A study was initiated in 1986 near Salvus in the Kalum Forest District to determine the effects of silvicultural treatments for the conversion of red alder stands growing on coastal alluvial sites to conifer plantations. One objective of the study was to assess the impact of these treatments on soil properties related to site productivity. Soil samples were taken for chemical analysis and for the determination of bulk density before the application of treatments (1986), one year after treatments (1988), and five years after treatments (1992). The sandy-textured soils at Salvus give it a low compaction hazard rating. Consistent with that, the upper 15-cm layer showed no adverse changes as a result of any of the silvicultural treatments either in 1988 or 1992. It is important to note. however, that on more sensitive sites with finer soil textures and/or on greater slopes. similar blading treatments will result in highly detrimental compaction and surface erosion. Interestingly, density within the 15-30-cm layer increased markedly between 1988 and 1992, with the largest increases observed in the undisturbed standing alder control plots. It is possible that changes in water table levels between 1988 and 1992 and differences in soil climate and vegetation between treated and control plots may be affecting earthworm activity, and indirectly, soil porosity and density. The concentrations of some nutrients (available phosphorus (P), extractable calcium (Ca), magnesium (Mg), and potassium (K)) and soil pH fluctuated significantly from year to year in the undisturbed control plots. While these changes were observed for nutrients in 'available' forms, total nitrogen (N), which occurs primarily in less mobile organic forms, remained relatively stable in the controls from year to year, particularly in the 0-15-cm layer. This suggests the involvement and probable importance on this site of nutrient-rich seepage water. Blading, and blading in combination with seeding with grass and clover resulted in reductions in N, K, and P that were substantial and greater than those observed for any of the other treatments. By 1992, available P and K were still low relative to pre-treatment levels. Total N concentrations had, however, returned to pre-treatment levels in the bladed plots but not in the bladed/seeded plots. Of the silvicultural treatments, burning appeared to have relatively benign effects on soil properties, particularly compared to blading and blading/seeding treatments. There is some evidence of higher concentrations of available K and possibly also P relative to controls in response to burning, probably as a result of the deposition of ash on the soil surface.
A. Macadam, B.A. B!ackwell. 1994. Conversion of Multistoried Brush Fields to Coniferous Plantations - Progress Report for Treatment Effects on Soils: Results of Fifth Year Post-Treatment Sampling. FLNRORD
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