The influence of soil compaction on early conifer growth in the southern Washington Cascades Public Deposited

http://ir.library.oregonstate.edu/concern/graduate_thesis_or_dissertations/ht24wn02w

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  • This study evaluated the effect of soil compaction on the growth of natural regeneration on volcanic ash-influenced soils in the southern Washington Cascades. Growth of 9 to 18 year-old sapling-. sized Ponderosa pine (Pinus ponderosa Laws.) was studied on sites ranging from 915 to 1006 m elevation in an area selectively logged in 1959, and for 10 to 13 year-old lodgepole pine (Pinus contorta Dougl.) established following a group selection harvest on a 1342 in elevation site logged in 1967. Soils ranged from loam to sandy loam texture. Height, diameter, and volume growth were measured for trees growing under an array of disturbance conditions to determine the influence of soil compaction on their size and growth rates. A number of soil, vegetation, and site variables were studied to determine possible cause and effect relationships with growth parameters. Bulk density of the surface 30.5 cm was measured within the lateral rooting zone to provide an index of compaction. Trees were destructively sampled to obtain a detailed record of their development, and to adjust for differences in age as a result of variable establishment delays. Average bulk density increases of 15.4 and 27.5 percent relative to adjacent undisturbed soil were found for skid trails in the ponderosa pine and lodgepole pine study areas, respectively. The effect of soil displacement overshadowed any possible relationship between bulk density and growth for lodgepole pine. The strong correlation of growth with organic matter content indicates that removal of nutrient-rich surface soil during logging and slash disposal operations may significantly affect site productivity, particularly for poorly developed skeletal soils. Regression analysis showed that several growth parameters for ponderosa p1ne were strongly associated with the increase in bulk density despite additional significant relationships with tree age, site index, and overstory cover. Reductions in total growth of 4.8, 7.7 and 20.4 percent were predicted for height, diameter, and stem volume of 14 year-old skid trail regeneration based on the mean bulk density increase. Evaluation of current growth increment was effective in adjusting for differences in tree age. Predicted average reductions in height, diameter, and volume growth of 7.1, 11.8, and 18.9 percent were estimated for young ponderosa pine based on the last five year period. Projected impacts from regression analysis represent conservative estimates, since the mean density increase used is the prediction model included measurements for sample trees growing in soil with bulk densities comparable to undisturbed levels. When the ponderosa pine sample was stratified into low and high impact groups based on bulk density increases, differences in the shape of height-age and diameter-age curves were apparent. A significant decrease in the rate of growth was noted for trees growing under highly disturbed conditions. Projected effects of compaction on site productivity throughout the rotation are difficult to assess, but measurable reductions in young tree growth coupled with frequent stand entries and the slow rate of natural soil recovery provide a basis for concern for long-term impacts.
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  • description.provenance : Approved for entry into archive by Linda Kathman(linda.kathman@oregonstate.edu) on 2008-11-17T17:13:35Z (GMT) No. of bitstreams: 1 Robbins, Richard W_1983_MS.pdf: 750143 bytes, checksum: 43d0e3cb24063e0523f645a4d833de69 (MD5)
  • description.provenance : Approved for entry into archive by Linda Kathman(linda.kathman@oregonstate.edu) on 2008-11-17T17:19:49Z (GMT) No. of bitstreams: 1 Robbins, Richard W_1983_MS.pdf: 750143 bytes, checksum: 43d0e3cb24063e0523f645a4d833de69 (MD5)
  • description.provenance : Made available in DSpace on 2008-11-17T17:19:50Z (GMT). No. of bitstreams: 1 Robbins, Richard W_1983_MS.pdf: 750143 bytes, checksum: 43d0e3cb24063e0523f645a4d833de69 (MD5)
  • description.provenance : Submitted by Savanna Bidwell (sbscanner@gmail.com) on 2008-10-29T21:59:34Z No. of bitstreams: 1 Robbins, Richard W_1983_MS.pdf: 750143 bytes, checksum: 43d0e3cb24063e0523f645a4d833de69 (MD5)

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