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The aim of this study is to investigate the influence of weathering processes on the distribution of n-alkanes in unweathered and weathered samples of badland material. Organic matter (OM) of both the weathered and unweathered zones in badland environments is derived from the same sources such any differences between the n-alkane pattern of the two zones can be attributed to the impact of weathering processes under different climate conditions. Organic geochemical and mineralogical characterizations were employed to investigate twenty-one samples from weathered badland environments in Italy, Spain, and Canada that originally derive from marine, distal alluvial, and fluvial depositional settings, respectively. According to the distribution of n-alkanes and diterpanes, unweathered samples from Italy have an original mixed aquatic-terrestrial origin of OM, with a variable (low to moderate) contribution of terrestrial plants as precursors, while unweathered samples from Spain predominantly contain OM originating from submerged/ floating macrophytes deposited under reducing conditions. Unweathered samples from Canada predominantly consist of terrigenous OM. Intensity of changes in n-alkanes distribution when subjected to weathering depends on the type of precursor biomass and quantity of smectite. Predominantly terrigenous OM under semi-arid conditions shows the highest affinity for adsorption is in contact with smectite surfaces. Mid- and long-chain odd n-alkanes have a tendency to build colloidal particles with polar organic compounds such as fatty acids by strong binding and thus their preservation from degradation is possible.

Badlands are highly erosive landforms of dissected morphology, which can be found on soft rocks and unconsolidated sediments, with little or no vegetation, that are useless for agriculture. The erosion rates of these areas are high, causing important environmental and economic problems. For that reason, detecting the main conditioning factors that control badland occurrence and identifying susceptible areas is higly important to prevent soil erosion phenomena and their negative consequences.This work attempts to assess badland susceptibility and their governing factors at a multi-scale level, using a random forest (RF) modelling approach. Previous RF-based research have demonstrated that RF modelling is a powerful tool for making predictions in the same spatial context and scale where the model has been trained. However, upscaling RF-modelling results to obtain accurate predictions in other, more extensive spatial contexts than that used for model training, remains an important challenge.For that, the Upper Llobregat River Basin (ULRB, 504.8 km2) and Catalonia region (CAT, 32000 km2) have been selected as study areas. We have evaluated the viability of training a RF model for the analysis of badland suceptibility in the small spatial context of the ULRB, and further testing it to the more extensive spatial context of CAT. Revealing the most important factors that control badland distribution in the territory has been another goal in the present study. Eleven governing factors and two badland inventories developed for these study areas have been used for model training and testing. Model performance has been analyzed through validation tests and three different evaluation metrics: AUC, Kappa coefficient and accuracy. The outcomes of this work manifest that the two variables that have the most important relevance for badland occurrence are lithology and NDVI. In addition, our results showed that upscaling RF model results defined in the ULRB to the more extensive spatial context of CAT in order to predict badland occurrence, it’s possible but not ideal. Last, badland susceptibility maps of ULRB and Catalonia have been obtained with a very high accuracy (96% and 97% respectively), confirming the feasibility and uselfuness of RF approach for badland susceptibility assessment.

The organization and function of forest ecosystems is changing at an unprecedent rate under the influence of external drivers, such as climate change and human uses. In this context of change, the increasing frequency, intensity and duration of droughts that affect the Mediterranean basin urges to evaluate forest vulnerability to drought and their effects for the long-term stability of these ecosystems. In this study, we explore the responses and factors that control the resilience of holm oak (Quercus ilex) woodlands to recent extreme droughts during 2000-2019, using a remote sensing approach over a broad scale climate aridity gradient that extends from sub-humid to semi-arid climate conditions over 100,000 km2 in eastern Spain. Overall, our results indicated that climate aridity and forest structure largely control the resistance, recovery and resilience of the studied holm oak woodlands to drought, which are also affected by drought intensity and both pre- and post-drought hydric conditions. We found that Q. ilex woodlands located in the dry edge of the explored climate aridity gradient showed a high sensitivity to extreme drought. Their resistance, assessed as the capacity of the woodlands to maintain primary production during drought, was low. They also showed a poor resilience, characterized by a low capacity to fully recover their pre-drought production levels. Contrarily, holm oak woodlands in sub-humid areas of the study region, where wetter climate conditions may alleviate water stress during dry periods, showed a high resistance and resilience to the effects of droughts. Drought vulnerability was particularly high for dense holm oak stands developed under semi-arid climate conditions, where strong competition for scarce water resources largely increased the negative effects of extreme drought on landscape-level ecosystem production. We also discuss the implications of these results for adaptive management of holm oak forests in the present context of climate change.

As part of the earth's dynamic systems, badland landscapes are chiefly generated by the interaction between bedrock weathering, climate seasonality, and the controversial contribution of the hillslope and fluvial erosion processes. Although contemporary definitions clearly point out that badland initiation is a function of overland-flow-dominated gully channels, gravitational processes-dominated mass movements, and subsurface processes-driven piping, the following related questions remain to be tackled regarding their topographic position in the landscape: (1) Are the badland landforms signature of hillslope or fluvial erosion domain? (2) How do climate and regional settings (i.e., macro landforms, homogenous or heterogenous lithologies, etc.) influence the topographic position of badlands? To address these questions, we have selected climatically distinct badlands from different continents where; digital elevation models are available: Utah and South Dakota (USA), Upper Llobregat and Murcia (Spain), Northern Apennines and Basilicata (Italy), Mediterranean and Plateau – Margin Transition Badlands (Turkey), and Southern Taiwan. The badland boundaries were visually inspected and manually digitized based on diagnostic morphologic indicators. We have utilized the slope and drainage area relationship by using a 5m digital terrain model to identify topographic thresholds at TopoToolbox, a MATLAB-based software for topographic analysis. Preliminary results show that most badland areas occupy a maximum of 104 to 105 m2 contribution area in the landscapes. Although contribution areas relatively represent uniform thresholds in the sites, the local gradient (S), which is proportional to the contribution area, tends to be higher in the sub-humid mountainous badlands (Upper Llobregat, Northern Apennines) and wet tropical SW Taiwan than in semi-arid badlands (Basilicata, Murcia). We conclude that the topographic signature of badlands in the context of the sub-catchment scale may depict an appropriate instance of a transitional domain from a diffusive erosional process to a fluvial erosion process. Our findings may serve as a foundation for a better understanding of the classification and automatic detection of badland landscapes, also known as erosional hot spots.This study has been produced benefiting from the 2232 International Fellowship for Outstanding Researchers Program of the Scientific and Technological Research Council of Turkey (TUBITAK) through grant 118C329 and TUBITAK 2214-A International Research Fellowship Programme.

Ecohydrologically suitable microsites, such as surface depressions and micro-topographical barriers acting as sink patches intercepting and infiltrating runoff, as well as nurse shrubs have largely been proposed as tools to improve the establishment of tree vegetation in Mediterranean reclaimed landscapes and other degraded dryland environments. We analyze the impact of sink patches and nurse (Genista scorpius) shrubs developed in Mediterranean-dry reclaimed mining hillslopes (Utrillas field site, central Spain) on seedling performance up to 8 years after plantation of two tree species with contrasted water-use strategies: Pinus nigra, a drought avoider species, and Quercus ilex, a drought tolerant species. Nurse shrubs enhanced early establishment of seedlings in shaded spots under its canopy. Further, sink patches ameliorated the survival of both species, although only increased plant growth during wet years that promoted source-to-sink transference of surface water resources as surface runoff. The survival and growth of P. nigra seedlings were strongly constrained during dry periods, resulting in a high cumulative mortality after 8 years regardless of microsite. Q. ilex showed a better performance during the experiment, keeping the positive effects of suitable microsites on plant survival after 8 years of plantation. Overall, our results encourage the use of ecohydrologically suitable microsites that concentrate water resources and nurse shrubs that ameliorate local conditions as key spots for introducing late-successional tree species in Mediterranean-dry reclaimed mining sites. Our results also indicate that seedling functional strategy to cope with drought is a critical factor conditioning plantation performance, therefore constituting a fundamental species selection criterion for restoration actions in Mediterranean areas, especially under effects of climate change.

