Three-year height and diameter measurements of Douglas-fir trees were collected from the hoe-forwarding trial near Jordan River in October 2004. Health and vigour of each tree was also assessed in the field. Three-year height and diameter increment was then calculated, and differences between treatments on the trafficked lines were assessed. In addition, growth of Douglas-fir was examined across a range of disturbance types created by the hoe-forwarder. Best height growth of Douglas-fir after three years was found on both the 1-pass puncheon and the 3-pass no-puncheon treatments. Height growth on the puncheon treatments appeared to decrease with increasing number of passes; on the no-puncheon treatments, height growth increased slightly as trafficking by the hoe-forwarder increased. A similar trend was found for diameter growth. Best diameter growth of Douglas-fir after three years was found on the 2- and 3-pass no-puncheon treatments. Diameter growth on the remaining treatments was slightly less, but was similar across all treatments. Results suggest that early performance of Douglas-fir was slightly better on those treatments where disturbance was the greatest. It was anticipated that tree growth would be better on the puncheon treatments where protection of the underlying mineral soil would be provided. However, it is apparent that compression of the thicker forest floor has created more favourable growing sites for Douglas-fir in these early years. A greater amount of residual puncheon on some of the puncheon treatments may also have affected growth response, particularly on those treatments with an increased number of passes by the hoe-forwarder. Growth of Douglas-fir over a range of disturbance types created by the hoe-forwarder was also slightly better where disturbance levels were greatest. Better height and diameter growth were found on the scalped, gouged, and no-puncheon treatments. Poorest growth was found where the thick forest floor remained undisturbed, and on the more compacted areas created by repeated trafficking. However, although growth of Douglas-fir was better on areas of greater disturbance, the incidence of chlorosis in these trees was higher. It appears that nutrient availability and uptake may initially be limited on these disturbances. However, it is expected that once tree roots become established and extend beyond the boundary of the disturbance, the health and vigour of trees growing on scalped and gouged areas will improve. The long-term growth of Douglas-fir in the ruts on the no-puncheon treatment is unknown at this time. Although initial growth was slightly better, localized compacted areas along these ruts may affect future root growth and development. Performance of Douglas-fir in the undisturbed areas was poor. It appears that the thicker forest floors provided less favourable growing sites for these trees. It is expected that differences in tree growth across the various treatments and disturbance types will continue to become more apparent over time. We also expect that some of these early results may change as tree roots grow and into expand adjacent soil. Future measurements will continue to monitor these changes over time, and provide factual input to the FRPA Resource Evaluation Program for soil effectiveness evaluation
Mary- Jane Douglas and Paul J. Courtin.
Douglas, Mary-Jane, Courtin, Paul J.. 2005. Hoe-forwarding impacts on tree growth and site productivity: Jordan River Study Site progress report : three-year results. Forest Investment Account (FIA) - Forest Science Program. Forest Investment Account Report. FIA2005MR031
Topic: FLNRORD Research Program
Keywords: Forest, Investment, Account, (FIA)
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