Open Collections

Effects of spacing on multi-aged interior douglas-fir stands in central British Columbia

University of British Columbia

Re-measurement data over a period of four years from 24 permanent plots were analyzed to determine the effects of three different spacing regimes on growth of uneven-aged interior Douglas-fir (Pseudotsuga menziesii var. glauca), near Williams Lake, British Columbia. Spacing was carried out during the fall and winter of 1990-1991. Growth was analyzed at the stand and individual tree level between the beginning of the 1993 growing season and the end of the 1996 growing season. Variables of interest at the stand level were growth and growth rate of quadratic mean diameter, basal area per hectare, Lorey's height, volume per hectare and accumulated crown area per hectare. Variables of interest for individual trees were growth in diameter, basal area, total height, total stem volume, crown area and live crown length. Analysis of variance was used to judge the significance of treatment effects. At the stand level, there were no significant differences among treatments for any of the variables. However, treatment means of quadratic mean diameter, basal area, volume, and accumulated crown area were consistently lower in the control plots than in the spaced plots. In the spaced plots, the 5 m clumped spacing showed consistently higher growth rates in relative terms. Stand diameter growth was 0.37 cm on the control, and ranged from 0.80 to 1.08 cm on the spaced plots. Net basal area growth averaged 2.34 m²/ha on the control, and 3.23 to 3.52 m²/ha on the spaced plots, while mortality represented 0.83 m²/ha on the control, and 0.01 to 0.22 m²/ha on the spaced plots. Spacing did not reduce net periodic annual volume increment which was 4.8 m³/ha on the control, and 5.2 to 6.6 m³/ha on the spaced plots. At the individual tree level, small Douglas-fir tree (<15 cm dbh) growth responses significantly differed between control and spacing treatments for diameter, basal area, height, and volume. Large Douglas-fir tree (>15 cm dbh) diameter and basal area growth response differed significantly between the control and the 5 m clumped spacing. Despite similar trends, results were less distinct for non- Douglas-fir species. Up to 20-25 cm dbh, volume growth efficiency increased regularly with increasing dbh on both control and spaced plots. Trees seemed to be the most efficient for the 5 m clumped spacing and the least efficient for the control. The study also showed that age distribution was clearly distinct from diameter distribution.

Thesis/Dissertation

application/pdf

2009-06-09

For non-commercial purposes only, such as research, private study and education. Additional conditions apply, see Terms of Use https://open.library.ubc.ca/terms_of_use.

http://hdl.handle.net/2429/8896

Forestry

University of British Columbia

UBCV

DSpace