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International audience; The Upper Garonne Basin included the largest glacial system in the Pyrenees during the last glacial cycle. Within the long-term glacial retreat during Termination-1 (T-1), glacier fluctuations left geomorphic evidence in the area. However, the chronology of T-1 glacial oscillations on the northern slope of the Central Pyrenees is still poorly constrained. Here, we introduce new geomorphological observations and a 12-sample dataset of 10Be Cosmic-Ray Exposure (CRE) ages from the Ruda Valley. This U-shaped valley, surrounded by peaks exceeding 2800 m a.s.l., includes a sequence of moraines and polished surfaces that enabled to reconstruct the chronology of the last deglaciation. Following the maximum ice extent, warmer conditions prevailing at ~15-14 ka, during the Bølling-Allerød (B-A) Interstadial, favoured glacial retreat in the Ruda Valley. Within the B-A, glaciers experienced two phases of advance/stillstand with moraine formation at 13.5 and 13.0 ka. During the early YD, glacial retreat exposed the highest surfaces of the Saboredo Cirque (~2300-2350 m) at 12.7 ka. Small glaciers persisted only inside the highest cirques (~2470 m), such as in Sendrosa Cirque, with moraines stabilizing at 12.6 ka. The results of this work present the most complete chronology for Pyrenean glacial oscillations from the B-A to the YD.

Thaumetopoea pityocampa is the most important pine defoliator in the Mediterranean 24 basin. Despite being attacked by a number of natural enemies, populations occur 25 frequently at high density in several areas. 26 2 Egg parasitism was studied in 27 pine and cedar forests in Algeria, in relation to the host 27 density (tents per tree) and the proportion of forest cover in the landscape. 28 3 Egg parasitism varied from 2 to 25%, accounted by two parasitoid species the specialist 29 Baryscapus servadeii and the generalist Ooencyrtus pityocampae. 30 4 Tent density was negatively correlated with parasitism by B. servadeii but not with that of 31 O. pityocampae. Conversely, parasitism by O. pityocampae increased with the proportion 32 of forest and agricultural cover, but not that of B. servadeii. 33 5 Maximum summer temperature showed no correlation with parasitism rates. Still, 34 temperature frequently exceeded 40ºC during the period of adult parasitoid activity. 35 6 The low performance of the egg parasitoids at the southern edge of the host range could 36 be explained by the reduced fecundity of the host, climate effects, and phenological 37 mismatching between the parasitoids and the egg development. These and other factors 38 potentially involved need to be further explored with a long-term study of population 39 dynamics. info:eu-repo/semantics/submittedVersion

Riparian Ecological Infrastructures are networks of natural and semi-natural riparian areas located in human-dominated landscapes, crucial in supporting processes that directly or indirectly benefit humans or enhance social welfare. In this study, we developed a novel multimetric index, termed Habitat Ecological Infrastructure’s Diversity Index (HEIDI), to quantify the potential of Riparian Ecological Infrastructures in supporting biodiversity, and related ecosystem services, in three managed landscapes: Intensive Agriculture, Extensive Agriculture, and Forest Production. Metrics describing the structure, composition, and management of riparian vegetation and associated habitats were used to derive the potential of Riparian Ecological Infrastructures in supporting three distinct biological dispersal groups: short-range dispersers (ants), medium-range dispersers (pollinators), and long-range dispersers (birds, bats, and non-flying small mammals). The composition of floristic resources, assessed by identifying trees and shrubs at the species and genus level, and herbaceous plants at the family level, was used as a proxy to evaluate the potential of Riparian Ecological Infrastructures in promoting seed dispersal and pollination ecosystem services provided by the three biological communities. Our research evidenced that Riparian Ecological Infrastructures located in the Forest Production and Intensive Agriculture landscapes exhibited the highest and lowest potential for biodiversity-related ecosystem services, respectively. The Forest Production landscape revealed higher suitability of forage resources for short- and medium-range dispersers and a higher landscape coverage by Riparian Ecological Infrastructures, resulting in more potential to create ecological corridors and to provide ecosystem services. The Riparian Ecological Infrastructures located in the Extensive Agriculture landscape seemed to be particularly relevant for supporting long-ranges dispersers, despite providing less habitat for the biological communities. Land-use systems in the proximity of Riparian Ecological Infrastructures should be sustainably managed to promote riparian vegetation composition and structural quality, as well as the riparian width, safeguarding biodiversity, and the sustainable provision of biodiversity-related ecosystem services info:eu-repo/semantics/publishedVersion

