ECOSYSTEM ENGINEERS MODULATE EXOTIC INVASIONS IN RIPARIAN PLANT COMMUNITIES BY MODIFYING HYDROGEOMORPHIC CONNECTIVITY

• Published in: River research and applications 2014-01, Vol.30 (1), p.45-59
• Main Authors: Corenblit, D., Steiger, J., Tabacchi, E., González, E., Planty-Tabacchi, A-M
• Format: Article
• Language: English
• Subjects: Animal and plant ecology; Animal, plant and microbial ecology; Applied ecology; Biodiversity and Ecology; Biological and medical sciences; Conservation, protection and management of environment and wildlife; Ecology, environment; ecosystem engineer; Ecosystems; Environmental Sciences; exotic species; Fresh water ecosystems; Fundamental and applied biological sciences. Psychology; General aspects; hydrogeomorphic disturbance; invasibility; Life Sciences; Mediterranean riparian system; Parks, reserves, wildlife conservation. Endangered species: population survey and restocking; species richness; Synecology
• ISSN: 1535-1459; 1535-1467
• DOI: 10.1002/rra.2618

ABSTRACT Patterns of native and exotic plant species richness and cover were examined in relation with ecosystem engineer effects of pioneer vegetation within the Mediterranean gravel bed river Tech, South France. The floristic composition was characterized according to two distinct vegetation types corresponding to two habitats with contrasted conditions: (i) open and exposed alluvial bars dominated by herbaceous communities; and (ii) islands and river margins disconnected from annual hydrogeomorphic disturbances and covered by woody vegetation. A significant positive correlation between exotic and native plant species richness and cover was observed for both vegetation types. However, significant differences in native and exotic species richness and cover were found between these two vegetation types. Higher values of total species richness and Shannon diversity were attained within the herbaceous vegetation type than within the woody type. These differences are most likely related to changes in local exposure to hydrogeomorphic disturbances driven by woody engineer plant species and to vegetation succession. A lower exotic species cover within the woody vegetation type than within the herbaceous type suggested an increase of resistance to invasion by exotic species during the biogeomorphic succession. The engineer effects of woody vegetation through landform construction resulted in a decrease of alpha (α) diversity at the patch scale but, in parallel, caused an increase in gamma (γ) diversity at the scale of the studied river segment. Our study corroborates recent investigations that support the theory of biotic acceptance of exotic species by native species at the local scale (generally