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The current focus of river restoration on flow and sediment transfer without proper consideration of vegetation as a key structuring agent, beyond its stabilising effect, is too simplistic. We contend that vegetation has an essential role in shaping the physical fluvial environment and should be considered equally alongside hydrogeomorphic processes in restoration projects. In support, we introduce engineer plants as important controls, along with flowing water and transported sediments, on the morphodynamics of river systems and associated physical habitat development. The effect of vegetation on channel planform is then summarised, the influence of vegetation on hydrogeomorphic connectivity is outlined, and then the role of vegetation in landform development and habitat provision, as encapsulated in the fluvial biogeomorphic succession model, is described. We then present examples demonstrating how vegetation has contributed to the recovery of degraded rivers through biogeomorphic processes. Finally, we advance the concept of biogeomorphic river restoration by proposing principles to support a closer synthesis of the component sciences and list key areas for practitioners to focus on. Vegetation succession has a significance that goes beyond its physical structure or influence on sediment stability. In many river settings, it is central to channel evolution. The coupled assembly of plant communities and fluvial landforms affect the development of spatially and temporally dynamic habitat through biogeomorphic interactions. Restoration approaches that do not fully consider this dynamic may fail to anticipate river behaviour and recovery trajectories. [ABSTRACT FROM AUTHOR]

An accumulated rainfall of around 100 mm favoured the productivity of the specialist Moustached Warbler Acrocephalus melanopogon, but temperature had a negative effect. By contrast, temperature had a positive effect on the productivity of the generalist Reed Warbler Acrocephalus scirpaceus, whereas rainfall had almost no effect, although productivity also peaked when rainfall approached 100 mm. Understanding the extent to which climate and geography are driving the negative trend of Moustached Warbler productivity, and the stable trend of Reed Warbler productivity. Using data from a breeding bird monitoring ringing scheme in Spain (PASER; 1995 – 2021), we investigated the effects of seasonal rainfall and temperature patterns on the productivity of two sympatric warblers: the resident/short-distance migrant Moustached Warbler (occurring at nine ringing stations from a total of 129), and the generalist long-distance migrant Reed Warbler (57 out of 129 ringing stations). Analyses were performed using multi-adaptive regression splines (MARS). Between 1995 and 2021 geographical and site-specific factors drove annual productivity for both species, combined with rainfall and temperature. For the Moustached Warbler, geographical and site-related variables, together with the temporal changes (year), were more important than rainfall and temperature. For the Reed Warbler, temperature was more important than year but less than site and longitude. Warmer temperatures and a higher frequency of torrential rainfall events may compromise the conservation of the vulnerable Moustached Warbler in Spain due to the adverse effect on productivity. In contrast, increasing temperatures across Spain may benefit the widely distributed Reed Warbler. Thus, Moustached Warbler populations are likely to decrease, whereas Reed Warbler populations might increase. However, further research is needed to establish the impact of climate change on survival, and its implications for the population trends and dynamics of these two sympatric warblers. [ABSTRACT FROM AUTHOR]

Riparian zones are the paragon of transitional ecosystems, providing critical habitat and ecosystem services that are especially threatened by global change. Following consultation with experts, 10 key challenges were identified to be addressed for riparian vegetation science and management improvement: (1) Create a distinct scientific community by establishing stronger bridges between disciplines; (2) Make riparian vegetation more visible and appreciated in society and policies; (3) Improve knowledge regarding biodiversity—ecosystem functioning links; (4) Manage spatial scale and context‐based issues; (5) Improve knowledge on social dimensions of riparian vegetation; (6) Anticipate responses to emergent issues and future trajectories; (7) Enhance tools to quantify and prioritize ecosystem services; (8) Improve numerical modeling and simulation tools; (9) Calibrate methods and increase data availability for better indicators and monitoring practices and transferability; and (10) Undertake scientific validation of best management practices. These challenges are discussed and critiqued here, to guide future research into riparian vegetation. This article is categorized under:Water and Life > Nature of Freshwater EcosystemsWater and Life > Stresses and Pressures on EcosystemsWater and Life > Conservation, Management, and Awareness [ABSTRACT FROM AUTHOR]

