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55 Pag., 6 Tabl., 10 Fig. The definitive version is available at: http://www.ametsoc.org/ ; The occurrence of rainfalls of high magnitude constitutes a primary natural hazard in many parts of the world, and the elaboration of maps showing the hazard of extreme rainfalls has great theoretical and practical interest. In this work a procedure based on extreme value analysis and spatial interpolation techniques is described. The result is a probability model in which the distribution parameters vary smoothly in space. This methodology is applied to the middle Ebro Valley (Spain), a climatically complex area with great contrasts because of the relief and exposure to different air masses. The database consists of 43 daily precipitation series from 1950 to 2000. Because rainfall tends to occur highly clustered in time in the area, a declustering process was applied to the data, and the series of daily cluster maxima were used hereinafter. The mean excess plot and error minimizing were used to find an optimum threshold value to retain the highest records (peaks-over-threshold approach), and a Poisson–generalized Pareto model was fitted to the resulting series. The at-site parameter estimates (location, scale, and shape) were regressed upon a set of location and relief variables, enabling the construction of a spatially explicit probability model. The advantages of this method to obtain maps of extreme precipitation hazard are discussed in depth. ; The authors acknowledge financial support from the following projects: PIRIHEROS (REN2003-08678/HID); PROHISEM (REN2001-2268-C02-01/HID); BSO2002-02743; REN2002-01023-CLI and REN2003-07453, funded by Ministerio de Ciencia y Tecnología (Spain) and UE-FEDER, and "Programa de grupos de investigación consolidados" (BOA 147 of 18-12-2002), funded by Aragón Government. Research of the authors was supported by postdoctoral fellowships by the Ministerio de Educación, Cultura y Deporte (Spain). ; Peer reviewed

28 Pag., 4 Tabl., 5 Fig. The definitive version is available at: http://www.springerlink.com/content/0921-030x/ ; The paper deals with the validation and evaluation of mathematical models in natural hazard analysis, with a special focus on establishing their predictive power. Although most of the tools and statistics available are common to general classification models, some peculiarities arise in the case of hazard assessment. This is due to the fact that the target for validation, the propensity to develop a dangerous characteristic, is not really known and must be estimated from a (usually) very small sample. This implies that the two types of errors (false positives and false negatives) should be given different meanings. Related to this, a very frequent situation is the presence of prevalence (different proportion of positive and negative cases) in the sample. It is shown that sample prevalence can have a dramatic effect in some very common validation statistics, like the confusion matrix and model efficiency. Here some statistics based on the confusion matrix are presented and discussed, and the use of threshold-independent approaches (especially the ROC plot) is shown. The ROC plot is also proposed as a convenient tool for decision-taking in a risk management context. A general scheme for hazard predictive modeling is finally proposed. ; This study has been supported by the research projects "Procesos hidrológicos en cuencas pirenaicas en relación con los cambios de uso del suelo y las fluctuaciones climáticas" (PIRIHEROS, REN2003-08678/HID), and "Procesos hidrológicos en áreas seminaturales mediterráneas" (PROHISEM, REN2001-2268-C02-01/HID), funded by the Spanish Government (CICYT). ; Peer reviewed

The definitive version is available at: http://www.informaworld.com/ 31 Pag., 4 Tabl., 2 Fig. ; Inventory and monitoring of eroded areas at basin scale (Mm2) can be very useful for environmental planning and can help to reduce land degradation and sediment yield to streams. Combined use of remote sensing images and auxiliary geocoded data has been widely used for mapping various environmental features, including surface erosion. Here an example is presented in the Yesa reservoir catchment in the Spanish Pyrenees. Several combinations of radiometric data (a sequence of images from different seasons of the year) and other geocoded information, including topographical (altitude and slope) and geological maps, were compared in their ability to predict previously identified erosive features. Multinomial logistic regression was used as the classification method. The datasets were compared in terms of classification error statistics (sensitivity and specificity) using an independent random sample. The incorporation of lithological information improved the discrimination of eroded areas, but the same did not happen in the case of topographical information. Two final maps of eroded areas were obtained applying an equal predicted area rule and an equal error rate rule. ; This study has been supported by research projects PIRIHEROS (REN2003-08678/HID) and CANOA (CGL2004-04919-C02-01), funded by CICYT (Spanish Ministry of Science and Technology) and EU-FEDER, and "Programa de grupos de investigación consolidados" (BOA 48 of 20-04-2005), funded by Aragón region government. The author also wishes to acknowledge personal support by a post-doctoral grant funded by the Spanish Government Secretary for Education and Universities and the EU Social Fund. ; Peer reviewed