The connectivity of riparian forests can be used as a proxy for the capacity of riparian zones to provide ecological functions, goods and services. In this study, we aim to test the potential of the freely available Copernicus “Riparian Zones” dataset to characterize the connectivity of riparian forests located in two European bioclimatic regions—the Mediterranean and the Central Baltic hydroregions—when subject to a gradient of human disturbance characterized by land-use/landcover and hydromorphological pressures. We extracted riparian patches using the Copernicus “Actual Riparian Zone” (ARZ) layer and calculated connectivity using the Integral Index of Connectivity (IIC). We then compared the results with a “Manual Riparian Zone” (MRZ) layer, produced by manually digitizing riparian vegetation patches over a very high-resolution World Imagery layer. Our research evidenced reduced forest connectivity in both hydroregions, with the exception of Least Disturbed sites in the Central Baltic hydroregion. The ARZ layer exhibited overall suitability to assess the connectivity of riparian forests in the Central Baltic hydroregion, while the Mediterranean hydroregion displayed a consistent pattern of connectivity overestimation in all levels of human disturbance. To address this, we recommend some improvements in the spatial resolution and thematic accuracy of the Copernicus ARZ layer info:eu-repo/semantics/publishedVersion

Ecological infrastructures (EIs) are considered relevant components in agricultural landscapes to support biodiversity and ecosystem services. We used the predatory attacks on lepidopteran dummies as a proxy to assess predation rates in the agricultural matrix and different EIs types according to their location and vegetation structure. We aimed at comparing the effect of different types of EI on the predation intensity in two intensively irrigated agricultural areas located in the Sorraia and Tagus river valleys in central Portugal. We hypothesized that: (1) the predation rate would be higher near EIs compared with the agricultural matrix, (2) the positive effect of EIs on predation rate would differ with their typologies, and (3) the EIs’ proximity and proportion in the surrounding landscape would have a positive effect on the predation rate in agricultural fields. The EI typologies influenced differently the predator groups and the overall predation rate. Major differences were observed for bird predation, being higher in woody EIs. A positive correlation between predation rate and EIs area of the surrounding landscape, as well as a negative correlation with the distance to the nearest riparian and woody EIs, was observed for birds. The observed dissimilarities in the predators’ response may be related to habitat differences and its functional connectivity. The overall monthly low predation rates are possibly related to the intensive agricultural system and the small area occupied by EIs.

Fluvial riparian vegetation (RV) links fluvial and terrestrial ecosystems. It is under significant pressure from anthropogenic activities, and, therefore, the management and restoration of RV are increasingly important worldwide. RV has been investigated from different perspectives, so knowledge on its structure and function is widely distributed. An important step forward is to convert existing knowledge into an overview easily accessible—for example, for use in decision-making and management. We aim to provide an overview of ecosystem services provided by RV by adopting a structured approach to identify the ecosystem services, describe their characteristics, and rank the importance of each service. We evaluate each service within four main riparian vegetation types adopting a global perspective to derive a broad concept. Subsequently, we introduce a guided framework for use in RV management based on our structured approach. We also identify knowledge gaps and evaluate the opportunities an ecosystem service approach offers to RV management.

Riverine landscapes provide numerous ecosystem services, of which pollination is essential to increase the yield, quality, and stability of crops and the biodiversity of wild flora. Pollinators’ behaviour and their community dynamics are often affected by the spatial distribution of floral and nesting resources at the landscape scale, and are thus sensitive to land-use land-cover (LULC) changes and management practices. The main objective of this study is to understand how changes in riparian vegetation and LULC at River Minho affect pollination services. For this, an approach based on the temporal analysis of historical cartography (1898) and current satellite imagery (2016) was used. We developed a novel Pollination Suitability Index for Riverine Landscapes (PSIRL) using LULC data as a proxy of habitat suitability for insect pollinators. PSIRL scores were derived from expert judgment of the local habitat conditions, floral diversity and field surveys. The PSIRL values obtained for both periods were compared using pairwise T-tests. We detected an overall reduction of the pollination services in the riverine landscape of River Minho from 1898 to 2016. However, at local level we observed gains and losses of pollination suitability as a result of distinct LULC changes. There was a marked decrease in the PSIRL in the most downstream and upstream riverine sections due to generalized conversion of scrublands, broadleaved-forests and heterogeneous agricultural areas to artificial surfaces and managed forests dominated by maritime pine and eucalyptus. However, in the middle section of the river, the area occupied by scrublands, riparian and broadleaved forests increased, resulting in an increase of the foraging resources for insects, and a consequent increase of the PSIRL. This index can be used to monitor and capture changes in the pollination suitability of complex riverine landscapes and support further land and river management decisions. The historical cartography proved to be a valuable source of information to characterize LULC change and hence to assess the evolutionary trajectory of pollination ecosystem services, at global and local level.

