Hotspots for riparian plants

Posted on October 15, 2015

Streamside plants buffer the damaging effects of floodwaters and filter material and nutrients washed down from higher points in the catchment. While these processes are well understood, the effects of seepage and overland flows on riparian plants have been largely overlooked. To explore how streamside plant diversity is affected by groundwater discharge from upland areas, twenty pairs of study sites were established along forest streams of different sizes in northern Sweden. Paired sites were in similar locations 500 m apart, one at a stream bank with upland groundwater discharge and the other at a point with no discharge. At each site the topography was described and transect sampling was used to record plant species. Soil samples were taken for later analysis. Numbers of plant species were significantly (20%) higher at streamside sites with groundwater discharge, and 22% of all the 175 species recorded were found only at those sites. The same discharge sites also had higher soil pH and lower C/N ratios, which suggested that they were receiving beneficial nutrients and cations from the catchment. These trends were similar for streams of all sizes. The study findings have implications for forestry and conservation – for example, areas of high plant diversity could be protected by having wider riparian buffer strips around groundwater discharge areas. Such high-diversity hotspots could also be targeted for stream restoration.

Reference: Kuglerova, L. et al. 2014. Groundwater discharge creates hotspots of riparian plant species richness in a boreal forest stream network. Ecology, 95(3), 715–725.