Declining root strength in Douglas-fir after felling as a factor in slope stability
Burroughs, E.R., Jr.; Thomas, B.R. 1977.
Declining root strength in Douglas-fir after felling as a factor in slope stability.
Research Paper INT-190. USDA Forest Service.
Intermountain Forest and Range Experiment Station. 27 p.
Keywords: root strength, slope stability
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Abstract:
Numbers of roots per unit area of soil and the individual
root tensile strength for two varieties of Douglas-fir --
Coast fir (Pseudotsuga menziesii) in western Oregon and
Rocky Mountain fir (var. glauca) in central Idaho --
decreased rapidly with time after felling.
Seventy-five percent of the Douglas-fir roots 1 cm or smaller in diameter
were lost within 24 months after felling in the coastal variety,
and within 60 months after felling in the Rocky Mountain variety.
Numbers of roots per unit area of soil were combined with tensile
strength of individual roots to estimate total tensile strength per unit
area of soil.
Total tensile strength declined from about 1,700 kg/m2
to about 230 kg/m2 within the first 30 months after felling for roots
1 cm and smaller of the Coast Douglas-fir.
Total tensile strength
declined from about 850 kg/m2 to about 300 kg/m2 for the same time
period and root size class of the Rocky Mountain Douglas-fir.
Coast Douglas-fir roots are stronger than those of the Rocky Mountain
variety, but decay faster.
Live strength is a characteristic of the
variety of fir, but differences in decay rates are probably a function
of climate.
Moscow FSL publication no. 1977a
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