Scenarios serve science by testing the sensitivity of a system and/or society to adapt to the future. In this study, we present a new land use scenario methodology called ScenaLand. This methodology aims to develop plausible and contrasting land use and management (LUM) scenarios, useful to explore how LUM (e.g. soil and water conservation techniques) may affect ecosystem services under global change in a wide range of environments. ScenaLand is a method for constructing narrative and spatially explicit land use scenarios that are useful for end-users and impact modellers. This method is innovative because it merges literature and expert knowledge, and its low data requirement makes it easy to be implemented in the context of inter-site comparison, including global change projections. ScenaLand was developed and tested on six different Mediterranean agroecological and socioeconomic contexts during the MASCC research project (Mediterranean agricultural soil conservation under global change). The method first highlights the socioeconomic trends of each study site including emerging trends such as new government laws, LUM techniques through a qualitative survey addressed to local experts. Then, the method includes a ranking of driving factors, a matrix about land use evolution, and soil and water conservation techniques. ScenaLand also includes a framework to develop narratives along with two priority axes (contextualized to environmental protection vs. land productivity in this study). In the context of this research project, four contrasting scenarios are proposed: S1 (business-as-usual), S2 (market-oriented), S3 (environmental protection), and S4 (sustainable). Land use maps are then built with the creation of LUM allocation rules based on agroecological zoning. ScenaLand resulted in a robust and easy method to apply with the creation of 24 contrasted scenarios. These scenarios come not only with narratives but also with spatially explicit maps that are potentially used by impact modellers and other end-users. The last part of our study discusses the way the method can be implemented including a comparison between sites and the possibilities to implement ScenaLand in other contexts., This work and the postdoctoral grant of AV Pastor benefits from the financial support of the MASCC project through ARIMNET2, an ERA-NET funded by the European Union’s Seventh Framework Program for research, technological development and demonstration under grant agreement no. 618127. In addition, MMH is beneficiary of a Serra Hunter fellowship (UB-LE-9055) funded by the Generalitat de Catalunya. JJK received the financial support through CESAM (UIDP/50017/2020 + UIDB/50017/2020 + LA/P/0094/2020), from FCT/MCTES through national funds (OE). The authors would like to thank Marie Castellazi for her valuable contribution and shared experience in building land use scenarios, Dominique Rollain for his valuable contribution to the Roujan scenarios and Francesc Gallart for his valuable contribution to the Can Vila study case. We would like to thank all the other persons that contributed to the related surveys. Finally, we would like to send our homage to Dr Yves Le- Bissonnais, a brilliant researcher in the erosion discipline and coauthor of this research article who passed away in 2021.

Badlands are areas with limited vegetation, reduced or no human activity, and a great variety of geomorphic processes present. Besides lithology, the climate has a crucial role in the initiation and development of badlands. Controlled conditions during laboratory experiments provide detailed insight into processes that occur in the nature. Many studies have shown that the type and content of clay minerals, specifically presence of smectite is important for predicting the behavior of sediments subjected to different weathering treatments like freezing, thawing, wetting, and drying.This study is aimed at comparing changes in physico-chemical properties of sediments caused by simulations of climatic conditions. For these experiments, three unweathered samples with different mineralogical content were taken from the Vallcebre and Bagà badlands in Spain. Besides quartz and calcite as dominant minerals, one sample contained smectite and gypsum, the second smectite, and the third neither smectite nor gypsum. The experiment was set up in a way that each sample had three sub-samples from which one was subjected to rain, the second to snow, and the third was the control sample. The experiment had two parts. In the first part, after simulation of rain (~140 ml) or snow (~150 g), samples together with a control sample were placed in a climate chamber at a temperature of -3 °C. After initial 15 cycles, in the second part of the experiment, all samples regardless of the previous treatment were subjected to rain (~140 ml), after which together with the control sample were placed in a climate chamber at a temperature of 50 °C. These treatments were repeated 8 times. Throughout the experiment, after each cycle, samples were photographed for monitoring surface changes, while the leached solution was collected and its volume, pH, electrical conductivity (EC), and ion concentrations were measured. Field Emission Scanning Electron Microscopy (FESEM) results showed that the changes in microstructure occurred after weathering experiments, while Brunauer-Emmett-Teller (BET) surface area analysis confirmed that the sample with only smectite had the highest specific surface. Also, it was corroborated that temperature without simulation of rain or snow does not affect the decomposition since the control samples remained intact during the whole experiment. Results have shown that snow is a more destructive agent, especially for the sample with smectite. Due to the content of gypsum, which increases the weathering resistance of the material, the sample with smectite and gypsum has shown a lower degree of degradation than the sample with only smectite, while sample without smectite and gypsum has shown the lowest degradation of the structure. Furthermore, the sample with smectite and gypsum has shown significantly different values of leachate pH, and EC. The concentration of sulphate was the highest in the sample with smectite and gypsum, which is a consequence of the dissolution of gypsum. The obtained results confirm that the response of sediment to different climatic factors depends on their mineral and physico-chemical properties and provide a basis for further research of prediction land degradation in conditions of climate change.

The use of ecohydrologically suitable microsites, such as sink patches (i.e. zones intercepting and infiltrating runoff) and nurse shrubs, have largely been proposed as tools to improve the establishment of late-successional trees in Mediterranean reclaimed landscapes. Nonetheless, this technique needs to be accurately tested along with the influence of seedling water-use strategy. To that purpose, we monitored the short- and mid-term (i.e. 4 and 8 years, respectively) influence of sink patches and nurse shrubs (Genista scorpius) on seedlings of two species with contrasted water-use strategies, Pinus nigra, a more drought avoider and isohydric species, and Quercus ilex, a more drought tolerant and anisohydric species. In the short term, G. scorpius shrubs enhanced the establishment of seedlings planted in shaded spots under its canopy. This positive interaction was more relevant for Q. ilex in drier years, while P. nigra was more facilitated in wetter years. Sink patches ameliorated the survival of both species, but only promoted greater growth during wetter years. P. nigra seedlings showed a high sensitivity to precipitation reduction. Their survival and growth were strongly constrained in dry years, resulting in a very high cumulative mortality at the end of the 8-year study period regardless of the microsite the seedlings were planted in. Q. ilex showed better seedling performance than P. nigra in the mid-term, keeping also the positive effects of suitable microsites on plant survival in the mid-term, after 8 years of plantation. Our results support the use of suitable microsites that ameliorate ecohydrological conditions as key spots for enhancing ecological succession in reclaimed mining sites, particularly the use of G. scorpius as nurse shrub for improving Q. ilex seedling establishment and growth. Our results also suggest that seedling functional strategy to cope with drought is a critical factor conditioning the overall plantation performance in the mid-term. Thus, seedling water-use strategy should constitute a key species selection criteria in future restoration programs focused on Mediterranean ecosystems, especially under climate change. This work was funded by the project CGL2010-21754-C0-02 from the Spanish Ministry of Economy and Competitiveness. EV is supported by the Spanish Ministry of Economy and Competitiveness within project ALTERACLIM (CGL2015-69773-C2-1-P). MMH is beneficiary of a Serra Hunter fellowship on Physical and Environmental Geography funded by the Generalitat de Catalunya (UB-LE-9055).

Empirical evidence of the vulnerability of dryland ecosystems to suffer abrupt changes in response to global change is highly needed to assess the applicability of threshold models, understand the underlying mechanisms and anticipate the onset of abrupt shifts. We study the onset of abrupt changes in Mediterranean holm oak (Quercus ilex) woodlands, by analyzing the combined effect of past human disturbance (mainly deforestation) and aridity on the functional state of these ecosystems. We determine ecosystem state in terms of herbaceous/woody species ratio, species richness and soil properties related to carbon and nitrogen cycling and microbial activity. The influence of both drivers was determined along spatial gradients of past human disturbance (from lightly to highly disturbed areas) and aridity (three levels: sub-humid, dry-transition, semi-arid). Our results show a strong interaction between aridity and past human disturbance on soil and vegetation properties. As disturbance increased, soil function decreased linearly in semi-arid and dry-transition conditions, but the trend was non-linear in sub-humid conditions. The latter showed a sharp decline at low-to-moderate disturbance intensity followed by a gentle recovery at higher intensities. These patterns were consistent for all soil properties. Structural changes in vegetation along the disturbance gradient, from open woodlands to shrublands in semi-arid and dry-transition conditions and from dense woodlands to grasslands in sub-humid conditions accompanied the linear vs non-linear patterns in soil function, respectively. Our results evidenced the existence of a critical climatic threshold in the boundary between sub-humid and dry-transition conditions, where the ecosystem switched from a fertile grassland to a highly degraded shrubland at moderate-to-high levels of disturbance (shrub encroachment), losing its capacity to buffer the effects of increasing disturbance. We propose a conceptual model illustrating the ecological mechanisms that may be underlying the onset of such abrupt shift., This study was made possible thanks to the financial support of the Spanish Ministry of Economy and Competitiveness (MEC, project INDICAR/CGL2013-42213-R) and the Spanish Ministry of Science, Innovation and Universities (MCIU)/Spanish State Research Agency (AEI)/European Regional Development Fund (ERDF) (project caRRRascal/RTI2018-095037-B-I00).

