Waterbodies and the immediate adjacent environment are linked by the exchange of water, material, and organisms. Functioning riparian ecosystems provide many of the essential attributes required by fish and other aquatic organisms, including shade, bank stability, protection from flood events, and a recruitment source of large woody debris and coarse woody debris. Approximately 72 percent of terrestrial vertebrates utilize riparian areas highly (CSSP, 1995). Non-functioning (or impaired) riparian ecosystems supply poor bank protection and are a poor recruitment supply of large woody debris. Impaired riparian ecosystems will eventually recover, but the process would take centuries.
In the past, cut blocks were logged right to stream banks, which virtually eliminated any chance of larger trees dying and falling into the stream. In many cases red alder and brush have taken over the riparian areas of the streams and rivers. While alder can supply good cover, when it dies and falls in the stream it breaks down quickly (conifers are far more resilient). In CWFS riparian rehabilitation projects, there is a strong focus on developing a new, uneven aged coniferous (or mixed coniferous-deciduous) riparian zone with abundant and diverse understory vegetation.
Riparian Vegetation Types (RVT’s) are broken into 5 basic classifications
- RVT 1: Brush dominated, with poorly stocked conifer component
- RVT 2: Overstocked conifer
- RVT 3: Deciduous forest over top of a good conifer understory
- RVT 4: Deciduous forest with a poor conifer understory
- RVT 5: Old growth or very old second growth forest
Each sub-basin requires stratification of the different RVT types. There can then be a focus of treatments of the highest priority RVT’s. RVT 4 is the highest priority for treatment to have maximum immediate benefit for fisheries habitat while RVT 2 is the highest priority for immediate benefit to terrestrial species. These RVT’s can be treated to enhance habitat attributes for focal species identified wildlife species for the Clayoquot Sound area.
The image above was captured in an RVT 4 deciduous forest with a poor conifer understory. The restoration crew member is girdling red alder, removing a ring of bark from the tree to allow it to die back slowly. Red alder and salmonberry can effectively out-compete conifer seedlings for light, water and nutrients. In some areas, alder have effectively suppressed conifer regeneration facilitating establishment of a salmonberry dominated regime (RVT 1). A brush dominated site can suspend seral stage development by several hundred years.
As a result of these characteristics, RVT 4 represents the highest opportunity and priority for restoration. The objective of riparian restoration in RVT 4 is to re-establish conifers, through planting or release of existing conifers, within the riparian zone to stabilize the channel, reduce bank erosion, and provide a long term recruitment source of LWD. The desired outcome is the establishment of an uneven aged mixed coniferous-deciduous riparian zone.