Impacts of riparian vegetation on hydrological processes

The main impacts of riparian vegetation on hydrological processes are brief ly reviewed in order to highlight needs and perspectives for research and m anagement goals. This review is based upon three distinct influences of rip arian vegetation on hydrological processes: (i) the control of runoff, i.e. the physical impact of living and dead plants on hydraulics, (ii) the impa ct of plant physiology on water uptake, storage and return to the atmospher e, and (iii) the impact of riparian vegetation functioning on water quality . Riparian vegetation influences runoff through complex hydraulic interacti ons during baseflows as well as overbank flows. The contribution of fine ve getational structures to landscape hydrological roughness needs to be consi dered in relation to the spatial complexity (patchiness, vertical stratific ation, rhizosphere) and temporal variability (phenology, succession) of pla nt communities. With the exception of some woody species, the uptake, stora ge and return of water to the atmosphere is poorly known for riparian commu nities, and therefore the assessment of the regional hydrological importanc e of the riparian corridor remains difficult to estimate. Although better u nderstood than the above two influences of riparian vegetation on hydrologi cal processes, there are still a number of unresolved issues concerning the role of riparian vegetation in controlling water quality. In particular, l ittle is known about the coupling of microbial and vegetational functions i n nutrient cycling and the dynamics of carbon release from coarse and fine plant debris. The influence of vegetation complexity and plant diversity on both qualitative and quantitative aspects of water cycling remains an impo rtant area for future research. Fundamental and management issues are ident ified in relation to the use of riparian vegetation as a model and as a too l. Copyright (C) 2000 John Wiley & Sons, Ltd.