Badlands are extremely rugged, outstanding landscapes that can be seen in all ice-free climate regions over erosion-susceptible unconsolidated materials, and they have drawn attention with their spectacular and iconic forms. Unlike nearly all badlands researches conducted at the experimental site and watershed scale, so far, the broader-scale evaluation has been neglected in the analysis of badland distribution, characteristics, and dynamics. Our study provides an integrative new insight into badland landscapes by investigating the distribution, characteristics and controlling factors of Turkish badlands on a broad, regional scale. We inventoried Turkish badlands using aerial imagery and studied their distribution using K-means clustering, an unsupervised machine learning algorithm, based on a set of major conditional geo-environmental factors that control the regional distribution and characteristics of badlands, including tectonics, lithology, topography, climate, and vegetation. Here, we identified, a total of 4494 km2 of badland areas which are non-uniformly distributed across Turkey, substantially clustered in the Central Anatolian Plateau (CAP). According to our regional analyses, we have determined a total of five badland regions comprising three major types classified as Semi-arid, Mediterranean, and Montane (humid), together with two transitional types in-between the Semi-arid and Montane badland regions. Our results indicate that temperature seasonality (0.83), mean annual precipitation (0.83), and precipitation seasonality (0.76) are predominantly assigned to the badlands clusters. The clastic rocks are revealed as the most crucial and inevitable factor for the development of Turkish badlands, which are represented in a wide geologic time-scale (Cretaceous to Quaternary) and diverse lithological units (i.e., lacustrine, volcaniclastics, and terrestrial). Neogene and Paleogene terrestrial clastics (77 %) constitute the majority of the lithologic settings of these badland landscapes. The active and complex tectonic history of Turkey has portrayed the fundamental frame of the identified badland regions, by providing a susceptible environment (i.e., development of sedimentary basins) and promoting badland development through successive base-level changes. Furthermore, tectonically-modulated (i.e., formation of orogenic belts, and uplifting of CAP) climate dynamics outline the distribution pattern and differentiation of the regional characteristics of badlands in Turkey. Overall, our regional-scale approach to badland mapping and regional synthesis may decipher not only the tectonic and climatic conditions of the identified badlands regions, but it may also contribute to the implementation of future effective strategies for the detection and mapping of erosion susceptible and high sediment flux areas in very broad spatial contexts of similar unexplored territories., The authors are thankful to editor Arnaud Temme and three anonymous reviewers for their useful and constructive comments. This study is supported by the 2232 International Fellowship for Outstanding Researchers Program of the Scientific and Technological Research Council of Turkey (TUBITAK) through grant 118C329. The financial support received from TUBITAK does not indicate that the content of the publication is approved in a scientific sense by TUBITAK. MMH is a Serra Hunter fellow funded by the Generalitat the Catalunya (UB-LE-9055). The authors thank to Orkan Ozcan, Ali Mohammadi, Serdar Yeşilyurt, Cihan Yıldız, Onur Altınay, and Tunahan Aykut for their support during the fieldworks.

Traditional cultivation terraces are one of the most ancient and conspicuous agricultural landscapes in mountain and hilly regions of the Mediterranean basin. Spreading out from Asia, the first terraces in the Mediterranean region date from the Bronze Age and the classical Hellenic and Roman periods, reaching their greatest spatial extent during the eighteenth and nineteenth centuries. Under optimum management, these systems contribute to the conservation of soil and water resources by increasing infiltration and decreasing sediment yield. However, traditional management and cultivation ceased on many terraced landscapes of the northern-shore Mediterranean countries during the twentieth century, with variable results. An extensive bibliographic review and meta-analysis was carried out to explore the main effects of land abandonment of Mediterranean agricultural terraces on local hydrological and geomorphological processes. Our results point to the development of vegetation cover and degradation of terraced structures (e.g., walls, terrace risers, channels) as the main critical factors controlling the hydrological behaviour (i.e., runoff production and hydrological connectivity) of abandoned terrace systems. Severe geomorphological problems, in the form of intense surface erosion, aggressive piping and gullying, occurred under special climatic (semi-arid climate), lithologic (dispersive marls) and structural (high vertical hydraulic gradient) conditions. Dense colonization by vegetation proved to be of major importance for controlling surface erosion. Vegetation, however, showed a limited capacity to control the activity of mass movements in most cases. Mass movements in the form of small soil slips primarily affected long-abandoned terraces in hillslope concavities and valley bottom positions that concentrate (surface and subsurface) water fluxes and show recurrent soil saturation. In humid terraced landscapes characterized by high hillslope gradients and terrace risers, the most devastating effects of mass movements took place in the form of debris slips and terrace cascading landslides triggered by extreme rainfall. A variety of management options (non-intervention, stewardship of natural rewilding processes and active rehabilitation) can be applied, depending on vegetation development potential, site hydro-geomorphic vulnerability and local socio-economic interests. Effective conservation approaches will be required to preserve the environmental, socio-cultural and historical values of these ancient anthropogenic landscapes. © 2019 Elsevier B.V., This study is supported by the MASCC project funded by the European Union 7th Framework Programme (ARIMNet2, grant agreement 618127) and by the MASCC-DYNAMITE (PCIN-2017-061/AEI), TransHyMed (CGL2016-75957-R, AEI/FEDER, EU) and ESPAS (CGL2015-65569-R) projects funded by the State Research Agency (AEI) of the Spanish Ministry of Science, Innovation and Universities (MCIU) and the Spanish Ministry of Economy and Competitiveness (MEC). Mariano Moreno-de-las-Heras is beneficiary of a Juan de la Cierva fellowship (IJCI-2015-26463) funded by the MEC. We are grateful to Jean Claude Latombe, José Angel Llorente, Manuel López-Vicente and Ruth Manfredi, who kindly provided photographs of terraced landscapes and erosive processes for this study. We also thank the Editor, Scott A. Lecce, and four anonymous reviewers for their thoughtful comments, as well as Michael Eaude for language corrections.

Changes in hydro-geomorphic connectivity have been previously linked to catastrophic shifts in landscape structures and function leading to irreversible degradation. Here we present evidence and new observations to better understand the link between connectivity of water and sediments and possible phase transitions for the case of semiarid ecosystems at the catchment and hillslope scales. We first focus on rangelands, where coevolving vegetation and landform structures lead to a distinct connectivity pattern responsible for the healthy functioning of the system. Positive feedbacks, triggered by disturbances in vegetation, water or sediment structures can alter the hydro-geomorphic connectivity leading to degradation. Our results for rangelands in Australia, from both simulations and observations, suggest that an increase in connectivity beyond a threshold may lead to irreversible degradation, meaning that the system return to a functional state is unlikely without extensive management interventions. We also analyse the case of semi-arid floodplain wetlands of the Murray-Darling Basin, where we observe that dis-connectivity during droughts promote terrestrial vegetation encroachment and degradation. Simulations and observations also indicate the presence of thresholds beyond which the recovery of the system is unlikely without interventions.

Badland areas are present in all continents, excluding Antarctica, and play a critical role in establishing local erosion and sedimentation rates. The presence of unconsolidated rocks (e.g., marls, sandstone, mudstone etc.) is a major driver controlling the distribution of badlands, which together with other environmental components, such as climate, tectonics, vegetation, and topography, determine their forms and processes. The mutual interaction of controlling factors in badlands areas provides a basis for developing a holistic approach to clarify their distribution patterns. Turkey's geodynamic evolution has led to the emergence of marine sedimentary rocks, pyroclastics, and continental clastics, especially in line with the uplift of the Anatolian Plateau and volcanism during the last 8 Ma.This study aims to explore the country-scale distribution of badlands and the controlling factors of this badland distribution in Turkey. Remarkably wide badlands landscapes (4494 km2) have been visually inspected using Google Earth ProTM to further digitize and extract geomorphological units by applying high-resolution multispectral images provided by WorldView-4/Maxar Technology and CNES/Airbus. To obtain exact boundaries, we eliminated contiguous flat areas surrounding the identified badlands by using red relief image map (RRIM) mosaics that express surface concavity and convexity combined with topographic slope derived from a digital elevation model of 5-m spatial resolution. Last, to determine the controlling factors of badlands distribution, we have compiled a global data set comprising 1-km resolution layers of mean annual precipitation, temperature and precipitation seasonality, aridity, NDVI, rainfall erosivity factor, elevation, and majority values of regional lithology in sub-catchments units. The enhanced investigation of the complex relationship that expresses the controlling factors of badlands distribution, has been conducted by K-means unsupervised cluster analysis.Our comprehensive regional analyses exploring the distribution and environmental attributes of major Turkish badlands identified five different groups or clusters of badlands that display spatial coherence with climatic and tectonic settings. We argue that Turkey's climatic and topographic transition zones, varying from Mediterranean climate dominated areas to the more arid Central Anatolian Plateau, and tectonically‑induced topographic barriers play a relevant role in discriminating these groups of badlands. Moreover, the Anatolian diversity of sedimentary rocks, which consists of Neogene and Paleogene continental clastics, volcano clastics & pyroclastics, and lacustrine deposits, makes an essential contribution to the identified, extensive badland distribution.This study has been produced benefiting from the 2232 International Fellowship for Outstanding Researchers Program of the Scientific and Technological Research Council of Turkey (TUBITAK) through grant 118C329. The financial support received from TUBITAK does not mean that the content of the publication is approved in a scientific sense by TUBITAK.

