Ecosystem recovery in restored headwater streams: the role of enhanced leaf retention
Article first published online: 26 JUN 2002
Journal of Applied Ecology
Volume 39, Issue 1, pages 145–156, February 2002
How to Cite
Muotka, T. and Laasonen, P. (2002), Ecosystem recovery in restored headwater streams: the role of enhanced leaf retention. Journal of Applied Ecology, 39: 145–156. doi: 10.1046/j.1365-2664.2002.00698.x
- Issue published online: 26 JUN 2002
- Article first published online: 26 JUN 2002
- Received 15 March 2001; final copy received 8 November 2001
- aquatic mosses;
- benthic invertebrates;
- ecosystem-level responses;
- forest streams;
- leaf litter;
- stream restoration;
- substrate heterogeneity
- 1There is controversy over how the success of ecological restoration should be measured. Traditionally, emphasis has been placed on species diversity and other community attributes, whereas the restoration of ecosystem processes has received less attention. Here, we combine replicated field experiments and a field survey to provide an ecosystem-level measure of stream restoration success.
- 2Numerous headwater streams in Finland, and in many other parts of the world, have been channelized for timber transport, resulting in channels with simplified structure and flow. Recently, programmes have been launched to restore these streams to their pre-channelization condition. While the efficacy of restoration in improving fish habitat has been tested, little is known about effects on other stream biota or on the retention of leaf litter, despite its importance in trophic dynamics of forested headwater streams. Using a before-after-control-intervention (BACI) designed experiment with multiple reference and experimental streams, we examined restoration-induced changes in retention efficiency by conducting leaf-release experiments before (1993) and after (1996) restoration.
- 3Substrate heterogeneity increased, but moss cover decreased dramatically following restoration. Retention efficiency in restored streams was higher than in channelized, but lower than in natural, streams. Algae-feeding scrapers were the only macroinvertebrate group whose density increased significantly after restoration.
- 4Aquatic mosses were a key retentive feature in both channelized and natural streams, but their importance to retention was strikingly reduced by restoration. During restoration work, mosses are detached from large areas of the stream bed, exposing bare stone surfaces for colonization by periphytic algae.
- 5A more effective restoration technique would involve the use of moss transplants, or the addition of large woody debris, to increase retentiveness and thus enhance the availability of organic material to benthic consumers. This case study on rivers illustrates how restoration projects benefit from an ecosystem perspective and from measures of ecosystem processes in assessing restoration success.