Stream characteristics and their implications for the protection of riparian fens and meadows

Abstract

1. Running waters, including associated riparian areas, are embraced by international legal frameworks outlining targets for the preservation, protection and improvement of the quality of the environment. Interactions between stream and river processes and riparian habitats have not received much attention in the management of stream ecosystems, and integrated measures that consider both the ecological status of streams and rivers (sensu EU Water Framework Directive, WFD) and the conservation status of riparian habitats and species (sensu EU Habitats Directive, HD) are rare. 2. Here, we analysed the influence of stream size, morphology and chemical water characteristics for the distribution of water-dependent terrestrial habitat types, i.e. alkaline fens, periodically inundated meadows and meadows in riparian areas in Denmark using an extensive data set covering a total of 254 stream reaches. A species-based classification model was used to translate species lists into a standardised interpretation of habitat types protected by the HD in Denmark. 3. No size dependency was found regarding the distribution of fen and meadow vegetation. Instead, the distribution of fen and meadow vegetation was strongly affected by the morphology of the streams. Alkaline fens, periodically inundated meadows and meadows occurred six, five and four times, respectively, less frequently along channelised compared with natural stream reaches. Our results indicate that stream channelisation strongly interfered with the natural hydrology of riparian areas, affecting conditions needed to sustain protected fen and meadow communities. 4. We also found that water chemistry strongly influenced the occurrence of fen and meadow vegetation in riparian areas. The probability of finding fen and meadow vegetation was reduced when total phosphorus (TP) concentration exceeded 40-50 lg P L )1 , whereas meadow vegetation responded less strongly to TP. 5. Our findings highlight the importance of restoring hydrology of riparian areas to improve conditions for fen and meadow vegetation, but also that the water chemistry should be considered when measures that increase hydrological connectivity result in an increase in the probability of flooding.

Effects of stream flooding on the distribution and diversity of groundwater‐dependent vegetation in riparian areas

“…Riparian areas of lowland streams, although naturally rich in nutrients, are often affected by agricultural activities resulting in eutrophication. The negative impacts of eutrophication on riparian vegetation are widely recognised in the literature (Lamers et al, 2006;Banach et al, 2009;Baattrup-Pedersen et al, 2011;Klaus et al, 2011), and therefore, we were surprised that our study failed to reveal a negative impact of low flood frequency on the distribution and diversity of protected rich fen vegetation in Danish lowland riparian areas. Rather, low frequency flooding was found to stimulate species richness and the growth of low productive species within the rich fen areas.…”

“…Stream channel morphology can play a crucial role for the aquatic and groundwater‐dependent riparian habitats included in article 6 of the WFD (Hammersmark et al. , 2009; Baattrup‐Pedersen et al. , 2011; Loheide & Booth, 2011).…”

“…Stream channel morphology can play a crucial role for the aquatic and groundwater-dependent riparian habitats included in article 6 of the WFD (Hammersmark et al, 2009;Baattrup-Pedersen et al, 2011;Loheide & Booth, 2011). Therefore, effects of morphological alterations on these habitats should be considered together with those on instream habitats in restoration planning and management.…”

Species Recruitment following Flooding, Sediment Deposition and Seed Addition in Restored Riparian Areas

“…We used a species‐based classification model to characterize the vegetation in the areas. This model has been developed to achieve a statistical and standardized interpretation of plant community types for application in monitoring, assessment, and restoration in Denmark (Nygaard et al 2009; see Baattrup‐Pedersen et al 2011 for more details). The vegetation in areas A and B was fen/fen‐meadow vegetation, whereas the vegetation in area C was degraded meadow vegetation.…”

Climate change effects on lowland stream flood regimes and riparian rich fen vegetation communities in Denmark

“…In the investigated streams total nitrogen concentrations varied between 3.3 and 7.4 mg L -1 and total phosphorus concentrations between 105 and 143 µg L -1 . We believe that these concentrations may pose a risk for a range of low productive fen species (Bedford et al 1999, Baattrup-Pedersen et al 2011, 2014. Furthermore, flooding during summer may have a stronger effect on soil biogeochemical processes than flooding during winter, because elevated temperatures enhance microbial conversion rates and, with that, nutrient cycling within the areas.…”