Rivaes, R. P., Feio, M. J., Almeida, S. F. P., Vieira, C., Calapez, A. R., Mortágua, A., Gebler, D., Lozanovska, I., Aguiar, F. C. (2020). Multi-biologic group analysis for an ecosystem response to longitudinal river regulation gradients. Science of The Total Environment, 767. DOI: 10.1016/j.scitotenv.2020.144327 Abstract: This work assesses the effects of river regulation on the diversity of different instream and riparian biological communities along a relieve gradient of disturbance in regulated rivers. Two case studies in Portugal were used, with different river regulation typology (downstream of run-of-river and reservoir dams), where regulated and free-flowing river stretches were surveyed for riparian vegetation, macrophytes, bryophytes, macroalgae, diatoms and macroinvertebrates. The assessment of the regulation effects on biological communities was approached by both biological and functional diversity analysis. Results of this investigation endorse river regulation as a major factor differentiating fluvial biological communities through an artificial environmental filtering that governs species assemblages by accentuating species traits related to river regulation tolerance. Communities' response to regulation gradient seem to be similar and insensitive to river regulation typology. Biological communities respond to this regulation gradient with different sensibilities and rates of response, with riparian vegetation and macroinvertebrates being the most responsive to river regulation and its gradient. Richness appears to be the best indicator for general fluvial ecological quality facing river regulation. Nevertheless, there are high correlations between the biological and functional diversity indices of different biological groups, which denotes biological connections indicative of a cascade of effects leading to an indirect influence of river regulation even on non-responsive facets of communities' biological and functional diversities. These results highlight the necessary holistic perspective of the fluvial system when assessing the effects of river regulation and the proposal of restoration measures.
Lozanovska, I., Rivaes, R., Vieira, C., Ferreira, M. T., Aguiar, F. C. (2020). Streamflow regulation effects in the Mediterranean rivers: How far and to what extent are aquatic and riparian communities affected? Science of The Total Environment, 749. doi: 10.1016/j.scitotenv.2020.141616 Abstract: Dam-induced disruption of the natural continuum of rivers has manifold consequences on fluvial ecosystems, but how distinct plant groups and plant adaptive strategies can mediate the regulation effects is largely unexplored. In this work, we focused on how different plant groups (macrophytes, bryophytes, and riparian woody vegetation) respond to hydrological alterations along the river and across the riparian zone downstream of dams. We specifically aimed to determine the degree of regulation [DOR] and distance from dam [DFD], where river regulation no longer significantly affects plant communities in two case studies – a run-of-river dam and a reservoir in Portugal. We collected data on plant species cover in 7 unregulated and 24 regulated sites in June–July 2019. We performed a cluster and ordination analysis to derive guilds using flow-responsive traits and applied linear models to predict guild alterations along the gradient of DOR and DFD. We established three macrophytes, six bryophytes, and five riparian guilds. Our results showed that the vegetation response to regulation was plant group-reliant and guild-specific. Overall, plant responses were expressed by changes in plant cover, and not by guilds' loss. We observed (1) an increase of the guild cover of macrophytes and a decrease in bryophytes cover with increasing regulation gradient and diverse responses for riparian guilds; (2) an encroachment of riparian vegetation guilds into the channel downstream of the storage reservoir and expansion outwards downstream of the run-of-river dam; (3) a higher number of significant alterations for reservoir sites compared with run-of-river sites. Finally, for particular guilds, we determined specific DOR and DFD from which guild covers became significantly indistinct from respective guild cover in unregulated circumstances. Understanding the communities' responses to diverse regulation types and the extent that different plant adaptations may counter regulation effects can be vital for optimizing river restoration projects.