Vegetation not only controls but is also controlled by erosion processes. This tight feedback effect leads to the coevolution of vegetation and erosion patterns that modulate landform shape, and regulate many other landscape processes. These tight interactions are particularly important in semiarid landscapes. We have studied these interactions using a landform evolution model that accounts for the effect (and feedbacks) of spatially and temporally varying hydrologic and vegetation patterns.We apply the modelling framework to improve our understanding of the coevolution of landforms and vegetation patterns in different semiarid landscapes in Australia. The vegetation of the selected sites is Acacia Aneura (Mulga) which covers vast areas of Australia. These sites display a sparse vegetation cover and strong patterns of water redistribution, with sources located in the bare areas and sinks in the vegetation patches which characterize the observed hydrologic connectivity. This effect triggers high spatial variability of erosion/deposition rates that affects the evolving topography and induces feedbacks to the dynamic vegetation patterns. We run simulations for 1000 years using local rainfall and erosion and vegetation parameters previously calibrated for similar sites in the Northern territory. Our numerical modelling results are validated by comparing simulated and observed patterns of vegetation and landforms obtained from satellite, airborne remote sensing and field data. We further investigate the effect of alterations in hydrologic connectivity induced by climate change and/or anthropogenic activities, which affect water and sediment redistribution and can be linked to loss of resources leading to degradation.Our simulations are able to reproduce observed banded vegetation and landform patterns for the Northern territory in Australia. We show that an increase in hydrologic connectivity can trigger changes in vegetation patterns inducing feedbacks with landforms leading to degraded states. These transitions display non-linear behaviour and in some cases can lead to thresholds with an abrupt reduction in productivity. Critical implications for effective long-term restoration efforts are discussed.

Digital elevation models (DEM) are mathematical representations of the Earth's bare surface in computer-readable format. The underlying measurements are often obtained by remote sensing and photogrammetry methods and processed into continuous raster data. Each of these data sources, however, provides imperfect information, and further processing steps often increase the degree of imperfection. Consequently, the process of DEM generation cumulates in uncertainty, which affects subsequent hydro- and geomorphological analyses and modelling (e.g., stream network delineation, flowpath distribution, erosion modelling). In many DEM-based studies, however, the aspect of uncertainty related to the DEM data source has been neglected. Therefore, we propose a new approach for quantifying the effects of DEM uncertainty on hydro-geomorphological modelling based on Gaussian white noise, a concept widely used in signal processing to map noise in signals and extract the actual message context. The basic idea is to add noise to the original DEM values by means of a Gaussian distribution whose parameters are determined from the mean value of the elevation values in a moving window and the device-specific properties (precision and accuracy). We postulate that such an approach can be used to determine uncertainties and their effect on subsequent analysis steps of hydro-geomorphological modelling. It is conceivable to create DEM ensembles depending on known parameters such as the accuracy and precision of the measuring instrument, as is used operationally in weather forecasting. Using such ensembles, probability ranges for terrain and catchment hydro-geomorphological properties can be determined and uncertainty ranges can be specified. Thus, the currently mostly deterministic approach of digital terrain modelling will be replaced by a more probabilistic understanding. Overall, our approach will help decision-makers and scientists to better assess the results of digital terrain analysis. Furthermore, it will also facilitate determining whether a result of DEM-based hydro-geomorphological analysis is sufficiently certain to answer specific research questions.

Over the last few years, the concept of hydrological connectivity has emerged as a useful framework to quantify how changes in water redistribution and sediment production may lead to land degradation. Here, we illustrate the use of the connectivity framework for several examples of dryland systems that are analysed at a variety of spatial and temporal scales using both modelling approaches and remote sensing data analysis. We show that hydrological connectivity is particularly useful in drylands where human and/or natural disturbances can alter the surface water availability and pathways, and therefore the system connectivity. In doing so, we also focus on the analysis of co-evolution of system structures and function, and how they may drive threshold behaviour leading to desertification. We apply the framework to different dryland systems, starting with the analysis of semi-arid rangelands, where feedbacks between the decline in vegetation density and landscape erosion reinforces degradation processes driven by changes in connectivity. We then focus on semi-arid floodplain wetlands, where decreases in water volumes promote terrestrial vegetation encroachment that changes drainage conditions and connectivity, potentially reinforcing redistribution of flow paths to other wetland areas. In both cases, crossing a system threshold might lead to degradation in which the return to a functional system is unlikely. The examples presented highlight the need to incorporate a co-evolutionary framework for the analysis of changing connectivity patterns and the emergence of thresholds in arid and semi-arid systems. This framework can be used for the identification of early warning indicators of transitions from healthy to degraded states, which are useful for management applications.

Runoff and soil erosion in Mediterranean landscapes are affected by multiple factors that interact at a variety of spatial scales with variable degrees of connection. In these systems, connectivity has emerged as a useful concept for exploring the movement of runoff and sediments between landscape locations and across spatial scales. In this study, we examine the structural and functional controls of surface-patch to hillslope-scale runoff and sediment connectivity in three Mediterranean-dry reclaimed mining slope systems that have different long-term development levels of vegetation and rill networks. Structural connectivity, or the extent to which surface patches that facilitate the production of runoff/sediments are physically linked to one another, was assessed using a flowpath analysis of coupled vegetation distribution and surface topography. Functional connectivity, determined as the spatial continuity of surface fluxes across scales, was further explored using the ratio of surface-patch to hillslope-scale observations of runoff and sediment yield for 21 monitored hydrologically active rainfall events. Event-based (functional) runoff connectivity was found to be dynamically controlled by antecedent precipitation conditions and rainfall intensity and, at the same time, was strongly modulated by the structural connectivity of the slopes. In the absence of rill networks, both runoff and sediments for all events were largely redistributed within the analysed systems, resulting in low functional connectivity. Sediment connectivity increased with rainfall intensity, particularly in the presence of rill networks where active incision under high intensity storm conditions led to large non-linear increases in sediment yield from the surface-patch to the hillslope scales. Overall, our results demonstrate the usefulness of applying structural and functional connectivity metrics for practical applications, and for assessing the complex links and controlling factors that regulate the transference of both runoff and sediment yield across different landscape scales.

The Mediterranean basin has been characterized by intense human presence and landscape transformation for centuries. Recent land-use changes point to a general expansion of shrub and forest cover in low-productive mountain areas, especially in the countries on the northern side of the Mediterranean, as a consequence of farmland and grazing abandonment. However, strong urbanization and agriculture intensification are occurring in valleys and coastal areas, particularly on the southern and eastern rims of the basin that are affected by rapid population growth. Extensive revegetation on formerly cultivated land can reduce notably runoff generation and deep water percolation, with important consequences for freshwater supplies. The expansion of irrigated land and urban areas, often accompanied by tourism development, greatly increases water consumption, which may also lead to decline in river discharges and aquifer overexploitation. Projected future decline in the availability of freshwater resources and increased water demand, exacerbated by the present context of changes in climate conditions, make it urgent to establish sustainable land and water management strategies. These require deep understanding of the impact of land-use changes on water resources. Any significant advance in understanding the water cycle requires field observations and measurements accompanied by hydrological modeling approaches that simulate hydrological changes under different land-use and climate scenarios.

In arid and semi-arid ecosystems, shortage of water can trigger changes in landscapes’ structures and function leading to degradation and desertification. Hydrological connectivity is a useful framework for understanding water redistribution and scaling issues associated with runoff and sediment production, since human and/or natural disturbances alter surface water availability and pathways increasing/decreasing connectivity. In this paper, we illustrate the use of the connectivity framework for several examples of dryland systems that are analysed at a variety of spatial and temporal scales. In doing so, we draw particular attention to the analysis of coevolution of system structures and function, and how they may drive threshold behaviour leading to desertification and degradation. We first analyse the case of semi-arid rangelands, where feedbacks between the decline in vegetation density and landscape erosion reinforces degradation processes driven by changes in connectivity until a threshold is crossed above which the return to a functional system is unlikely. We then focus on semi-arid wetlands, where decreases in water volumes promote terrestrial vegetation encroachment that changes drainage conditions and connectivity, potentially reinforcing redistribution of flow paths to other wetland areas. The analysis of dryland wetlands is based on a novel hydrologic connectivity index derived using inundation requirements for wetland vegetation associations. The examples presented highlight the need to incorporate a coevolutionary framework for the analysis of changing connectivity patterns and the emergence of thresholds in arid and semi-arid systems., We acknowledge support from an International Visiting Fellowship from the University of Newcastle awarded to Saskia Keesstra and the COST ActionES1306 (Connecting European Connectivity research). We also acknowledge support from the Australian Research Council through grants FT140100610 and DP140104178. Steven Sandi’s scholarship was partially funded by the Office of Environment and Heritage. Mariano Moreno-de las Heras is beneficiary of a Juan de la Cierva fellowship (IJCI-2015-26463) funded by the Spanish Ministry of Science, Innovation and Universities.