Present and past permafrost distribution in the Pyrenees is still under discussion. As in other mid-latitude mountain regions, rock glaciers and protalus lobes are the main indicators of permafrost conditions. In this paper we examine the distribution of these landforms in Aran and Boi valleys, formerly glaciated U-shaped valleys ranging from 600 to 3000 m in the southern and northern sides of the Central Pyrenees, respectively. The spatial distribution of these landforms and their chronostratigraphic position within the valley allow a better understanding of the climatic and environmental conditions necessary for their development. Up to 151 permafrost-related landforms were identified in the Boi valley, including 56 rock glaciers and 95 protalus lobes. In the case of the northern Aran valley, 76 rock glaciers and 89 protalus lobes were cataloged corresponding to 165 landforms. Most of the landforms (93% for rock glaciers and 95% for protalus lobes) are located inside the glacial cirques, with a few distributed in the slopes of the formerly glaciated valleys. The lowest elevation of rock glaciers is situated at 1744 m (Aran) and 2007 m (Boi), whereas the lowest protalus lobes are located at 1740 m and 2033 m, respectively. Therefore, this altitude may be indicative of the lowest level recording permafrost conditions during the period in which these landforms formed, with paleotemperatures ca. 7-8 °C lower than present-day. Between 60 and 70% of the protalus lobes and rock glaciers are located between 2300 and 2600 m in Boi valley and 2100 and 2400 m in Aran valley. The aspect shows a prevailing orientation of NW, N and NE for both cases of rock glaciers and protalus lobes, being almost absent in the S, SE and SW aspects. The average slope of both landforms lies between 11 and 27°, with a maximum of 35° for rock glaciers and 29° for protalus lobes. The amplitude/length ratio reveals that rock glaciers placed at lower altitudes are more elongated. The chronostratigraphic position of these landforms within the valley and with respect to the moraine complexes suggests the existence of three generations of permafrost-related landforms which are associated to the massive deglaciation process between the maximum glacial advance of the Last Glaciation and the Holocene.

International audience; The Central Pyrenees hosted a large ice cap during the Late Pleistocene. The cirques under relatively low-altitude peaks (2200–2800 m) include the greatest variety of glacial landforms (moraines, fossil debris-covered glaciers and rock glaciers), but their age and formation process are poorly known. Here, we focus on the headwaters of the Garonne River, namely on the low-altitude Bacivèr Cirque (highest peaks at ~2600 m), with widespread erosive and depositional glacial and periglacial landforms. We reconstruct the pattern of deglaciation from geomorphological observations and a 17-sample dataset of 10Be Cosmic-Ray Exposure (CRE) ages. Ice thickness in the Bacivèr Cirque must have reached ~200 m during the maximum ice extent of the last glacial cycle, when it flowed down towards the Garonne paleoglacier. However, by ~15 ka, during the Bølling-Allerød (B-A) Interstadial, the mouth of the cirque was deglaciated as the tributary glacier shrank and disconnected from the Garonne paleoglacier. Glacial retreat was rapid, and the whole cirque was likely to have been deglaciated in only a few centuries, while paraglacial processes accelerated, leading to the transformation of debris-free glaciers into debris-covered and rock glaciers in their final stages. Climate conditions prevailing at the transition between the B-A and the Younger Dryas (YD) favored glacial growth and the likely development of small moraines within the slopes of the cirque walls by ~12.9 ka, but the dating uncertainties make it impossible to state whether these moraines formed during the B-A or the YD. The melting of these glaciers favored paraglacial dynamics, which promoted the development of rock glaciers as well as debris-covered glaciers. These remained active throughout the Early Holocene until at least ~7 ka. Since then, the landscape of the Bacivèr Cirque has seen a period of relative stability. A similar chronological sequence of deglaciation has been also detected in other cirques of the Pyrenees below 3000 m. As in other mid-latitude mountain regions, the B-A triggered the complete deglaciation of the Garonne paleoglacier and promoted the development of the wide variety of glacial and periglacial landforms existing in the Bacivèr cirque.

