| dc.description.abstract | The objectives of this investigation were 1) to examine
the duration and pattern of jack pine growth response to urea
fertilization and low thinning, and 2) to examine methods commonly
used in the measurement of fertilization and thinning trials in
jack pine.
The study area was located near Chapleau, Ontario in a
fire-originated jack pine stand. The stand was treated at age 45
with 336 kg urea-N/ha and a low thinning of 20 percent basal area
in a 2 X 2 factorial design with four replicates.
At stand age 55, 80 trees were felled for stem analysis,
representing 5 tree diameter classes within each stand treatment.
Volume increment, height increment, measures of form, and local
volume equations were determined from the stem analysis data. The
local volume equations were applied to diameter frequency distributions
at stand ages 45, 50, and 55 to calculate stand volumes at
these ages. A growth model was developed to characterize the
annual volume growth of individual trees. The model related the
annual volume growth of an individual tree to its volume, and the
stand volume. Aggregation of the annual volume increments of individual
trees allowed annual stand volume increments to be estimated.
Individual trees responded to fertilization with greater
10-year volume increment and merchantable height increment. On a
stand basis, fertilization resulted in about 20 m[superscript 3] ha[superscript 2] of additional gross volume growth during the ten-year response period,
This volume growth response was greatest in the third and fourth
years after fertilization. Fertilization appeared to have both a
direct effect and an indirect effect. Tlie direct effect was
growth response to the improved nitrogen status, and this effect
ceased 10 years after treatment. The indirect effect was greater
growth due to larger average tree size, and this effect was still
evident 10 years after treatment. Thinning had little effect beyond
salvaging potential mortality.
An examination of methods commonly used to estimate growth
responses to silvicultural treatments was made. The results suggest
that it is necessary to use treatment-specific and age-specific
local volume equations to accurately measure growth response
to fertilization. | |
