Ivan Bernez

Relationships between macrophytic vegetation and physical features of river habitats: the need for a morphological approach

The aim of this paper is to study the relationships between the physical features of rivers and the distribution of macrophyte vegetation. Field work was undertaken at 207 stations along the Scorff River and its tributaries, a salmon river system in southern Brittany (western France). The physical features were considered using a principal component analysis (PCA). Stepwise multiple regression models made it possible to assess their relationships with the botanical data. The first five axes of the physical PCA (used as explicative variables) were initially linked to the most frequently surveyed species, then to their eco-morphological types, and, finally to Arber’s (1920. Water Plants. A Study of Aquatic Angiosperms. Cambridge Univ. Press, Cambridge, 414 pp) morphological classification. It was concluded that plant morphology was closely related to these environmental factors. This could contribute to the development of predictive models for plant distribution and could increase the knowledge of reference vegetation related to bioindication systems.

Invasive river plants from Portuguese floodplains : What can species attributes tell us?

Biological traits of aquatic and riparian plants were compared among invasive and non-invasive groups of species from both native and exotic taxa in Portuguese fluvial systems. Twenty-six riparian and aquatic species were selected and their frequency of occurrence and foliar percentage cover was analysed at 401 sampling sites on the main catchments of Central and Southern Portugal. Canonical correspondence analysis and a hierarchical clustering were applied to the species traits data set. No typical invader profile emerged from the analyses. However, some specific attributes were clearly related to the alien and native plant invasiveness, such as vegetative reproduction, fragment viability and life span. The results of the present work could help with the early detection of invasive plant species in Portuguese fluvial corridors.

Invasibility patterns of knotgrass (Paspalum distichum) in Portuguese riparian habitats.

Spatial patterns of the exotic riverine knotgrass (Paspalum distichum L.) were examined in Mediterranean river basins in Southwestern Iberia. The major goals of this study were to assess the degree of invasibility of riparian habitats by this species and to determine the influence of environmental factors and human-induced disturbances that this knotgrass has on both the landscape and the habitat scales. The present study demonstrates the ability of knotgrass to invade riparian habitats in Portuguese freshwater ecosystems. However, most of the spatial variation of the knotgrass cover seemed to be driven by local factors, such as fine sediment enrichment and the fragmentation of riparian woods, and by other anthropogenic interferences in relation to both the fluvial system and the surrounding landscape. Nomenclature: Knotgrass, Paspalum distichum L. #3 PASDS. Additional index words: Exotic species, human disturbances, environmental variables, PASDS, Mediterranean basin.

River management and habitat characteristics of three sympatric aquatic rodents: common muskrat, coypu and European beaver

The ecological environment of three aquatic rodents was studied in the French Ardennes region. Two species, the coypu (Myocastor coypus) and the common muskrat (Ondatra zibethicus), are invasive. By contrast the native European beaver (Castor fiber) was extirpated from the region, subsequently reintroduced, and currently is protected. The aim of this study was to compare the ecological requirements of these three species and predict their future range distributions. We studied the relationship between the species and describe the characteristics of waterways and riparian vegetation in 29 sampling sites. Coypus and muskrats were observed in a variety of riparian habitats and their probability of detection appeared to be independent of waterway width, bank height or bank slope. The availability of numerous herbaceous plants, known to be consumed by these species, may facilitate their settlement. Muskrats are widespread on the French Ardennes waterways, but coypus have not yet colonised the northern part of the region. On the other hand, the beaver was observed primarily in the widest waterways with high banks, where woody plant species, such as Betula, Carpinus and Fraxinus, are found in abundance. Potentially favourable sites for beaver and coypu settlement were analysed to suggest appropriate management according to each species’ status. However, the number of sample sites is weak, especially for sites with beaver, limiting our conclusion.

How past riparian management practices can affect composition and structure of vegetation for headwater ecological restoration projects

Abstract Ecological restoration of river networks, especially of headwaters, is a key issue to improve water ecological, chemical and physical qualities and ecological functioning of aquatic ecosystems. Ecological restoration of degraded riparian vegetation is commonly considered as an efficient way to improve headwater habitats. This study aims to describe past management dynamics and their effect on current riparian vegetation structure and composition. We focused on two headwater brooks surrounded by traditional pasture in the rural catchment of the river Oir, a salmonid nursery of the river Sélune, Normandy, France. Historical riparian vegetation dynamic has been characterized thanks to interpretation of ortho-photographs from 1947 to 2010. GIS analyses allowed us to distinguish five types of management practices from stable vegetation (maintained open or maintained woody) to heterogeneous dynamic vegetation (alternation of clear-cutting, coppice management and recolonization by ligneous species). To measure their impact on the riparian ecosystem, past management practices were linked with field data describing current structure and composition of riparian vegetation. Results show that structure of riparian plant communities depends mainly on recent management practices, while floristic composition depends both on recent and past management practices. Knowledge of the past dynamics of riparian landscapes proves to be a relevant indicator of the ecological status of headwater ecosystems that could be used to improve ecological restoration instead of classical management practices of riparian vegetation.