Climate change will induce alterations in the hydrological and landscape patterns with effects on riparian ecotones. In this study we assess the combined effect of an extreme climate and land-use change scenario on riparian woody structure and how this will translate into a future risk of riparian functionality loss. The study was conducted in the Tâmega catchment of the Douro basin. Boosted Regression Trees (BRTs) were used to model two riparian landscape indicators related with the degree of connectivity (Mean Width) and complexity (Area Weighted Mean Patch Fractal Dimension). Riparian data were extracted by planimetric analysis of high spatial-resolution Word Imagery Layer (ESRI). Hydrological, climatic and land-use variables were obtained from available datasets and generated with process-based modeling using current climate data (2008-2014), while also considering the high-end RCP8.5 climate-change and "Icarus" socio-economic scenarios for the 2046-2065 time slice. Our results show that hydrological and land-use changes strongly influence future projections of riparian connectivity and complexity, albeit to diverse degrees and with differing effects. A harsh reduction in average flows may impair riparian zones while an increase in extreme rain events may benefit connectivity by promoting hydrologic dynamics with the surrounding floodplains. The expected increase in broad-leaved woodlands and mixed forests may enhance the riparian galleries by reducing the agricultural pressure on the area in the vicinity of the river. According to our results, 63% of river segments in the Tâmega basin exhibited a moderate risk of functionality loss, 16% a high risk, and 21% no risk. Weaknesses and strengths of the method are highlighted and results are discussed based on a resilience perspective with regard to riparian ecosystems.

Dams strongly impair the fluvial environment by altering downstream flows. We analysed riverscapes downstream of three dams and hypothesized that different dam types in rivers with diverse history of land-use and land cover (LULC) change have significant riparian cover differences at diverse biogeomorphic units (banks, riverbanks, islands). We performed a temporal comparison using pre-dam (1965) and post-dam (2013) high-resolution airborne imagery. A new approach was devised to correct the spatial offset between historical and contemporary imagery. Riparian vegetation and LULC (200 m-buffer) were mapped in three rivers of Portugal regulated by the dams Touvedo (run-of-river), Vilarinho das Furnas and Fronhas (storage reservoirs). Five landscape metrics, measures of shape complexity, area and edge effect of riparian patches were computed, including the Weighted Class Area, a metric developed to better interpret the landscape variation. Our findings provide support for the hypothesis of highly altered riverscapes in the post-dam period. For all case studies riparian patches are presently larger, but with less complex shapes and smaller edges. In the present study riparian patches encroach into the river channel, occupy more area and are larger at the two reservoir rivers than at the run-of-river setting. Riparian growth trajectory at the latter is mainly outwards from the active channel and non-vegetated areas in riverbanks and banks are significantly larger; likely due to the washing flows. Redundancy analyses indicated that riparian change was driven by both LULC (agricultural land abandonment and unmanaged forests) and hydrological alterations that jointly determine the structure and spatial trajectories of riparian expansion.

Large rivers on the Iberian Peninsula reflect a long-history of human interventions and natural disturbances in the fluvial corridors and on the surrounding valleys. In this study we aim to characterize the river morphology in pre-regulation times and understand the morphological changes of the large river Tagus (Central Portugal), across space and time. For this, we used comparable military thematic maps from three dates (1855, 1940 and 2000) and evaluated the river landforms, including sinuosity, aquatic, geomorphic and riparian aspects, in three geomorphological zones (Upland, Middle, and Lowland) using a Geographic Information System (GIS). We related the landform variations to the hydrological alterations and to Land-use Land-Cover (hereinafter LULC) changes at valley level. Hydrological data were achieved by simulating river flow regime using the Soil and Water Assessment Tool (SWAT) model. LULC data was obtained by on-screen digitizing of the military thematic maps complemented with ancillary bibliographic information. Metrics for channel form, aquatic and riparian features were quantified in 51 sampling units of 2500 m-long river sections for each period to describe the river morphology. Shannon-Wiener Index (H’) was applied as a descriptor of the morphological diversity. Data analysis revealed a narrowing of the main channel, an overall reduction of the sinuosity, a smaller number of instream geomorphic units and abandoned lateral channels on the most recent period. Morphological alterations were driven primarily by the reduction of floods and sediment inputs, caused by streamflow regulation, while the agricultural intensification, the augment of forest plantations and the reduction of the Mediterranean scrublands induced changes in sediment dynamics and altered the riparian connectivity. The Upland zone showed the highest morphological alterations switching from a historical high-energy section to a low-dynamic zone. We also observed a high morphological variability in the Middle course exhibiting multifaceted gradients of change, while the Lowland zone reflected continuous but less pronounced modifications. River management planning should express the insights of how past and present human alterations affect morphological processes in river-floodplain systems, particularly taking into account river zones’ specificities and how they may react or constrain potential restoration processes.