11 Pag., 3 Tabl., 4 Fig. The definitive version is available at: http://www.sciencedirect.com/science/journal/0169555X ; The Pyrenees, like many other mountain areas in Europe, have experienced depopulation and land abandonment during the 20th century. This has encouraged vegetation recovery in formerly occupied areas, including reforestation to promote woodland. The objective of this study is to analyse the effects of these changes on shallow landsliding, a process responsible for erosion and land degradation in many mountain areas. A sequence of aerial images reveals a slight decrease in the landslide occurrence rate in the last half of the 20th century and a parallel increase in the landslide extinction rate, i.e. the rate at which evidence of landslide activity is removed by vegetation colonisation. A logistic regression routine was used to assess the influence of land use and vegetation recovery in the occurrence of shallow landslides. The result shows that the former arable fields on the valley slopes still facilitate landsliding, even after land abandonment and revegetation by shrubs or trees. A shift in the topographic location of landslides was also detected, pointing to an increased importance of water redistribution in the slopes after prolonged rainfall periods. ; This study has been supported by the research projects PIRIHEROS (REN2003-08678/HID) and CANOA (CGL2004-04919-C02-01), funded by CICYT (Spanish Ministry of Science and Technology), and by RESEL (Spanish Ministry of Environment). Parts of the data used were collected with the support of the DAMOCLES project (EVG1-1999-00027P), funded by the European Commission. Personal support was provided by a post-doctoral grant funded by the Spanish Government Secretary for Education and Universities and the European Social Fund. ; Peer reviewed

This study has been supported by the research projects PIRIHEROS-REN2003-08678/HID, CANOA-CGL2004-04919-C02-01, REN2002-04668 and CGL2005-01625/BOS, funded by CICYT (Spanish Ministry of Science and Technology) and by RESEL (Spanish Ministry of Environment). Personal support for Y.P. was provided by Government of Aragón and CSIC and personal support for S.B. was provided by the Spanish Government Secretary for Education and Universities and the European Social Fund. ; Secondary succession after farmland abandonment has become a common process in north Mediterranean countries, especially in mountain areas. In this paper, a methodology is tested which combines Markov chains and logistic multivariate regression to model secondary succession after farmland abandonment in environments where abiotic constraints play a major role, like mountain areas. In such landscapes, a decay in the succession rate with time is usually found, as the best locations are progressively occupied. This is frequently addressed using non-stationary Markov chains. Here, we test if the combination of logistic multivariate regression with Markov chains, however, allows for spatially distributed transitions probabilities based on abiotic factors and therefore, it is able to reproduce the preferential colonization of the most favourable locations. The model is tested in the Ijuez Valley in the Spanish Pyrenees, which underwent generalized land abandonment during the 1950s. Results confirm a substantial improvement in the prediction success of the Markov-logistic model when compared to the standard Markov chain approach. As a result, the decay in the succession rate can be successfully modelled. The specific results for our study area are discussed further in an ecological context. The methodology proposed is applicable to any landscape where vegetation dynamics are constrained by environmental factors. However, the inclusion of land use as an explanatory factor would be necessary in human-managed landscapes. ; 25 Pag., 2 Tabl., 8 Fig. The definitive version is available at: http://www.sciencedirect.com/science/journal/01692046 ; Peer reviewed

9 Pags., 4 Tabls., 4 Figs. ; Rainfall erosivity refers to the ability of precipitation to erode soil, and depends on characteristics such as its total volume, duration, and intensity and amount of energy released by raindrops. Despite the relevance of rainfall erosivity for soil degradation prevention, very few studies have addressed its spatial and temporal variability. In this study the time variation of rainfall erosivity in the Ebro Valley (NE Spain) is assessed for the period 1955–2006. The results show a general decrease in annual and seasonal rainfall erosivity, which is explained by a decrease of very intense rainfall events whilst the frequency of moderate and low events increased. This trend is related to prevailing positive conditions of the main atmospheric teleconnection indices affecting the West Mediterranean, i.e. the North Atlantic Oscillation (NAO), the Mediterranean Oscillation (MO) and the Western Mediterranean Oscillation (WeMO). ; This work has been supported by research projects CGL2011- 24185 financed by the Spanish Ministry of Science and Innovation (CICYT) and the European Regional Development Fund (ERDFFEDER), 2010CZ0021 financed by the Spanish National Research Council (Consejo Superior de Investigaciones Científicas-CSIC) and the Czech Academy of Sciences, and "Grupo de Investigación E68: Geomorfología y Cambio Global" financed by the Aragón Government and the European Social Fund (ESF-FSE). Research of M. A.-M. was supported by a JAE-Predoc grant from the Spanish National Research Council (Consejo Superior de Investigaciones Científicas-CSIC). ; Peer reviewed

