Ecological succession and fine sediment accretion influence local patch dynamics of a pioneer riparian species (Typha minimaHoppe)

Abstract

AbstractChanges in environmental variables induced by ecological succession and hydrogeomorphological processes affects riparian vegetation dynamics along rivers. The biotic and abiotic factors driving local patch dynamics of riparian species is little known for early successional stages.To fill this gap, we examined local patch dynamics and frequency of occurrence of a protected riparian pioneer species (Typha minimaHoppe) and related it to several biotic and abiotic variables along the Isère River (France) from 2016 to 2019.We monitored biotic and abiotic factors related to ecological succession and sediment accretion. We implemented Linear Mixed and Generalized Mixed Models to analyze how environmental factors affected patch boundary dynamics ofT. minima. Finally, we built a Structural Equation Model to describe potential relationships betweenT. minimafrequency, height above mean water level, vegetation cover and composition.We found that a thick layer of silt and sand deposits as well as a moderate herbaceous and low shrub cover layer characterizedT. minimapatch progression close to the mean water level.Typha minimastands did not seem to expand on coarser substrates with lower herbaceous cover. Its maintenance was associated with large silt and sand deposits and high cover of herbaceous plants and shrubs well above the mean water level. The variables characterizing patch regression were not clearly identified. Finally, the interaction between bar height, vegetation cover and succession stage did not explain variations inT. minimafrequency.Our results provide knowledge about the environmental variables associated withT. minimapatch dynamics, which are useful for future conservation and restoration projects. Habitat rejuvenation through restoration of natural river flow regimes could sustain localT. minimatransplantation and large population turnover essential to the conservation of this species.