Plant communities and dynamics can be characterized according to species composition or plant traits. Here, we used species composition and plant traits to compare their effectiveness in discriminating the biogeomorphological (involving reciprocal feedbacks between physical and biological processes) and ecological (mainly biologically driven) phases of the fluvial biogeomorphological succession (FBS) model. The comparison was done between two French rivers, the largely unchannelized lower Allier and the channelized middle Garonne. One reach representative of each river section was selected for the study. Within each river reach, we chose two contrasted study sites in terms of channel and floodplain dynamics: a reference site (least altered channel and floodplain dynamics) and an altered site (laterally stabilized by riprap and constrained). In the four study sites, we sampled vegetation in 402 plots of 4 m2. The 512 species identified in the plots were characterized in terms of plant traits (20) from a literature review. When comparing reaches in unconstrained ordinations and permutational multivariate analyses of variance, both species composition and plant traits led to a similar identification of the biogeomorphological and the ecological successional trajectories. Nevertheless, the trait approach was less influenced by local and regional bioclimatic, hydrogeomorphological, and anthropogenic settings and thus produced a more comprehensive and general classification of the biogeomorphological and ecological phases of the FBS model. A lower than expected contrast between the four sites was found, because neither species composition nor plant traits could entirely characterize distinct successional trajectories occurring in our reference or altered sites. Furthermore, our results contributed to a better understanding of the multiple successional trajectories that can occur in midlatitude river corridors. It also showed that relating plant traits to their effects on fluvial landform dynamics remains a core challenge in explaining succession including feedback mechanisms between hydrology, morphodynamics, and vegetation dynamics. [ABSTRACT FROM AUTHOR]

Populations of the riparian pioneer species Populus nigra L. which establish on alluvial bars within river channels modulate sediment dynamics and fluvial landforms. Dense cohorts of P. nigra have colonized gravel point bars along the channelized River Garonne, France, during the last 20 years and have enhanced the vertical, lateral and longitudinal development of the bars. For this period, the geomorphic characteristics of two wooded point bars on this laterally stable river are closely linked to the spatial distribution and intensity of establishment and resistance of different cohorts of P. nigra. Furthermore, P. nigra colonization dynamics were controlled by engineer effects of this same species. This relationship is illustrated by a significant correlation between key geomorphic and biological variables measured in situ and characterized with a set of four aerial photographs taken between 2000 and 2010. The development of wooded point bars, which are discrete biogeomorphic units, over the studied period, appear to result from a specific biogeomorphic positive feedback of matter aggregation and vegetation establishment related to sediment trapping and stabilization by pioneer engineer plants. We propose a conceptual model of biogeomorphic unit construction for channelized, lateral stable rivers. We consider the resultant biogeomorphic units as functional from an ecological point of view because P. nigra enhances at the cohort scale (i) its own inherent capacity to resist hydrogeomorphic disturbances, and (ii) its resilience capacity as a result of successful colonization, especially downstream of mature poplar stands. [ABSTRACT FROM AUTHOR]

Abstract European willows (Salicaceae) are pioneer species in temperate zone floodplains. The species are considered invasive and introduction can lead to substantial alteration of floodplain vegetation communities and ecosystem functioning. Invasive spread of different Salicaceae have been attributed to differences in flood tolerance, growth and dispersal between it and co-occurring native species, suggesting a comparative approach examining key traits to be a profitable strategy in elucidating and predicting patterns of Salicaceae invasion. Here we study incipient Salix fragilis invasions in Chilean Patagonia on the western slopes of the Andes. Our approach combines vegetation transect data with dendroecological analysis to compare patterns of niche position along the hydrogeomorphic gradient, niche breadth, and growth rate among S. fragilis and co-occurring species. We evaluated these traits because they are thought to be key to species' capacity to colonize, survive, grow and reproduce in dynamic floodplain habitats. Transect data showed that relative to the most common native trees and shrubs, S. fragilis has the broadest environmental tolerance along the hydrogeomorphic gradient and has a mean niche position closest to severely disturbed and highly flooded channel margins. Moreover, growth models showed that S. fragilis grows faster relative to native species, especially at juvenile stages. Our data suggest that a unique set of trait values allows S. fragilis to occupy a previously under-occupied and abundantly distributed niche, and will continue to colonize, survive, grow and reproduce in morphodynamically disturbed river margins. This is the first report of invasive S. fragilis in Chile, and we comment on potential impacts to native vegetation communities, soil development and ecosystem function. Highlights • Salix fragilis invasion at Chilean Patagonian rivers is reported for the first time. • Salix fragilis grows faster than native riparian species, mainly at juvenile stages. • Compared species' niche breadth and position differ at the hydrogeomorphic gradient. • Unique trait values allow Salix fragilis to occupy a vacant niche along those rivers. • Salix fragilis may alter ecosystem functioning of Patagonian riparian environments. [ABSTRACT FROM AUTHOR]