47 Pags.- 9 Figs.- 1 Tabl. ; The Pyrenees are the main source of water for a large region in Southern Europe. In recent decades, streamflow and snow accumulation in these mountains have decreased, and climate models predict that further reductions in water will threaten the sustainability of downstream regions. This article presents a cascading multi-model and multi-scenario approach to assess how future climate change may affect the hydrology and water management of Pyrenees-dependent systems. In particular, we combined future climate projections and management scenarios and applied them to the Gállego-Cinca River System in the Ebro River Basin of Spain. We developed a hydrologic model for the headwaters of this system (the source of most of the water), and then used a management model to simulate reservoir operation and water allocation among the different agricultural demand units of this system, the largest irrigated region in Spain. We assessed future headwater streamflow for 22 climate models, and translated this climate signal into a management model by using a delta change approach. Finally, we evaluated the performance and sustainability of the system with indicators based on the frequency, duration, and magnitude of the supply deficit. The results show that use of the current planned management scenarios will threaten to the system's future sustainability, especially for irrigated agriculture. These results indicate a need to revise current water resource planning strategies in this region, and to establish long-term, robust, and sustainable measures for adaptation to climate change. ; Funding for this research was provided by the project EFA210/16/PIRAGUA co-founded by the European Regional Development Fund (ERDF) through the Interreg V Spain-France-Andorre Programme (POCTEFA 2014-2020) of the European Union, by the project INNOMED co-funded by the Agencia Estatal de Investigación of Spain in the framework of the ERA-NET WaterWorks2015 Cofunded Call (project INNOMED). This ERA-NET is an integral part of the 2016 Joint Activities developed by the Water Challenges for a Changing World Joint Programme Initiative (Water JPI) as a result of a joint collaborative effort with the Joint Programming Initiative on Agriculture, Food Security and Climate Change (FACCE JPI). Also, this work was supported by Fundación Biodiversidad of the Spanish Ministerio para la Transición Ecológica. ; Peer reviewed

15 Pags. - 3 Figs. The definitive version, with Appendix and Supplementary Data, is available at: http://www.sciencedirect.com/science/journal/13648152 ; Daily precipitation datasets are usually large, bulky and hard to handle, but they are of key importance in many environmental studies. We developed a tool to create custom datasets from observed daily precipitation records. Reference values (RV) are computed for each day and location using multivariate logistic regression with altitude, latitude and longitude as covariates. The operations were compiled in an Open Source R package called reddPrec. The reddPrec package consists of a set of functions used to: i) apply a comprehensive quality control over original daily precipitation datasets, flagging suspect data based on five predefined criteria; ii) fill missing values in original data series by estimating precipitation values using the 10 nearest observations for each day; and iii) create new series and gridded datasets in locations where no data were recorded. ; This study was supported by research projects CGL2012-31668, CGL2015-69985-R, CGL2011-24185 and CGL2014-52135-C3-1-R, financed by the Spanish Ministerio de Economía y Competitividad (MINECO) and FEDER-ERDF funds. We were financially supported by the Government of Aragón through the 'Programme of research groups' (groups 'H38, Clima, Cambio Global y Sistemas Naturales' and 'E68, Geomorfología y Cambio Global'). ; Peer reviewed

The changes of landscape (1927–2003), discharge regime and anthropic activities with the river-floodplain of one reach at the Middle Ebro River (NE Spain) were investigated with the objective to identify the factors that best explain the natural ecotope succession and propose a realistic restoration option with consideration of the landscape dynamics during the last century and the socio-economic context. Our results indicate that hydrological and landscape patterns have been dramatically changed during the last century as a consequence of human alteration of the fluvial dynamics within the studied reach. The magnitude and variability of river discharge events have decreased at the end of the last century, and flood protection structures have disrupted the river floodplain connectivity. As a result, the succesional pathways of riparian ecotopes have been heavily modified because natural rejuvenation no longer takes place, resulting in decreased landscape diversity. It is apparent from these data that floodplain restoration must be incorporated as a significant factor into river management plans if a more natural functioning wants to be retrieved. The ecotope structure and dynamics of the 1927–1957 period should be adopted as the guiding image, whereas current hydrologic and landscape (dykes, raised surfaces) patterns should be considered. Under the current socio-economic context, the more realistic option seems to create a dynamic river corridor reallocating dykes and lowering floodplain heights. The extent of this river corridor should adapt to the restored flow regime, although periodic economic investments could be an option if the desired self-sustained dynamism is not reached. ; The research was funded by the Department of the Environmental Science, Technology and University –Aragon government (Research group E-61 on Ecological Restoration)- and MEC (CGL2005-07059). The Spanish Research Council (CSIC) granted Alvaro Cabezas through the I3P program (I3P-EPD2003-2), which was financed by European Social Funds (UE). ; Peer reviewed

