Epsilon Archive for Student Projects

Abstract

This study a is continuation of the long-term experiment established by Šaicāne
(2019). The main aim of the study was to examine the initial effect of different
thinning regimes on growth of Silver birch (Betula pendula Roth) planted on
abandoned farmlands in Latvia. The experimental design consisted of 6 different
thinning treatments, varying in thinning intensity from 33.3% (800 trees ha-1 being
left after first thinning) to 66.7% (400 trees ha-1 left after the first thinning). The
long-term experiment as initially planned by Šaicāne (2019) will require a
continuous implementation of the different thinning regimes intended for each
treatment, including a different rotation length across the treatments – from 30 to
45 years. However, in this study, only the initial effect of the first thinning was
evaluated and presented.
The two main objectives derived from the main aim of this study was to evaluate
both growth of individual Silver birch trees as well as and the production as a whole.
The collected data was used to estimate and evaluate different stand describing
variables such as basal area, volume, basal area weighted height and diameter.
Various functions were applied to estimate height, basal area, and volume.
Ultimately, a statistical model was constructed to test effect of different thinning
treatments on growth of Silver birch.
Positive corelation was found between thinning intensity and diameter growth,
with most heavy thinning showing the highest growth and the untinned Control the
lowest. Moreover, it was shown, that the largest trees in each treatment also
exhibited the highest diameter growth. Differences between 1st quartile (smallest)
and 4th quartile (largest) were 14 – 25% for thinned plots and 148% for the untinned
Control. Height growth had no statistically significant deviation across the
treatments and sites. Basal area growth negatively corelated with thinning intensity,
i.e., best growth was achieved by the light intensity thinning and the poorest growth
by the high intensity thinning. Volume production was highest in lowest intensity
treatment – 15 m3, followed closely by Control with 14 m3. Lowest volume
production was in most intensive thinning 9.6 m3.