This study aims to estimate the total biomass aboveground and soil carbon stocks in a Mediterranean riparian forest and identify the contribution of the different species and ecosystem compartments to the overall riparian carbon reservoir. We used a combined field and object-based image analysis (OBIA) approach, based on unmanned aerial vehicle (UAV) multispectral imagery, to assess C stock of three dominant riparian species. A linear discriminator was designed, based on a set of spectral variables previously selected in an optimal way, permitting the classification of the species corresponding to every object in the study area. This made it possible to estimate the area occupied by each species and its contribution to the tree aboveground biomass (AGB). Three uncertainty levels were considered, related to the trade-off between the number of unclassified and misclassified objects, leading to an error control associated with the estimated tree AGB. We found that riparian woodlands dominated by Acacia dealbata Link showed the highest average carbon stock per unit area (251 &plusmn, 90 tC ha&minus, 1) followed by Alnus glutinosa (L.) Gaertner (162 &plusmn, 12 tC ha&minus, 1) and by Salix salviifolia Brot. (73 &plusmn, 17 tC ha&minus, 1), which are mainly related to the stem density, vegetation development and successional stage of the different stands. The woody tree compartment showed the highest inputs (79%), followed by the understory vegetation (12%) and lastly by the soil mineral layer (9%). Spectral vegetation indices developed to suppress saturation effects were consistently selected as important variables for species classification. The total tree AGB in the study area varies from 734 to 1053 tC according to the distinct levels of uncertainty. This study provided the foundations for the assessment of the riparian carbon sequestration and the economic value of the carbon stocks provided by similar Mediterranean riparian forests, a highly relevant ecosystem service for the regulation of climate change effects.

Dammed rivers have unnatural stream flows, disrupted sediment dynamics, and rearranged geomorphologic settings. Consequently, fluvial biota experiences disturbed functioning in the novel ecosystems. The case study is the large irrigation reservoir Alqueva in Guadiana River, Southern Iberia. The study area was divided into three zones: upstream and downstream of the dam and reservoir. For each zone, species composition and land use and land cover (LULC) were compared before and after the Alqueva Dam implementation. Data consist of aquatic and riparian flora composition obtained from 46 surveys and the area (%) of 12 classes of LULC obtained in 90 riverine sampling units through the analysis of historical and contemporary imagery. There was an overall decrease of several endemic species and on the riparian shrublands and aquatic stands, although differences in the proportion of functional groups were not significant. Nevertheless, compositional diversity shows a significant decline in the upstream zone while landscape diversity shows an accentuated reduction in the reservoir area and downstream of the dam, which is likely related to the loss of the rocky habitats of the &lsquo, old&rsquo, Guadiana River and the homogenization of the riverscape due to the irrigation intensification. The mitigation of these critical changes should be site-specific and should rely on the knowledge of the interactions between surrounding lands, ecological, biogeomorphologic, and hydrological components of the fluvial ecosystems.

Rivers are among the most sensitive of all ecosystems to the effects of global change, but options to prevent, mitigate or restore ecosystem damage are still inadequately understood. Riparian buffers are widely advocated as a cost-effective option to manage impacts, but empirical evidence is yet to identify ideal riparian features (e.g. width, length and density) which enhance ecological integrity and protect ecosystem services in the face of catchment-scale stressors. Here, we use an extensive literature review to synthesise evidence on riparian buffer and catchment management effects on instream environmental conditions (e.g. nutrients, fine sediments, organic matter), river organisms and ecosystem functions. We offer a conceptual model of the mechanisms through which catchment or riparian management might impact streams either positively or negatively. The model distinguishes scale-independent benefits (shade, thermal damping, organic matter and large wood inputs) that arise from riparian buffer management at any scale from scale-dependent benefits (nutrient or fine sediment retention) that reflect stressor conditions at broader (sub-catchment to catchment) scales. The latter require concerted management efforts over equally large domains of scale (e.g. riparian buffers combined with nutrient restrictions). The evidence of the relationships between riparian configuration (width, length, zonation, density) and scale-independent benefits is consistent, suggesting a high certainty of the effects. In contrast, scale-dependent effects as well as the biological responses to riparian management are more uncertain, suggesting that ongoing diffuse pollution (nutrients, sediments), but also sources of variability (e.g. hydrology, climate) at broader scales may interfere with the effects of local riparian management. Without concerted management across relevant scales, full biological recovery of damaged lotic ecosystems is unlikely. There is, nevertheless, sufficient evidence that the benefits of riparian buffers outweigh potential adverse effects, in particular if located in the upstream part of the stream network. This supports the use of riparian restoration as a no-regrets management option to improve and sustain lotic ecosystem functioning and biodiversity.

