Data from: Riparian vegetation diversity in boreal headwaters: Comparing streams, modified waterways and ditches

Decades of forest management in the boreal biome have involved digging
drainage ditches and modifying streams to increase timber production,
altering terrestrial ecosystems and expanding stream networks. Modified
waterways and drainage ditches represent widespread novel aquatic and
riparian ecosystems, with little known about their biodiversity. With
approximately 68% of small waterways in Sweden human-made or modified,
improved knowledge is needed to inform effective management of
biodiversity of these often-disregarded habitats. Currently, ditches and
modified waterways may undergo ditch network maintenance, involving the
removal of debris and vegetation, with less emphasis placed on protecting
them with vegetated buffers compared to natural waterways. In this study,
we surveyed riparian vegetation across soil types (till and peat) along a
drainage size gradient (0.5 ha – 60 ha) in a northern boreal catchment,
assessing the riparian vegetation amongst ditches, modified waterways, and
‘natural’ streams. We found that the vegetation in this catchment did not
differ significantly between modified waterways and streams on till soils,
highlighting an important role for modified waterways in maintaining
riparian vegetation diversity. Till ditches exhibited similar community
composition, although significantly lower diversity compared to modified
waterways and streams on till. By comparison, peat ditches harboured less
vegetation diversity, and exhibited lower species turnover and different
community composition, driven by variation in soil conditions and
catchment size. Our study demonstrates that plant species diversity and
richness increase with catchment area along a ditch to stream gradient,
highlighting a pattern well-established in natural systems but
underexplored in the context of artificial and modified waterways. To
enhance vegetation diversity in boreal landscapes, conservation planning
should include modified waterways on till soils. Management
recommendations include avoiding ditch maintenance in self-eroding till
systems and prioritizing the rewetting of sites with peat ditches and
small catchments. Rather than a uniform restoration approach, our results
advocate for catchment-scale planning and tailored ecological endpoints to
maximise biodiversity and ecosystem resilience.