Objectives
Western Forest Products has been fertilizing western red cedar (Thuja plicata) and western hemlock (Tsuga heterophylla) operationally to address the severe chlorosis and growth check seen in regenerating stands on S1 cedar-hemlock (CH) sites for more than a decade. Results of the Salal Cedar Hemlock Integrated Research Program (SCHIRP) demonstrated the beneficial effect of fertilization on these sites.
Location
Coal Harbour and Holberg, northern Vancouver Island.
(Forest Renewal British Columbia Region - Pacific Region; Ministry of Environment, Lands and Parks Region - Nanaimo Region; Ministry of Forests - Vancouver Region)
Introduction
SCHIRP is based on partnerships among individuals from Western Forest Products Ltd., Macmillan Bloedel, TimberWest, Canadian Forest Service, BC Ministry of Forests, University of Victoria, and University of B.C. Departments of Botany, Soil Science and Forest Sciences.
SCHIRP results form the basis for operational fertilization programs on salal-cedar sites. Decisions as to site preparation and planting CH sites have also been influenced by SCHIRP results. Findings of high retention of fertilizer P altered the fertilizer practice of repeated P additions. Individual tree fertilizer packs have been developed based on SCHIRP results. Investigations of nutrition of these N-deficient sites have led to development of trials to test unconventional silvicultural treatments that may be effective on these sites. The dual approach, combining basic research into the nutrition of CH sites and continued monitoring of long-term silvicultural trials will allow us to identify the most effective regeneration strategy for ericaceous sites.
Assessment
Research was conducted to determine silvicultural practices to alleviate the growth problem, and to understand the fundamental cause of the poor nutrition of trees. Field trials have been established and tree growth response to the following treatments is being monitored through crown closure:
We have recently established fertilization screening trials and fertilization-weed control trials in high-elevation cutovers prone to Vaccinium competition.
The following ecological studies have been conducted to better understand the cause of poor nutrient supply and differential response of tree species to silvicultural treatments:
Fertilization Work
Post-fertilization monitoring plots, together with control plots have been established in five areas of TFL 25 Block 4 fertilized in 1995 for a total of 22 plots. One control plot and one fertilized plot are located near the Misty Lake Highway Rest Stop. This area was harvested in 1970 and naturally regenerated to cedar. Measures of all trees were made in early spring of 1995 (end 1994 growing season), at time of fertilization, and two growing seasons later, in the winter of 1997 (end 1996 growing season). Fertilizer was applied aerially.
This plot pair shows the greatest difference in stand density, with the control having twice the number of trees. Other plot pairs were of more uniform density and fertilized plots regularly had higher densities than the control plots.
Fertilization Results
Analysis of all the 1995 Operational Fertilization Monitoring Plots revealed no significant difference in height or diameter at time of establishment. After two growing seasons, heights, height increments, and diameters were significantly greater for the fertilized stands. The mean height increment (one year) was 46.8 cm for the fertilized cedar, and 19.2 cm for the unfertilized cedar. Fertilized cedar grew at 244 per cent the rate of height growth of the control cedar. The mean height increment (one year) was 45.6 cm for fertilized hemlock and 14.1 cm for unfertilized hemlock. This represents a 323 per cent improvement in growth rate.
SCHIRP results are summarized in two synthesis reports available on the SCHIRP website (http://www.forestry.ubc.ca/schirp/homepage.html). The results have been incorporated into a field guide for regeneration of salal-cedar sites which is available from the SCHIRP coordinator, Cindy Prescott (cpres@interchange.ubc.ca).
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