBASE (CGL2006-11619/HID, Consolider) financed by the Spanish Commission of Science and Technology; ACQWA (FP7-ENV-2007-1), financed by the European Commission; and PI032/08, financed by the Aragón Regional Government. The authors also acknowledge support from the Program of Research Groups of the Aragón Regional Government, and from RESEL (the Spanish Ministry of the Environment). N. Lana-Renault and E. Nadal-Romero benefited from a research contract (I+D+I 2008–2011 National Program), funded by the Spanish Ministry of Education and Science. ; Peer reviewed