Forest Investment Account (FIA) - Land Base Investment Program
FIA Project 6736001

    Small Stream Study
Project lead: Robertson, Ian (Forsite Consultants Ltd.)
Subject: Forest Investment Account (FIA), British Columbia
Series: Forest Investment Account (FIA) - Land Base Investment Program
Allochthonous input1 is an important source of food and energy to stream systems (Culp and Davies 1985, Hollingsworth 1988, Alan 1995, May et al. 1997, Wenger 1999, Cole et al. 2003, MacKenzie and Moran 2004), and is a primary component of organic material in small streams (Lowe et al. 1986, Hollingsworth 1988). In this project (Clayoquot Sound) we annually monitor the amount (mass (g)), nutrients (mg) (Potassium, Nitrogen and Phosphorous), and composition (wood, needles, cones, leaves and other organic material) of allochthonous material that is naturally introduced into small streams. The study is divided into four components: a
chronosequence study of different second growth conifer forest age classes, different variable retention (VR) timber harvest regimes (with and without a five metre riparian reserves), three deciduous riparian vegetation types, and an intact late seral (old growth) forest control. There are many interesting results that have come from the first two years of a broad sampling regime. In particular are the mass contributions from site SB (30% retention with a 5 m riparian reserve), and from the second growth sites GB and GB2 (age class 21-35), W (age class 36-50) and W2 (age class 51-65) that are all relatively equivalent (or greater) to the intact old growth sites (7B2, 7B and 8). Of the three old growth sites, Site 8 registered less mass than the other two, yet seemed to compensate with higher nutrient concentrations. Nutrient value (potassium, nitrogen
and phosphorous) associated with site SB remained consistent with the intact old growth sites, as did site LS, which has a 30% retention level without a riparian reserve. Nutrient value of allochthonous material in the second growth sites GB, GB2, W and W2 significantly surpassed that of the intact old growth sites. The consistency of mass and nutrient levels in SB (when compared to the old growth sites) implies that no more than a 5m riparian reserve may be initially required for equivalent allochthonous mass and nutrient input, bringing the FEMAT charts (figure 3), and Chen (1991) and Culp (1982) reserve width specifications into question. As well, the apparent relatively quick recovery of allochthonous mass and nutrient contribution in the second growth age classes may indicate that the absence of riparian reserves may have limited effect on
stream health at the watershed level, especially under current harvesting regimes where the amount of watershed area that can be harvested over a given period is limited by several legislative constraints. However, after just two years of monitoring, the results cannot be interpreted as conclusive and further monitoring should be done to document statistically significant results and trends.
Related projects:  LBIPI_6884001
Contact: Robertson, Ian, (250) 926-9177,

Updated August 16, 2010 

Search for other  FIA reports or other Ministry of Forests and Range publications.

Please direct questions or comments regarding publications to