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Responses of riparian plants to increases in habitat quantity and quality following restoration of channelized streams
Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences. (Landscape ecology)ORCID iD: 0000-0003-3896-8466
Mendel University.
Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences. (Landscape ecology)
(English)Manuscript (preprint) (Other academic)
Abstract [en]

We evaluated the ecological effects of stream restoration by comparing riparian vascular plant diversity and riparian habitat properties between channelized stream reaches and reaches restored with two different techniques in northern Sweden. Channelized streams were modified >50 years ago to facilitate timber floating which implied straightening and clearing channels from in-stream boulders and wood, which were deposited in riparian areas. Traditionally restored reaches underwent restoration efforts 8-10 years ago when material from the riparian zones was returned back to the channels. Some reaches were re-restored 3 years before our study by bringing large structural elements (boulders and downed trees) to the previously traditionally restored streams. These three restoration types (i.e., channelized, traditionally restored, and re-restored) represent a gradient in habitat complexity and we tested whether they also represent a gradient in plant diversity, and habitat quantity and quality. Riparian plant cover was higher at both restored types than channelized reaches. Responses of riparian plant diversity to restoration were scale dependent, with higher species richness at both restored types than channelized reaches at plot scale level (0.25 m2), whereas at the reach (>700 m2 of riparian area) and transect scales, plant species richness did not differ among the three restoration types. Differences in plots scale richness were largest in the most dynamic and species-rich part of riparian zones, i.e., at 20 and 40 cm elevations above the low summer water levels. We found no systematic differences in plant cover and species richness between the two restored types. Species composition did not differ among the restoration types at the reach scale, but at the plot scale species composition segregated between channelized and restored reaches but with small compositional differences between the traditionally restored and re-restored types. Aspects of both riparian habitat quantity and quality for vascular plants increased after restoration. Riparian zones along re-restored reaches had the highest amount of soils available for plant establishment in comparison to traditionally restored and channelized streams. In contrast, soil quality was more favorable to plants along channelized reaches, with higher soil pH and lower C:N ratio at some riparian levels. The magnitude of floods did not differ between the three types of streams, but inundation duration significantly increased following restoration with the longest inundation events at re-restored reaches. Thus, given that inundation is positively associated with plant species richness in riparian zones, habitat quality may have improved following restoration. We conclude that restoration of channelized streams has improved the abundance and diversity of riparian vascular plants. Given that we observed several positive trajectories in biotic and habitat recovery (although statistically insignificant in some cases) and that the new re-restoration technique is predicted to enhance riparian habitat conditions more effectively than traditional methods, we suggest that with time, further recovery of riparian vegetation may occur.

Keyword [en]
channelization, habitat quality and quantity, riparian vegetation, stream restoration, vascular plants
National Category
Ecology
Research subject
biology, Environmental Science
Identifiers
URN: urn:nbn:se:umu:diva-100216OAI: oai:DiVA.org:umu-100216DiVA: diva2:790794
Funder
Swedish Research Council Formas
Available from: 2015-02-25 Created: 2015-02-25 Last updated: 2015-03-04
In thesis
1. Grow with the flow: Hydrological controls of riparian vegetation in boreal stream networks
Open this publication in new window or tab >>Grow with the flow: Hydrological controls of riparian vegetation in boreal stream networks
2015 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

What drives species diversity across landscapes is one of the most fundamental questions in ecology. Further, understanding the mechanisms underlying species diversity patterns is important not only for forming and challenging ecological theories but also essential for appropriate landscape management and effective nature conservation. This thesis focuses on patterns of vascular plant, moss and liverwort species richness and composition in relation to water flow in boreal-forest catchments, focusing mostly on riparian zones (RZs), that is terrestrial areas bordering streams and rivers. I addressed some of the most essential questions related to the ecology of riparian vegetation including the role of stream network position, groundwater (GW) flow paths, substrate availability, upland perturbations, and stream restoration. I also investigated how riparian soil processes and habitat properties relate to these factors in order to provide a holistic understanding of riparian dynamics. The results showed that the species richness and composition of riparian vascular plants, mosses and liverworts are strongly influenced by position along the stream network, GW discharge, presence of variable substrates in RZs, and by stream restoration. Generally, more species were found downstream in the network, at sites with inputs of upland GW, sites with high diversity of substrates (e.g., open mineral soil, rocks, stones, wood and bark), and along streams restored after channelization. This thesis also describes how riparian habitat properties responded to position in the landscape and human impacts, thus providing mechanistic links between plant species diversity and riparian processes across spatial scales. These ecological insights are further implemented into numerous recommendations for freshwater and upland management in boreal Sweden. Given that streams and rivers connect landscape elements both longitudinally and laterally I argue that management plans should be designed for entire catchments instead of individual river segments. Ignoring the connectivity of streams as well as the high connectivity of riparian areas to uplands via GW flows may result in failure of restoration, mitigation and/or protection actions. Further, during forestry operations more emphasis should be placed on GW discharge areas along streams and rivers, because they represent important ecological and biogeochemical hotspots in the landscape. The riparian buffers left along streams in boreal catchments affected by forestry are presently insufficiently wide and often uniform in width. This threatens the assemblages of species in GW discharge hotspots and the ecosystem services they provide. Overall, this thesis describes a holistic picture of riparian diversity patterns and riparian processes in boreal landscapes, acknowledges and elaborates on current ecological theories, presenting new patterns in biodiversity, and offers management guidelines. 

Place, publisher, year, edition, pages
Umeå: Umeå Univeristy, 2015. 27 p.
Keyword
boreal forest, channelization, groundwater, Krycklan catchment, liverworts, mosses, riparian buffers, riparian vegetation, river restoration, species richness, stream network, stream size, vascular plants
National Category
Ecology
Identifiers
urn:nbn:se:umu:diva-100217 (URN)978-91-7601-212-3 (ISBN)
Public defence
2015-03-26, Björken, Sveriges lantbruksuniversitet, Skogsmarksgränd 901 83, Umeå, 10:00 (English)
Opponent
Supervisors
Funder
Swedish Research Council Formas
Available from: 2015-03-05 Created: 2015-02-25 Last updated: 2015-03-09Bibliographically approved

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