11 páginas, 4 tablas, 4 figuras.-- El Pdf es la versión pre-print. ; The temporal evolution of vegetation activity on various land cover classes in the Spanish Pyrenees was analyzed. Two time series of the normalized difference vegetation index (NDVI) were used, corresponding to March (early spring) and August (the end of summer). The series were generated from Landsat TM and Landsat ETM+ images for the period 1984–2007. An increase in the NDVI in March was found for vegetated areas, and the opposite trend was found in both March and August for degraded areas (badlands and erosion risk areas). The rise in minimum temperature and the time variation of the cloud cover during the study period appears to be the most important factors explaining increased NDVI in the vegetated areas. In degraded areas, no climatic or topographic variable was associated with the negative NDVI trend, which may be related to erosion processes taking place in these regions. ; This research was supported by the projects CGL2006-11619/HID, CGL2008- 00831/BTE and CGL2008-01189/BTE (Spanish Commission of Science and Technology and FEDER), ACQWA (FP7-ENV-2007-1- 212250; VII Framework Program of the European Commission), 'Las sequías climáticas en la cuenca del Ebro y su respuesta hidrológica' ('Obra Social La Caixa' and the Aragón Government), and 'Programa de grupos de investigación consolidados' (Aragón Government). The first author was supported by a scholarship from The National Council for Science and Technology of Mexico (CONACYT). ; Peer reviewed

A new multiscalar drought dataset, the SPEIbase, made available to the scientific and management community is presented. The multiscalar character of the dataset allows finding the most appropriate time scale of interest for a specific application, so potential uses of the dataset range over a wide variety of disciplines. The dataset (in three file formats) is distributed under an open license. Further work includes updating the dataset past December 2006, depending on the data availability. ; This work has been supported by the research projects CGL2008-01189/BTE and CGL2006-11619/HID, funded by the Spanish Commission of Science and Technology and FEDER; EUROGEOSS (FP7-ENV-2008-1-226487) and ACQWA (FP7-ENV-2007-1- 212250), funded by the VII Framework Programme of the European Commission; and "Las sequías climáticas en la cuenca del Ebro y su respuesta hidrológica" and "La nieve en el Pirineo aragonés: Distribución espacial y su respuesta a las condiciones climática," funded by "Obra Social La Caixa" and the Aragón Government. ; Peer reviewed

7 Pag., 6 Fig., 2 Tabl. ; Shifting agriculture has been practiced over large areas in middle-latitude mountains in the Mediterranean basin during periods of strong demographic pressure. On average, such land accounted for about 22.8% of the total cultivated area in the Central Spanish Pyrenees at the beginning of the 20th century. The use of experimental plots between 1992 and 2003 demonstrated that shifting agriculture increased overland flow, suspended sediment, and solute concentration. Total soil loss was about 14 times higher on plots under shifting agriculture than on plots under dense shrub cover, and almost 3 times higher than on permanent sloping fields. Erosion rates ranged between 0.1 and 1.4 t/ha/yr. The abandonment of shifting agriculture practices resulted in rapid plant recolonization and a decrease in runoff and soil erosion. Nevertheless, severe geomorphic processes were found to be still active several decades after abandonment, explaining landscape degradation and the occurrence of shallow landslides. ; Support for this research was provided by the following projects: PIRIHEROS (REN2003-08678/HID), CANOA (CGL2004-04919-C02-01) and EROFUEGO (REN2002-00133GLO), funded by CICYT, the Spanish Ministry of Science and Technology, and by RESEL (the Spanish Ministry of the Environment). Personal support for Santiago Beguería was provided by the Spanish Government Secretary for Education and Universities and the European Social Fund. ; 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

9 Pag., 5 Fig. ; We discuss here shortcomings of the PDSI in adequately modeling the soil water balance, and its limited ability to quantify and monitor droughts of different types. Conversely, we describe the advantages of statistically based drought indices in analyzing the spatial and temporal variability of drought, identifying drought impacts in a variety of systems, and monitoring drought conditions in real time. ; This work has been supported by the research projects CGL2006‐11619/HID, CGL2008‐01189/BTE, CGL2011‐27574‐ CO2‐02 and CGL2011‐27536 financed by the Spanish Commission of Science and Technology and FEDER, EUROGEOSS (FP7‐ENV‐2008‐1‐ 226487) and ACQWA (FP7‐ENV‐2007‐1‐ 212250) financed by the VII Framework Programme of the European Commission, "Efecto de los escenarios de cambio climático sobre la hidrología superficial y la gestión de embalses del Pirineo Aragonés" financed by "Obra Social La Caixa" and the Aragón Government and "Influencia del cambio climático en el turismo de nieve", CTTP01/10, Financed by the Comisión de Trabajo de los Pirineos. ; Peer reviewed