The maximum glacial extent in the Central Pyrenees during the Last Glaciation is known to have occurred before the global Last Glacial Maximum, but the succession of cold events afterwards and their impact on the landscape are still relatively unknown. This study focuses on the environmental evolution in the upper valley of the Garonne River since the Last Glaciation. Geomorphological mapping allows analysis of the spatial distribution of inherited and current processes and landforms in the study area. The distribution of glacial records (moraines, till, erratic boulders, glacial thresholds) suggests the existence of four glacial stages, from the maximum expansion to the end of the glaciation. GIS modeling allows quantification of the Equilibrium Line Altitude, extent, thickness and volume of ice in each glacial stage. During the first stage, the Garonne glacier reached 460 m in the Loures-Barousse-Barbazan basin, where it formed a piedmont glacier 88 km from the head and extended over 960 km 2 . At a second stage of glacier stabilization during the deglaciation process, the valley glaciers were 12–23 km from the head until elevations of 1000–1850 m, covering an area of 157 km 2 . Glaciers during stage three remained isolated in the upper parts of the valley, at heights of 2050–2200 m and 2.6–4.5 km from the head, with a glacial surface of 16 km 2 . In stage four, cirque glaciers were formed between 2260 m and 2590 m, with a length of 0.4–2 km and a glacial area of 5.7 km 2 . Also, the wide range of periglacial, slope, nival and alluvial landforms existing in the formerly glaciated environments allows reconstruction of the post-glacial environmental dynamics in the upper Garonne basin. Today, the highest lands are organized following three elevation belts: subnival (1500–1900 m), nival (1900–2300 m) and periglacial/cryonival (2300–2800 m).

The giant reed ( Arundo donax L.) is amongst the one hundred worst invasive alien species of the world, and it is responsible for biodiversity loss and failure of ecosystem functions in riparian habitats. In this work, field spectroradiometry was used to assess the spectral separability of the giant reed from the adjacent vegetation and from the common reed, a native similar species. The study was conducted at different phenological periods and also for the giant reed stands regenerated after mechanical cutting (giant reed_RAC). A hierarchical procedure using Kruskal–Wallis test followed by Classification and Regression Trees (CART) was used to select the minimum number of optimal bands that discriminate the giant reed from the adjacent vegetation. A new approach was used to identify sets of wavelengths – wavezones – that maximize the spectral separability beyond the minimum number of optimal bands. Jeffries Matusita and Bhattacharya distance were used to evaluate the spectral separability using the minimum optimal bands and in three simulated satellite images, namely Landsat, IKONOS and SPOT. Giant reed was spectrally separable from the adjacent vegetation, both at the vegetative and the senescent period, exception made to the common reed at the vegetative period. The red edge region was repeatedly selected, although the visible region was also important to separate the giant reed from the herbaceous vegetation and the mid infrared region to the discrimination from the woody vegetation. The highest separability was obtained for the giant reed_RAC stands, due to its highly homogeneous, dense and dark-green stands. Results are discussed by relating the phenological, morphological and structural features of the giant reed stands and the adjacent vegetation with their optical traits. Weaknesses and strengths of the giant reed spectral discrimination are highlighted and implications of imagery selection for mapping purposes are argued based on present results.

Spectral discrimination between riparian forests is a challenging issue due to the inherent complexity of species composition and the high spatial structural variability of these vegetation types. This study aimed to evaluate spectral separability among riparian forests, in small and medium-sized river catchment areas, in three bioclimatic zones of Portugal (temperate, transitional, and Mediterranean). We also assess the spectral differences using only the dominant riparian woody species in each riparian forest class, namely Alnus glutinosa, Salix salviifolia, and Nerium oleander. Pixel values were extracted from high-resolution airborne multispectral imagery (red, green, blue, and near-infrared, 50 cm pixels) of 26 riparian forests located in the three bioclimatic zones. Spectral separability was calculated using the transformed divergence (TD) distance. Discriminant analysis (DA) was used to select the bands that contribute most to the spectral separability and for the classification accuracy assessment...