Data from: Differential responses by stream and riparian biodiversity to in-stream restoration of forestry-impacted streams

1. Forestry can have detrimental impacts on stream ecosystems,
particularly via excessive sedimentation. A key challenge to stream
management is therefore to identify the best restoration practices to
mitigate the harmful impacts of fine sediments on stream biodiversity and
ecosystem functioning. 2. We studied the effects of restoration of
sediment-impacted headwater streams on the habitat structure, hydrologic
retention, biodiversity (microbes, bryophytes, benthic macroinvertebrates,
riparian plants) and ecosystem functions (periphyton accrual rate and leaf
breakdown) by comparing four treatments: wood-restored, boulder-restored,
impacted (by fine sediments) and near-natural streams. The restored
streams were sampled three to seven years post restoration. Restoration by
wooden or boulder structures aimed to reduce deposited sediments and
increase channel heterogeneity and hydraulic retention. 3. Wooden
structures were ineffective in removing fine bed sediments and did not
induce positive responses in aquatic biota. Boulder additions reduced
substrate limitation and thereby proved beneficial for aquatic bryophytes.
Benthic macroinvertebrates were clearly impaired by sedimentation but
responded weakly to restoration. Leaf-decomposing microbes and ecosystem
functions were unresponsive to restoration but neither did they differ
between near-natural and impacted streams, suggesting that they were
little harmed by sedimentation. 4. Wood addition enhanced hydraulic
retention, and riparian plant assemblages along wood-restored streams
resembled those in near-natural streams, suggesting that increased
retention re-established a more natural flood regime. By contrast,
riparian plant assemblages in boulder-restored streams did not differ from
those in impacted streams. Synthesis and applications. Restoration
improved several aspects of stream and/or riparian biodiversity, but had
limited effects on ecosystem functions. Different restoration measures
resulted in differing biodiversity outcomes: boulder addition was more
effective at restoring in-stream heterogeneity and aquatic biodiversity,
whereas wooden structures helped restore channel hydrology and
retentiveness, and, consequently, riparian vegetation. Therefore applying
both measures in the restoration of forested headwater streams with
naturally stony substrates enhances stream habitat variability at the
watershed scale, providing the most promising scenario for biodiversity
benefits in broad-scale restoration designs. In-stream restoration that
increases hydraulic retention has impacts that extend beyond ecosystem
boundaries, reinforcing the need to restore, manage and protect streams
and their riparian forests in an integrated effort.