Lozanovska, I., Bejarano, M.D., Martins, M. J., Nilsson, C., Ferreira, M.T., Aguiar, F.C. (2020). Functional diversity of riparian woody vegetation is less affected by river regulation in the Mediterranean than boreal region. Frontiers in Plant Science 11:857. Abstract: River regulation may filter out riparian plants often resulting in reduced functional diversity, i.e., in the range of functions that organisms have in communities and ecosystems. There is, however, little empirical evidence about the magnitude of such reductions in different regions. We investigated the functional diversity patterns of riparian woody vegetation to streamflow regulation in boreal Sweden and Mediterranean Portugal using nine plant functional traits and field data from 109 sampling sites. We evaluated changes in mean plant functional traits as well as in indices of multidimensional functional traits, i.e., functional richness (FRic) and functional redundancy (FRed) within regions and between free-flowing and regulated river reaches. We found that regulation significantly reduced functional diversity in Sweden but not in Portugal. In Sweden, the increased magnitude of variations in water flow and water level in summer, the prolonged duration of extreme hydrological events, the increased frequency of high-water pulses, and the rate of change in water conditions were the likely main drivers of functional diversity change. Small riparian plant species with tiny leaves, poorly lignified stems, and shallow root systems were consistently associated with regulated sites in the boreal region. In Portugal, the similar functional diversity values for free-flowing and regulated rivers likely stem from the smaller streamflow alterations by regulation combined with the species legacy adaptations to the Mediterranean natural hydrological regimes. We conclude that streamflow regulation may reduce the functional diversity of riparian woody vegetation, but the magnitude of these effects will vary depending on the adaptations of the local flora and the patterns of streamflow disturbances. Our study provides insights into functional diversity patterns of riparian woody vegetation affected by regulation in contrasting biomes and encourages further studies of the functional diversity thresholds for maintaining ecosystems.
Tenna Riis, Mary Kelly-Quinn, Francisca C Aguiar, Paraskevi Manolaki, Daniel Bruno, María D Bejarano, Nicola Clerici, María Rosário Fernandes, José C Franco, Neil Pettit, Ana P Portela, Olga Tammeorg, Priit Tammeorg, Patricia M Rodríguez-González, Simon Dufour, Global Overview of Ecosystem Services Provided by Riparian Vegetation, BioScience, biaa041 Abstract: 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.
Fernandes, M.R.; Aguiar, F.C.; Martins, M.J.; Rico, N.; Ferreira, M.T.; Correia, A.C. Carbon Stock Estimations in a Mediterranean Riparian Forest: A Case Study Combining Field Data and UAV Imagery. Forests 2020, 11, 376. Abstract: 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 ± 90 tC ha−1) followed by Alnus glutinosa (L.) Gaertner (162 ± 12 tC ha−1) and by Salix salviifolia Brot. (73 ± 17 tC ha−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.
Publication #2 Rico, N.M.M. 2019. Estimativas de Stock de Carbono em zonas ripárias. Dissertação para a obtenção do Grau de Mestre em Gestão e Conservação de Recursos Naturais, Instituto Superior de Agronomia, Universidade de Lisboa, Lisboa, 42 p. Abstract: Riparian ecosystems have a great potential for long-term carbon storage and sequestration. There is a growing demand on accurate estimations for the Mediterranean region. In this thesis we estimated the carbon (C) stocks of a Mediterranean riparian forest using field data collected in 2018 in the aboveground, understory and organic and mineral soil components. The study area is located in a 3 km-long reach of a Tagus River tributary, Portugal, SW Europe. Allometric biomass models were developed for the Iberian endemic willow (Salix salviifolia) while available equations were applied for black alder (Alnus glutinosa), silver wattle, (Acacia dealbata), narrow-leafed ash (Fraxinus angustifolia), grey willow (Salix atrocinerea) and black poplar (Populus nigra), using Diameter at Breast Height (DBH) and Total Height (H), recorded in 14 circular sampling plots.
The results show that the riparian areas dominated by Acacia dealbata have the highest average total values (trees + litter + soil) of carbon stock (275 Ct/ha), followed by the areas dominated by Alnus glutinosa (134 Ct/ha) and by Salix salviifolia (97 Ct/ha). The tree component presents the largest contributions (76%) to the total carbon reservoir, followed by the leaf component (14%) and the soil component (10%). The results also show a high variability in the average carbon stock values for the tree component and for the litter, these results being related to the density, the size of the vegetation and the succession stage of the different species present in the riparian forest under study. As for the soil component, the results show a reduced variability possibly explained by the morphological characteristics and the high fluvial dynamics found along the entire stream.
This thesis provided the foundations for the assessment of the riparian carbon sequestration in similar Mediterranean riparian forests, a highly relevant Ecosystem Service for the regulation of climate change effects.
Publication #1 Aguiar, F.C.; Fernandes, M.R.; Martins, M.J.; Ferreira, M.T. 2019. Effects of a Large Irrigation Reservoir on Aquatic and Riparian Plants: A History of Survival and Loss. Water, 11, 2379. https://doi.org/10.3390/w11112379 Abstract: 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 ‘old’ 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.