Phosphorus forms and related soil chemistry of Podzolic soils on northern Vancouver Island. II. The effects of clear-cutting and burning

When cedar-hemlock (CH) forests of northern Vancouver Island are clear-cut and replanted, growth of replanted trees is often poor. This growth check can be overcome with nitrogen (N) and phosphorus (P) fertilization, suggesting that it may be because of deficiencies of these elements. A widely used site-preparation tool in these forests is slash burning. Because fire is known to alter nutrient cycling in forests, this burning may be contributing to the problem of poor seedling growth. Thus, the objective of this study was to compare P in forest floor and soils from clear-cut CH stands 10 years, 5 years, and immediately after burning to P concentrations and forms in undisturbed old growth CH stands. Analytical methods included extraction and digestion procedures, fractionation and 31P nuclear magnetic resonance spectroscopy. Soon after burning, an ashbed effect was noted, with increased pH and higher concentrations of available P in surface soil horizons. Available P concentrations and pH returned to pre...