Forest Investment Account (FIA) - Forest Science Program
FIA Project Y091136

    Relations between riparian disturbance and habitat attributes in the Southern Interior of BC
Project lead: Wei, Adam (University of British Columbia)
Contributing Authors: Wei, Adam; Chen, Xiaoyong
Subject: Forest Investment Account (FIA), British Columbia
Series: Forest Investment Account (FIA) - Forest Science Program
This is a long-term research installation that specifically supports designing of riparian management strategies and development of sustainability indicators (the Okanagan-Shuswap Land Resource Management Plan and FRPA), and provides critical information for forest resource management and watershed protection. The project has an extension component, has support from an aboriginal community, and can be used to study broad ecological implications of mountain pine beetle (MPB) infestations, wildfire disturbance and timber harvesting. It will also allow critical evaluation of the ecological differences in several key habitat indicators in riparian and aquatic environment between natural disturbance (i.e. MPB infestation) and timber harvesting so that riparian buffers are designed in a broad context.

In-stream wood or large woody debris (LWD) and its ecological significance are well recognized. It influences channel morphology, the composition of riparian vegetation, nutrient and organic matter dynamics, vertebrate communities and fish habitat. Because of its significance, many jurisdictions have identified LWD as an important aquatic habitat indicator for sustainable forest management practices and watershed protection. In the Okanagan-Shuswap Land Resource Management Plan (LRMP), it is clearly stated that a suitable loading level of LWD must be maintained for protection of aquatic habitat. However, how much LWD loading is a suitable threshold for a healthy stream is largely unexamined. It is widely accepted that suitable thresholds of habitat indicators must be assessed or defined in a disturbance or dynamics context (Lertzman and Fall, 1988). This is particularly relevant for LWD as it is highly variable in space and time in aquatic ecosystems.

With FSP funding support, a long-term experimental installation was established in 2005 to assess LWD recruitment, transport, and its interactions with aquatic habitat under wildfire disturbance and MPB infestation in the Southern Interior of BC. This experimental installation is composed of 12 stream reaches including 3 wildfire (the Okanagan Mountain Park Fire) sites and 3 control sites in the Interior Douglas-fir (IDF) biogeoclimatic zone, and 3 MPB infestation sites and 3 control sites in the Montane Spruce (MS) zone. Because the Okanagan Mountain Park Fire occurred in the IDF zone, the selected 3 wildfire sites and 3 control sites in the IDF are comparable. The same is true for the 3 MPB infestation sites and 3 control sites in the MS zone. For this proposed project we will expand this experimental installation by adding 3 MPB salvage-logging sites in the MS zone in order to compare the difference between harvesting and natural disturbance (MPB infestation). Sufficient candidate watersheds (i.e. Weyman, Chase, Beak etc.) are available for selecting salvage-logging sites (Don Dobson, personal communication). Thus, a total of 15 riparian sites and associated stream reaches will be included in this proposed project (see attached Figure 1).

For establishment of the long-term experimental installation in 2005, riparian vegetation conditions and physical channel characteristic such as bankfull depth, width, slope, substrates, pool/riffle etc. were measured at each selected stream reach (100 m). For each LWD piece within the study reaches, the diameter, length, orientation, submersion, function, decay state and input mechanism were documented. The location of each piece of LWD was recorded by total station survey method. The tag method (Berg et al. 2002) was used to monitor LWD input and transport. That is, all LWD pieces within each reach were tagged in two places with numbered metal disks that uniquely identify each piece. The tagged disks will allow identification of the LWD over successive years to determine recruitment, transport and movement of LWD within or out of the reaches studied. All above data will be measured annually. Additionally, LWD related habitat attributes such as residual pool depth, percent cover for vertebrates and substrate composition are monitored.

To explicitly link riparian disturbance to biological functions and communities, we will add two additional elements in this project. Specifically, we will measure how organic matter flux (export) is affected by three disturbance treatments (wildfire, MPB infestation and salvage logging). In addition, we will conduct seasonal (fall/winter and spring/summer) snorkel surveys in study reaches to determine whether the abundance and diversity of aquatic vertebrates differs as a function of different disturbance regimes. Suspended organic matter serves as an important food source for a variety of stream vertebrates thereby linking organic matter flux to upper trophic levels such as fish and amphibians. A number of studies have shown that riparian disturbance and LWD abundance affects the distribution and abundance of vertebrates especially salmon, trout and char (Bisson et al. 1987). Therefore, fire, MFB infestations and harvesting may directly affect the distribution and abundance of stream vertebrates or indirectly by affecting LWD inputs.

The project will generate critical data on the effects of various riparian disturbances on LWD dynamics, aquatic habitat and vertebrates in the Southern Interior of BC. An annual budget (i.e. input-output) of LWD in the aquatic/riparian ecosystems will be established. These data will help determine the sensitivity of riparian and aquatic functions to various disturbances. They will also help quantify if LWD is a suitable habitat indicator in the Southern Interior of BC, and if so, what the suitable loading thresholds would be in each disturbance regime. This project will expand our scientific and management scopes by providing critical information regarding the role that forest disturbance plays in riparian and stream environments. It will support policy, regulation and guideline development

The proposed research addresses the following key scientific questions:
1). What are the impacts of three riparian disturbance treatments on both terrestrial riparian and aquatic habitat?
2). What are the ecological differences between natural disturbance (MPB infestation) and human disturbance (salvage logging)?
3). What are the average annual rates of wood recruitment and transportation in disturbed and intact headwater forest streams in Southern Interior of British Columbia?
4). What is the interaction between riparian disturbance, LWD loadings and aquatic habitat attributes?
5). How do riparian disturbance and LWD loadings and aquatic habitat attributes affect organic matter flux and vertebrate communities?
Related projects:  FSP_Y102136FSP_Y113136


Final Technical report (0.7Mb)
Extension note (0.3Mb)

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Updated May 02, 2011 

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