Most headwater streams have short intermittent flood-pulsing, but impacts of this flood regime on plant community structure in riparian wetlands are poorly understood. We tested how flood-pulsing caused changes in plant communities by controlling the duration and frequency of inundation in wetland mesocosms (10 m x 20 m). In a flood pulse treatment, water levels fluctuated naturally in response to floods from storm events. In a static treatment, mesocosms were held at stable water levels. We sampled riparian plants growing on the mesocosm banks in low, mid and high elevation zones in each treatment. Plant species assemblages were compared among treatments and elevation zones with NMDS ordination. Community attributes (biomass, richness, percent cover, wetland indicator status and bare ground) were analyzed with 2-way ANOVAs.
Results/Conclusions
Differences in hydrology strongly affected plant community structure in all elevation zones. Flood pulse wetlands were dominated by obligate wetland plants and had large areas of bare ground. static wetlands were dominated by facultative wetland, facultative and upland plants and had a higher abundance of non-native plants. Plant biomass was highest in frequently flooded low elevation zones. This study illustrates that even short and stochastic flooding found in headwater creeks can strongly affect riparian plant community structure.