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Research Branch > Stand Management > Fertilization or
Juvenile Thinning > EP 886.01d
Fertilizer x Thinning Interactions in
Lodgepole Pine (EP 886.01d)
Many experiments have compared fertilization growth responses in thinned
and unthinned stands. However, few studies have examined the effects of
fertilization across a range of post-thinning densities. Given the large
impacts of juvenile thinning on stand structure and development, it is
likely that the level of post-thinning density may also affect tree and
stand growth following fertilizer application.
In 1992, the BC Ministry of Forests, Research Branch established an
experiment to determine the effects of different levels of post-thinning
density, with and without repeated fertilization, on the growth and
development of young, harvest-origin lodgepole pine. The site is located
southeast of Williams Lake within the moist-cool subzone of the SBPS
biogeoclimatic zone. The unthinned, harvest-origin stand was approximately
10 years old at the time of installation establishment.
To determine the effects of different post-thinning stand densities on
the growth and development of unfertilized and fertilized lodgepole pine,
and to examine the nature of fertilizer x thinning interaction.
Factorial combinations of three post-thinning densities (600, 1100, and
1600 stems per hectare) and two levels of fertilization (unfertilized,
fertilized) are replicated three times and arranged in a completely
randomized design. Treatment plots are rectangular, and vary in size from
0.09 to 0.24 ha depending on post-thinning density. Each treatment plots
consists of an inner, square assessment plot (with 64 tagged trees)
surrounded by a treated buffer. The assessment plot is offset at one end of
the rectangular treatment plot to reserve an enlarged buffer at one end of
the treatment plot for future destructive sampling. There are also three
replicates of small, unthinned control plots that are large enough to
contain at least 200 trees.
A balance fertilizer blend is applied to the fertilized treatment plots
every 5 years. Fertilizer application rates are as follows (kg/ha): 200N,
100K, 100P, 75S, 38Mg, 3B.
This installation is re-measured at 5-year intervals. Measurements
include diameter at breast height, total height, height to live crown, crown
width, tree form and damage). Leaf area development is also being monitored
within each treatment plot. Foliar nutrient data are obtained from all
treatment plots prior to, and one year after, every fertilizer application.
- The National Research Council of Canada grants permission to
individuals to download or print single copies of articles published by
the NRC Research Press. Canadian Journal of Forest Research articles
(starting with vol. 27) can be downloaded from the following website:
R.P. 2001. Fertilization of lodgepole pine in western Canada. In Proc.
Enhanced Forest Management: Fertilization and Economics Conference, March
1-2, 2001, Edmonton, Alta. C. Bamsey (editor). Clear Lake Ltd., Edmonton.
Brockley, R.P. 2005. Effects of post-thinning density
and repeated fertilization on the growth and development of young lodgepole
pine. Can. J. For. Res. 35: 1952-1964. [PDF]