Anthropogenic activities and climate change are imposing an unprecedented pressure on drylands, increasing their vulnerability to desertification. The spatial organization of the sparse vegetation cover is fundamental for the healthy function of the system, and disturbances can trigger cascading feedbacks leading to catastrophic system collapse. Here we discuss some of the latest research aiming at understanding abrupt landscape transitions and possible non-reversible changes, as well as emerging research on the identification of early warning indicators of abrupt transitions to desert states. Robust indicators should take into account temporal system dynamics characteristics, vegetation organization/patch size distribution, functional connectivity measures and human intervention effects.

This study was supported by the research projects MEDhyCON (CGL2012-32446) and EcoHyMed (CGL2013-43418-R) funded by the Spanish Ministry of Economy and Competitiveness (MINECO). Mariano Moreno-de las Heras is beneficiary of a Beatriu de Pinos fellowship (SEDCONMED, 2014 BP-B 00111) co-funded by the Generalitat de Catalunya and the European Commission. Fieldwork and laboratory support by Diego Vuolo and members of the Surface Hydrology and Erosion group (SHEg, IDAEA-CSIC), the Mediterranean Ecogeomorphological and Hydrological Connectivity Research team (MEDhyCON, University of the Balearic Islands) and the Environmental Radioactivity Laboratory (LaboRA, University of the Balearic Islands) are gratefully acknowledged. We also thank the editor, Saskia Keesstra, and four anonymous reviewers for their thoughtful comments.

Este artículo contiene 16 páginas, 6 figuras, 2 tablas., Soil degradation by water is a serious environmental problem worldwide, with specific climatic factors being the major causes. We investigated the relationships between synoptic atmospheric patterns (i.e. weather types, WTs) and runoff, erosion and sediment yield throughout the Mediterranean basin by analyzing a large database of natural rainfall events at 68 research sites in 9 countries. Principal Component Analysis (PCA) was used to identify spatial relationships of the different WTs including three hydro-sedimentary variables: rainfall, runoff, and sediment yield (SY, used to refer to both soil erosion measured at plot scale and sediment yield registered at catchment scale). The results indicated 4 spatial classes of rainfall and runoff: (a) northern sites dependent on North (N) and North West (NW) flows; (b) eastern sites dependent on E and NE flows; (c) southern sites dependent on S and SE flows; and, finally, (d) western sites dependent on W and SW flows. Conversely, three spatial classes are identified for SY characterized by: (a) N and NE flows in northern sites (b) E flows in eastern sites, and (c) Wand SW flows in western sites. Most of the rainfall, runoff and SY occurred during a small number of daily events, and just a few WTs accounted for large percentages of the total. Our results confirm that characterization by WT improves understanding of the general conditions under which runoff and SY occur, and provides useful information for understanding the spatial variability of runoff, and SY throughout the Mediterranean basin. The approach used here could be useful to aid of the design of regional water management and soil conservation measures., This research was supported by projects funded by the MINECOFEDER: CGL2014-52135-C3-3-R, CGL2014-59946-R, CGL2015-65569- R, CGL2015-64284-C2-2-R, and PCIN-2017-061/AEI. When this manuscript was first submitted Estela Nadal-Romero and Damià Vericat received a “Ramón y Cajal” postdoctoral contract (RYC-2013-14371 and RYC‐2010‐06264, Spanish Ministry of Economy and Competitiveness, MEC). Damià Vericat is now a Serra Húnter Fellow at the University of Lleida. María Fernández-Raga received a “José Castillejo” postdoctoral grant (Spanish Ministry of Education, Culture and Sports). Carla Ferreira was supported by a post-doctoral research grant from the Portuguese Science and Technology Foundation (SFRH/ BPD/120093/2016). Mariano Moreno-de las Heras received a Juan de la Cierva postdoctoral contract (IJCI-2015-26463) from the MEC. José Andrés López-Tarazón received a Vicenç Mut postdoctoral fellowship from the Autonomous Balearic Government (CAIB PD/038/2016). José Andrés López-Tarazón and Ramon Batalla also acknowledge 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 (RIUSFluvial Dynamics Research Group), and the CERCA Programme. This paper has benefited from the Lab and Field Data Pool created within the framework of the COST action CONNECTEUR (ES1306).

Badlands are pervasive in a wide range of environmental conditions across the Mediterranean region, including arid, semiarid, and humid environments. On montane (cold subhumid and humid) Mediterranean landscapes, harsh thermal conditions on north-facing hillslopes favour intense bedrock weathering by freezing and impose serious constraints on plant colonization. The above are the customary arguments to explain the high abundance of montane badlands on north-exposed shady aspects. We studied the distribution and morphological diversity of badlands in the upper Llobregat basin (Catalan Pyrenees, NE Spain), using remote sensing information (high-resolution orthophotos and complementary Landsat 8 imagery), digital elevation data, and regional information on lithology. Badlands extend over about 200 ha in the upper Llobregat basin and occur on two different parent materials, swelling (smectite-rich) continental Garumnian lutites of late Cretaceous age, and nonswelling (illitic) marine Eocene marls. Vegetation, assessed by remote-sensed vegetation greenness, is less developed on north-facing badland slopes. However, badland slope-aspect distribution varies considerably with lithology. While badlands on Eocene marls show preferential distribution on north-facing shady slopes, badland occurrence on Garumnian lutites does not reveal clear slope-aspect anisotropy patterns. Lithology also affects slope gradient, with badlands on Eocene marls showing rougher topography (30–40° average slope angle) than on Garumnian lutites (20–30°). Badland morphological differences induced by lithology are discussed in terms of the greater weathering susceptibility and slope instability of the swelling, smectite-rich Garumnian lutites than of the nonswelling Eocene marls. Elevation, which broadly controls annual precipitation and winter air temperature within the region, shows no clear influence on badland distribution. Overall, our results reveal lithology as the main factor controlling badland distribution and morphological diversity under the montane Mediterranean conditions of the upper Llobregat basin. © 2016 Elsevier B.V., This study is supported by a Beatriu de Pinós fellowship (2014 BP-B 00111: SEDCONMED) co-funded by the Generalitat de Catalunya and the European Commission, and a research project (CGL2012-32446: MEDhyCON) funded by the Spanish Ministry of Economy and Competitiveness. We are grateful to the U.S. Geological Survey and the Institut Cartogràfic i Geològic de Catalunya for granting access to the Landsat 8 image, high-resolution orthophotos, digital elevation models and digital geological map that were used in this study. We also thank the reviewers, Milika Kasanin-Grubin and David Regüés, and the Editor, Richard A. Marston, for their thoughtful comments, and Michael Eaude for language corrections.

Digital Terrain Models (DTMs) are currently a fundamental source of information in Earth Sciences. However, DTM-based studies can contain remarkable biases if limitations and inaccuracies of these models are disregarded. In this work, four freely available datasets such as SRTM C-SAR DEM, ASTER GDEM V2 and two airborne LiDAR derived DTMs (at 5 and 1 m spatial resolution, respectively) were analysed in a comparative study in three geomorphologically contrasted catchments located in Mediterranean geoecosystems under intensive human land use influence. Vertical accuracy as well as the influence of each dataset characteristics on hydrological and geomorphological modelling applicability were assessed by using classic geometric and morphometric parameters and the more recently proposed index of sediment connectivity. Overall vertical accuracy – expressed as Root Mean Squared Error (RMSE) and Normalized Median Deviation (NMAD) – revealed the highest accuracy in the cases of the 1 m (RMSE = 1.55 m; NMAD = 0.44 m) and 5 m LiDAR DTMs (RMSE = 1.73 m; NMAD = 0.84 m). Vertical accuracy of SRTM was lower (RMSE = 6.98 m; NMAD = 5.27 m) but considerably higher than in the case of ASTER (RMSE = 16.10 m; NMAD = 11.23 m). All datasets were affected by systematic distortions. As a consequence, propagation of these errors caused negative impacts on flow routing, stream network and catchment delineation and, to a lower extent, on the distribution of slope values. These limitations should be carefully considered when applying DTMs for hydrogeomorphological modelling.

