Transcript WholeTreeHarvestPackForest

EFFECT OF HARVEST REMOVAL ON PRODUCTIVITY OF A 15-YEAR-OLD DOUGLAS-FIR
PLANTATION.
by Dale W. Cole and Jana E. Compton
University of Washington and Harvard Forest
ABSTRACT
In 1979 a study was established in western Washington to examine the effect of harvest
removal on second-rotation Douglas-fir productivity. Three levels of removal were
included: bole only, whole-tree (above-ground), and whole-tree plus forest floor. The
study was established in adjacent areas of low and medium site quality (24 vs. 34 m site
index at 50 years for Douglas-fir). After 5 years, 224 kg urea N ha-1 was applied to one
of the paired plots within each of the harvest removal treatments. Height growth
records after 15 years indicate that for the low quality site, there is a consistent
relationship between the amount of harvest removal and the reduction of height and
diameter growth of the second-rotation plantations. Mean tree height on the completeremoval plot was 26% less than that on the bole-only plot with a similar reduction in
mean diameters. However, this same growth reduction was not noted at the higher
productivity site. Fertilization resulted in an increase in growth and largely restored the
decrease in production caused by harvest removal. We conclude that the low quality
site forest was N deficient and harvest removal further aggravated this deficiency
Table 1. Biomass and nitrogen contained within each ecosystem component
prior to harvest, and the removal of biomass and nutrients through harvest.
(from Compton and Cole 1990).
Table 1. Biomass and nitrogen contained within each ecosystem component
prior to harvest, and the removal of biomass and nutrients through harvest.
(from Compton and Cole 1990).
Table 2. Additional leaching of N, primarily as nitrate, past the 50-cm soil
depth during the first year following harvesting (from Bigger and Cole,
1983). Net leaching losses were calculated by subtracting losses in the
forested control from those in the treatment plots.
Table 3. Total loss of N by harvest removal and leaching following boleonly, whole-tree, and complete-removal.
Table 4. Average height (standard deviation) of seedlings on each plot, 15 years
after harvest; significant differences are indicated with letters: “a” signifies the
smallest average height (p<0.05; statistical comparisons were made between all
treatment plots using Tukey’s HSD).