Phosphorus forms and related soil chemistry of Podzolic soils on northern Vancouver Island. I. A comparison of two forest types

When cedar-hemlock (CH) and hemlock - amabalis fir (HA) forests of northern Vancouver Island are clearcut and replanted, growth of replanted trees is often poor on CH clearcuts but not adjacent HA clearcuts. This poor growth can be overcome with nitrogen (N) and phosphorus (P) fertilization, which s uggests differences in nutrient cycling between CH and HA forests. The obje ctive of this study was to investigate soil P in mature, uncut stands of CH and HA forests. The results suggest that there are no inherent differences in soil P concentration between the CH and HA forests. The diversity of P forms as revealed by P-31-NMR spectroscopy was typical of cool, moist acidi c forests with high P immobilization. Diester phosphates were found through out the soil profile, albeit at very low levels in the mineral horizons. Ph osphorus forms and cycling were vertically stratified down the profile. Mos t of the P in the LF horizon was in organic forms typical of litterfall. In the more humified H horizon the P forms were more typical of soil organism s. The high C/N and C/P ratios in the LF and H horizons at the CH site are consistent with microbial immobilization. In the upper Bhf horizon, inorgan ic P was predominantly nonoccluded. Organic P was present, mainly as orthop hosphate monoesters, which were probably adsorbed on soil colloids. In the lower Bhf horizon, most P was occluded in amorphous sesquioxides, with low levels of organic P, mainly as orthophosphate monoesters.