Forest Investment Account

Abstract of FII Project R02-46

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Hoe-forwarding Impacts on Tree Growth: Jordan River study site - progress report - one-year results

Author(s): Douglas, Mary-Jane; Courtin, Paul J.
Imprint: Houston, B.C. : Houston Forest Products Ltd., 2003
Subject: Pseudotsuga Menziesii, British Columbia, Growth, Soil Fertility, Soils, Density
Series: Forest Investment Account (FIA) - Forest Science Program


An assessment of soil density was carried out on the third hoe-forwarding site installed near Jordan River during the summer of 2002. Soils were sampled to determine differences in soil density between a range of disturbance types, along the trafficked lines, and from undisturbed areas identified throughout each block. Estimates of soil mechanical resistance were also obtained for each of the points where soil bulk density samples were collected. Soil moisture was determined at each of these points using a Theta probe. First-year height and diameter measurements of Douglas-fir seedlings were also collected, and seedling condition noted. Results showed slightly higher soil bulk densities where the site had been trafficked. However these differences were not found to be significant even though field observations noted differences between the disturbance types. It may be that assessment of soil bulk density on forested sites is less sensitive due to sample variability or to some extent, sampling error. However, soil density values obtained for this site represent soil conditions where there is little to no restriction for root growth and development. Soil mechanical resistance values were also higher where the site had been trafficked. However, these mean values represent soil conditions where there was little restriction to root growth. The exception was the very deep rut (VDR) created where puncheon was used. Although this represented only one value, it was close to the point that is considered a restriction to root growth, i.e., 2500 kPa. Other individual values throughout the blocks also had values that were close to or in excess of the maximum resistance value. Results showed little difference in either height or diameter increment across the various disturbance types after one growing season. We expect that differences will become more apparent over time as the roots extend into the surrounding soil. Therefore tree growth should continue to be monitored over the longer-term.
Mary-Jane Douglas and Paul J. Courtin.

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Updated August 02, 2006 

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