Climate change and the widespread alteration of natural habitats are major drivers of vegetation change in drylands. In the Chihuahuan Desert, large areas of grasslands dominated by perennial grass species have transitioned over the last 150 years to shrublands dominated by woody species, accompanied by accelerated water and wind erosion. Multiple mechanisms drive the shrub-encroachment process, including precipitation variations, land-use change, and soil erosion–vegetation feedbacks. In this study, using a simple ecohydrological modelling framework, we show that herbaceous (grasses and forbs) and shrub vegetation in drylands have different responses to antecedent precipitation due to functional differences in plant-growth and water-use patterns. Therefore, shrub encroachment may be reflected in the analysis of landscape-scale vegetation–rainfall relationships. We analyse the structure and dynamics of vegetation at an 18 km2 grassland–shrubland ecotone in the northern edge of the Chihuahuan Desert (McKenzie Flats, Sevilleta National Wildlife Refuge, NM, USA) by investigating the relationship between decade-scale (2000–2013) records of remotely sensed vegetation greenness (MODIS NDVI) and antecedent rainfall. NDVI–rainfall relationships show a high sensitivity to spatial variations on dominant vegetation types across the grassland–shrubland ecotone, and provide biophysical criteria to (a) classify landscape types as a function of the spatial distribution of dominant vegetation and to (b) decompose the NDVI signal into partial components of annual net primary production (ANPP) for herbaceous vegetation and shrubs. Analysis of remotely sensed ANPP dynamics across the study site indicates that plant growth for herbaceous vegetation is particularly synchronized with monsoonal summer rainfall. For shrubs, ANPP is better explained by winter plus summer precipitation, overlapping the monsoonal period (June–September) of rain concentration. Our results suggest that shrub encroachment was not particularly active in this Chihuahuan ecotone for the period 2000–2013. However, future changes in the amount and temporal pattern of precipitation (i.e. reductions in monsoonal summer rainfall and/or increases in winter precipitation) may enhance the shrub-encroachment process, particularly in the face of expected upcoming increases in aridity for desert grasslands of the southwestern USA.

Soil water-content (SWC) variability in forest ecosystems is affected by complex interactions between climate, topography, forest structure and soil factors. However, detailed studies taking into account the combined effects of these factors are scarce. This study's main aims were to examine the control that throughfall exerts on local spatial variation of near-surface soil water-content and to combine this information with forest structure and soil characteristics, in order to analyze all their effects together. Two stands located in the Vallcebre Research Catchments (NE Spain) were studied: one dominated by Quercus pubescens and the other by Pinus sylvestris. Throughfall and the related shallow SWC were monitored in each plot in 20 selected locations. The main characteristics of the nearest tree and soil parameters were also measured. The results indicated that mean SWC increment at the rainfall event scale showed a strong linear relationship with mean throughfall amount in both forest plots. The % of locations with SWC increments increased in a similar way to throughfall amount in both forest plots. The analyses considering all the effects together indicated again that throughfall had a significant positive effect in both forest plots, while soil litter depth showed a significant negative effect for the oak plot but lower statistical significance for the pine plot, showing a comparable –although more erratic– influence of the organic forest floor for this plot. These results, together with lower responses of SWC to throughfall than expected in rainfall events characterized by low preceding soil water-condition and high rainfall intensity, suggest that litter layer is playing an important role in controlling the soil water-content dynamics. The biometric characteristics of the nearest trees showed significant but very weak relationships with soil water-content increment, suggesting that stemflow and throughfall may act at lower distances from tree trunk than those presented in our study. © 2018 Elsevier B.V., This research was supported by the projects TransHyMed (CGL2016-75957-R AEI/FEDER, UE) and MASCC-DYNAMITE (PCIN-2017-061/AEI) funded by the “Agencia Estatal de Investigación”. A.J. Molina and M. Moreno de las Heras are beneficiaries of Juan de la Cierva post-doctoral fellowships; and C. Cayuela, of an FPI grant, all of them funded by the Spanish Ministry of Economy and Competitiveness. Support provided by A. Löchner, X. Huguet, M. Roig-Planasdemunt, E. Sánchez-Costa, G. Bertran is also acknowledged. The constructive comments of two anonymous reviewers on an earlier version of this manuscript are thanked.

This paper presents the main results obtained from the study of hydrological processes in the Vallcebre Research Catchments since 1988. Distributed hydrometric measurements, environmental tracers and hydrological modelling were used to understand Mediterranean catchment behaviour and to provide new data to help assess the global change effects on these catchments’ water resources. Thirty years of hydrological processes observation in the Vallcebre Research Catchments have increased understanding not only of their hydrological response, but also of the main hydrological and erosion processes characteristic of Mediterranean mountain catchments. This paper briefly summarises the main results obtained since 1988 on ecohydrological processes, hydrological response, runoff generation processes, erosion and sediment transport. Some of the main findings from this research are (i) the importance of temporal variability in precipitation to determine the hydrological processes; (ii) the paramount role played by forest cover in reducing soil water content; (iii) the marked influence of antecedent wetness conditions on runoff generation that determine different runoff responses; (v) the dominant contribution of pre-existing water during floods; (vi) the importance of freezing-thawing processes in badland areas on erosion and the role of summer convective storms in controlling sediment transport. © Universidad de La Rioja., The 30 years of research in the Vallcebre catchments have been carried out with the support of various research projects funded by the Spanish government and the European Community. Among these are the two current projects: TransHyMed (CGL2016-75957-R AEI/FEDER, UE) and MASCC-DYNAMITE (PCIN-2017-061/AEI). Research into the Vallcebre catchments also received funding from the convention between the CSIC and the MAPAMA (RESEL). C. Cayuela is beneficiary of a pre-doctoral FPI grant (BES-2014-070609), A. Molina and M. Moreno de las Heras are beneficiaries of contracts within the “Juan de la Cierva” program (FJCI-2015-24597 and IJCL-2015-26463, respectively), funded by the Spanish Ministry of Economy, Industry and Competitiveness, and G. Bertran is beneficiary of a contract within the program “Sistema Nacional de Garantía Juvenil” (CS2_CAT_ IDAEA_049). The authors are very grateful to all those who have collaborated in the research carried out during these 30 years, and especially to: O. Ávila, X. Huguet, P. García-Estringana, R. Poyatos, D. Regüés, C. Rubio and M. Soler.

Badlands are erosive landforms of highly dissected morphology that are pervasive on soft bedrock in a variety of climate conditions. Although these systems share common geomorphological features, badlands may show diverse erosive activity, age and dynamic behaviour, which complicates the analysis of the reasons for badland initiation. This study's extensive review of badland mechanisms and predisposing factors indicates that badland development is controlled by the incidence of four general terrain instability factors: relief vigour in the form of topographic gradient or active base-level conditions, weatherable and erosion-susceptible soft lithology, an erosive climate and, finally, a disturbance or environmental condition limiting the development of protective vegetation. Local lithology, regional to local tectonics, climate oscillations and the effects of both extreme natural events and human action play a dominant role in determining whether these four instability factors converge in a landscape, ultimately to lead to the initiation, stabilization and rejuvenation of badlands.

The effects of ecosystem degradation are pervasive worldwide and increasingly concerning under the present context of global changes in climate and land use. Theoretical studies and empirical evidence increasingly suggest that drylands are particularly prone to develop nonlinear functional changes in response to climate variations and human disturbance. Precipitation-use efficiency (PUE) represents the ratio of vegetation production to precipitation and provides a tool for evaluating human and climate impacts on landscape functionality. Holm oak (Quercus ilex) woodlands are one of the most conspicuous dry forest ecosystems in the western Mediterranean basin and present a variety of degraded states, due to their long history of human use. We studied the response of Iberian holm oak woodlands to human disturbance along an aridity gradient (that is, semi-arid, dry-transition and sub-humid conditions) using PUE estimations from enhanced vegetation index (EVI) observations of the Moderate-Resolution Imaging Spectroradiometer (MODIS). Our results indicated that PUE decreased linearly with disturbance intensity in sub-humid holm oak woodlands, but showed accelerated, nonlinear reductions with increased disturbance intensity in semi-arid and dry-transition holm oak sites. The impact of disturbance on PUE was larger for dry years than for wet years, and these differences increased with aridity from sub-humid to dry-transition and semi-arid holm oak woodlands. Therefore, aridity may also interact with ecosystem degradation in holm oak woodlands by reducing the landscape ability to buffer large changes in vegetation production caused by climate variability., This study was supported by a project (INDICAR, CGL2013-42213-R) funded by the Spanish Ministry of Economy, Industry and Competitiveness (MEIC). MMdlH research was supported by a Beatriu de Pinós fellowship (2014 BP-B00111) co-funded by the Generalitat de Catalunya and the European Commission, and a Juan de la Cierva fellowship (IJCI-2015-26463) funded by the MEIC. We are grateful to the NASA, IGN and AEMET for granting access to the MODIS EVI data, high-resolution PNOA orthophotos and precipitation records, respectively, that were applied in this study. We also thank two anonymous reviewers and the subject-matter editor, Brandon Bestelmeyer, for their helpful comments, and Jesús Romero for language corrections.

[1] Nonlinear interactions between physical and biological factors give rise to the emergence of remarkable landform‐vegetation patterns. Patterns of vegetation and resource redistribution are linked to productivity and carrying capacity of the land. As a consequence, growing concern over ecosystem resilience to perturbations that could lead to irreversible land degradation imposes a pressing need for understanding the processes, nonlinear interactions, and feedbacks, leading to the coevolution of these patterns. For arid and semiarid regions, causes for concern have increased at a rapid pace during the last few decades due to growing anthropic and climatic pressures that have resulted in the degradation of numerous areas worldwide. This paper aims at improving our understanding of the ecogeomorphic evolution of landscape patterns in semiarid areas with a sparse biomass cover through a modeling approach. A coupled vegetation‐pattern formation and landform evolution model is used to study the coevolution of vegetation and topography over centennial timescales. Results show that self‐organized vegetation patterns strongly depend on feedbacks with coevolving landforms. The resulting patterns depend on the erosion rate and mechanism (dominance of either fluvial or diffusive processes), which are affected by biotic factors. Moreover, results show that ecohydrologic processes leading to banded pattern formation, when coupled with landform processes, can also lead to completely different patterns (stripes of vegetation along drainage lines) that are equally common in semiarid areas. These findings reinforce the importance of analyzing the coevolution of landforms and vegetation to improve our understanding of the patterns and structures found in nature.

Hydrological heterogeneity is recognized as a fundamental ecosystem attribute in drylands controlling the flux of water and energy through landscapes. Therefore, mosaics of runoff and sediment source patches and sinks are frequently identified in these dry environments. There is a remarkable scarcity of studies about hydrological spatial heterogeneity in restored slopes, where ecological succession and overland flow are interacting. We conducted field research to study the hydrological role of patches and slopes along an "overland flow gradient" (gradient of overland flow routing through the slopes caused by different amounts of run-on coming from upslope) in three reclaimed mining slopes of Mediterranean-continental climate. We found that runoff generation and routing in non-rilled slopes showed a pattern of source and sink areas of runoff. Such hydrological microenvironments were associated with seven vegetation patches (characterized by plant community types and cover). Two types of sink patches were identified: shrub Genista scorpius patches could be considered as "deep sinks", while patches where the graminoids Brachypodium retusum and Lolium perenne dominate were classified as "surface sinks" or "runoff splays". A variety of source patches were also identified spanning from "extreme sources" (Medicago sativa patches; equivalent to bare soil) to "poor sources" (areas scattered by dwarf-shrubs of Thymus vulgaris or herbaceous tussocks of Dactylis glomerata). Finally, we identified the volume of overland flow routing along the slope as a major controlling factor of "hydrological diversity" (heterogeneity of hydrological behaviours quantified as Shannon diversity index): when overland flow increases at the slope scale hydrological diversity diminishes.

The management of reclaimed slopes derived from industrial and civil activities (e.g. surface mining and road construction) requires the development of practical stability analysis approaches that integrate the processes and mechanisms that rule the dynamics of these ubiquitous emerging ecosystems. This work describes a new modelling approach focused on stability analysis of water-limited reclaimed slopes, where interactive relationships between rill erosion and vegetation regulate ecosystem stability. Our framework reproduces two main groups of possible trends along the temporal evolution of reclaimed slopes: successful trends, characterized by widespread vegetation development and the effective control of rill erosion processes; and gullying trends, characterized by the progressive loss of vegetation and a sharp logistic increase in erosion rates. Furthermore, this analytical approach allows the determination of threshold values for the state variables (i.e. vegetation cover and rill erosion) that drive the system's stability, facilitating the identification of critical situations that require specific human intervention (e.g. revegetation or, in very problematic cases, revegetation combined with rill network destruction) to ensure the long-term sustainability of the restored ecosystem. The application of our threshold analysis framework in Mediterranean-dry reclaimed slopes derived from surface coal mining (the Teruel coalfield in central-eastern Spain) showed a good field-based performance. Therefore, we believe that this model is a valuable contribution for the management of water-limited reclaimed systems, including those associated with rill erosion, as it provides a tool for the evaluation of restoration success and can play an important role in decision-making during ecosystem restoration in severely disturbed landscapes. Copyright © 2011 John Wiley & Sons, Ltd.

Vegetation, soil, and hydrology in drylands often collectively exhibit strong ecohydrological interrelationships in which vegetation both influences and is influenced by runoff, particularly on sites with more gradual slopes. These two-way relationships have important implications for ecological restoration of disturbed sites, such as those being reclaimed following mining, yet studies from both ecological and hydrological perspectives specifically evaluating how the strength of ecohydrological interrelationships varies for a range of natural and restored conditions are still missing. We assessed two-way relationships between vegetation and soil hydrological properties by evaluating patterns of both plant community structure and soil hydrological characteristics related to runoff for natural sites and restored sites following mining. At the plot scale, we identified eight ecohydrological units based on interrelationships between vegetation communities and hydrological properties associated with runoff along a progression from source to sink patch types. Similarly, at the hillslope scale, which included patches of different types, we found a correspondence between the proportions of source and sink patches and both vegetation community and hydrological properties. The relative strength of ecohydrological interrelationships in hillslope mosaics decreased with decreasing disturbance except for rilled hillslopes, likely because parts of the hillslope become isolated from the others. Our results highlight, in general, how ecohydrological interrelationships are related with degree of disturbance, and in particular, how rilling alters ecohydrological interrelationships, thereby precluding effective restoration.

Soil moisture is considered the main limiting factor governing the structure and dynamics of vegetation in drylands. Soil erosion is perceived as a critical process affecting these systems, especially when rill formation occurs, as rill networks can condition the availability and spatial distribution of soil moisture. To assess the impact of soil erosion processes on the dynamics of Mediterranean-dry reclaimed systems, during the 2005–06 hydrological year we monitored the soil moisture regime (temporal availability and spatial distribution) and the associated responses describing vegetation performance (plant water status and potential seed germination) and vegetation structure in five coal-mining reclaimed slopes subjected to different rill erosion rates (from 0 to about 70 t ha − 1 year − 1 ). Rill network development leads to increased runoff connectivity and to concentration of water flow along the channeling network. As a result, water loss from the slope system is maximized. Simultaneously, the spatial distribution of soil moisture is ruled by the pattern of geomorphic forms (rill and interrill units). The ecological consequences are led by the intensification of water stress and the occurrence of unfavorable conditions for plant recruitment and natural colonization, causing a non-linear decline of species richness and aboveground biomass at the slope scale level. When dense rill networks are developed, long-term effects of erosion result in a sharp ecosystem transition to a very simple and low productive plant community spatially organized in downward spots adjacent to the rills, where plants minimize simultaneously water stress and the mechanical disturbance associated to concentrated flows.

Soil erosion in reclaimed mines may affect plant colonization and performance, and may compromise restoration success; however, the magnitude of this effect has seldom been quantified. We monitored the dynamics of vegetation (seed bank density, seedling emergence, plant mortality, and seed production) during a growing season (2003-2004) in three constructed slopes with differing past erosion rates. The slopes are located in the Utrillas coalfield in Spain, which experiences a Mediterranean-continental climate. In the most eroded slope, soil water availability was lower--especially in the interrill areas--and seedling emergence rate, plant survival, and seed production were also significantly lower than on the less eroded slopes. We found that vegetation recovery is dramatically constrained when rill erosion rate is 17 t ha⁻¹ yr⁻¹ and plant cover is 30%, but this effect disappears when plant cover is higher than 60%. Soil erosion in constructed slopes appears to inhibit natural plant colonization processes by increasing runoff water loss over the long-term. Thus, when rill erosion networks develop, human intervention would be needed to minimize the loss of water and facilitate vegetation colonization.

Vegetation cover plays a major role in the restoration and stabilization of disturbed systems. The analysis of relationships between restored vegetation and soil hydrology has special relevance for the evaluation and operation of mining reclamation, particularly in Mediterranean-Continental environments, where climatic conditions restrict the development of continuous vegetation cover. The effect of herbaceous vegetation cover on soil hydrology was analysed by means of rainfall simulation (63 mm h − 1 ; 0.24 m 2 ) in reclaimed soils derived from opencast coal mining (a non-saline and clay-loam textured spoil) in central-eastern Spain. A total of 75 simulation experiments were conducted at three different times throughout the year (late winter, summer and autumn) to control the influence of seasonal climatic fluctuations. Sediment concentrations in runoff and the runoff coefficient decreased exponentially with vegetation cover, while increases in steady infiltration rates were obtained with vegetation cover. Additional delays in runoff responses (longer time to runoff start and stabilization) and increases in the wetting front depth were observed with vegetation cover. Seasonal variations in soil surface state and moisture strongly influenced hydrological responses; although the influence of season on the analysed hydrological responses was attenuated by vegetation cover, especially in the case of infiltration rates. We also determined a practical ground cover threshold for site restoration and evaluation of over 50% vegetation cover, which could help achieve an optimum biological control of hydrological soil responses in the studied environment.

The main aim of this work was to analyse the development of soil functionality (aggregate development and soil biological functionality) on mining spoils 18 years after reclamation affected by different levels of soil erosion (rill erosion rate from 0 up to 70 t ha− 1 year− 1) in a Mediterranean-Continental environment. For this purpose, different parameters were determined: the size distribution and stability of soil aggregates [mean weight diameter (MWD), microparticles and macroparticles proportions (MIP and MAP), and aggregate stability (AS)]; soil microbial population size [microbial biomass C (MBC)] and activity [basal respiration (BR) and dehydrogenase activity (DHA)]; and soil hydrolase activities [phosphatase (PHA), β-glucosidase (β-GA) and urease (UA)]. Soil ecological trends obtained from Principal Component Analysis revealed the accumulation of organic matter from restored vegetation as the triggering factor for the development of soil aggregation and biological functionality. The spatial differentiation of reclaimed vegetation was the principal source of variability for these soil forming processes, which were also conditioned by the presence of variations on soil particle size distribution. Erosion-related exponential decreases of AS, BR, DHA, PHA, β-GA and UA were identified. In fact, limitations of vegetation development caused by accelerated soil erosion drastically constrained the development and spatial organisation of both physical structure and soil biological functionality, by preventing the accumulation of soil organic matter. Although soil forming processes in uneroded conditions occurred, soil functionality levels were rather low, probably due to the small amounts of soil organic matter reached, generally

Mining reclamation results obtained in the Teruel coalfield (Mediterranean-dry Spain) during the last 30 years have been quite limited. In order to improve restoration operations we conducted a study to analyse the trajectories of ecological succession and identify the main driving forces that control vegetation dynamic in reclaimed artificial slopes. A total of 87 slopes of different ages and restoration treatments were classified and characterized after recording different variables related to topography, restoration techniques, vegetation, local disturbances and soil erosion. Successional trends were inferred from gradient analysis as well as the factors, mechanisms and processes implied. We found a wide variety of plant communities and successional trajectories. Initial conditions (soil quality and revegetation treatments) as well as the environmental scenario (climatic conditions and vicinity of preserved propagule sources) were the main driving forces directing vegetation succession. Soil erosion triggered by external run-on coming from surrounding structures was also identified as a key factor determining the evolution of vegetation in these dry environments. Other local disturbances (grazing and fungal pests) can favour vegetation transition in communities dominated by highly competitive non-native sown species to more diverse shrub communities. Some practical considerations for future reclamation projects are suggested.

Dryland ecosystems are often characterized by patchy vegetation and exposed soil. This structure enhances transport of soil resources and seeds through the landscape (primarily by wind and water, but also by animals), thus emphasizing the importance of connectivity – given its relation to the flow of these materials – as a component of dryland ecosystem function. We argue that, as with the fertile-islands conceptual model before it, the concept of connectivity explains many phenomena observed in drylands. Further, it serves as an organizing principle to understand dryland structure and function at scales from individual plants to entire landscapes. The concept of connectivity also helps to organize thinking about interactions among processes occurring at different scales, such as when processes at one scale are overridden by processes at another. In these cases, we suggest that state change occurs when fine-scale processes fail to adjust to new external conditions through resource use or redistribution at the finer scale. The connectivity framework has practical implications for land management, especially with respect to decision making concerning the scale and location of agricultural production or habitat restoration in the world's drylands.

Semiarid and arid environments are frequently structured in vegetation patches that heterogeneously distribute water resources (water runoff and soil moisture). This redistribution is interrelated with episodes of rainfall triggering pulses of plant growth according to the Trigger–Transfer–Reserve–Pulse (TTRP) model. Spatial heterogeneity in the hydrological behaviour of surface patches has been described in Mediterranean mining restored hillslopes. Nevertheless studies describing the interactions of this hydrological heterogeneity with ecological processes on restored environments are lacking. This study investigates the relationships between overland flow running at hillslope scale and ecosystem processes at patch scale in restored hillslopes. We selected three approximately 20 year old restored hillslopes along a gradient of overland flow (hillslope runoff coefficients are 15.9%, 2.2% and 0.3% for the three experimental hillslopes). We studied environmental conditions describing the ecohydrological interactions under the TTRP approach for arid and semiarid environments. Our results indicate that in restored hillslopes: 1) soil moisture content was associated to the type of vegetation patches; 2) higher soil water content enhanced vegetation diversity and soil properties, improving vegetation performance and colonization opportunities; and 3) there was an inverse relationship between the volume of overland flow and soil moisture at the hillslope scale, influencing, in turn, ecohydrological processes at the patch scale. Overall our results highlight the importance of overland flow modifying soil moisture distribution at patch scale and hence, influencing vegetation dynamics and ecological succession in these novel ecosystems.

Tiscar Espigares,* Luis Merino-Martin, Mariano Moreno-de las Heras and Jose-Manuel Nicolau 1 Department of Ecology, University of Alcala, Alcala de Henares, E-28871, Spain 2 Botanic Gardens and Parks Authority, Kings Park and Botanic Garden, Perth, WA 6005, Australia 3 School of Plant Biology, University of Western Australia, Nedlands, WA 6009, Australia 4 Department of Agriculture and Economy, Polytechnic School, University of Zaragoza, Huesca, E-22071, Spain

[1] Dryland vegetation frequently shows self-organized spatial patterns as mosaic-like structures of sources (bare areas) and sinks (vegetation patches) of water runoff and sediments with variable interconnection. Good examples are banded landscapes displayed by Mulga in semiarid Australia, where the spatial organization of vegetation optimizes the redistribution and use of water (and other scarce resources) at the landscape scale. Disturbances can disrupt the spatial distribution of vegetation causing a substantial loss of water by increasing landscape hydrological connectivity and consequently, affecting ecosystem function (e.g., decreasing the rainfall-use efficiency of the landscape). We analyze (i) connectivity trends obtained from coupled analysis of remotely sensed vegetation patterns and terrain elevations in several Mulga landscapes subjected to different levels of disturbance, and (ii) the rainfall-use efficiency of these landscapes, exploring the relationship between rainfall and remotely sensed Normalized Difference Vegetation Index. Our analyses indicate that small reductions in the fractional cover of vegetation near a particular threshold can cause abrupt changes in ecosystem function, driven by large nonlinear increases in the length of the connected flowpaths. In addition, simulations with simple vegetation-thinning algorithms show that these nonlinear changes are especially sensitive to the type of disturbance, suggesting that the amount of alterations that an ecosystem can absorb and still remain functional largely depends on disturbance type. In fact, selective thinning of the vegetation patches from their edges can cause a higher impact on the landscape hydrological connectivity than spatially random disturbances. These results highlight surface connectivity patterns as practical indicators for monitoring landscape health.

Tree architecture has important consequences for tree performance as it determines resource capture, mechanical stability and dominance over competitors. We analyzed architectural relationships between stem and crown dimensions for 13 dominant Iberian canopy tree species belonging to the Pinaceae (six Pinus species) and Fagaceae (six Quercus species and Fagus sylvatica) and related these architectural traits to wood density, shade tolerance and climatic factors. Fagaceae had, compared with Pinaceae, denser wood, saplings with wider crowns and adults with larger maximal crown size but smaller maximal height. In combination, these traits enhance light acquisition and persistence in shaded environments; thus, contributing to their shade tolerance. Pinaceae species, in contrast, had low-density wood, allocate more resources to the formation of the central trunk rather than to branches and attained taller maximal heights, allowing them to grow rapidly in height and compete for light following disturbances; thus, contributing to their high light requirements. Wood density had a strong relationship with tree architecture, with dense-wooded species having smaller maximum height and wider crowns, probably because of cheaper expansion costs for producing biomechanically stable branches. Species from arid environments had shorter stems and shallower crowns for a given stem diameter, probably to reduce hydraulic path length and assure water transport. Wood density is an important correlate of variation in tree architecture between species and the two dominant families, with potentially large implications for their resource foraging strategies and successional dynamics. © 2012 The Author(s).