NUTRIENT CONTENT OF FOREST SHRUBS FOLLOWING BURNING

Abstract

Prescribed burning under mature Larch/Douglas‐fir forests produced changes in elemental uptake. Elemental analyses of individual species and existing biomass three years post‐burn from hot, medium, and lightly burned sites and unburned controls showed a significant shift in species composition with burn intensity. Few species from hotly burned sites had elevated levels of ions, except phosphorus and iron, but the aboveground shrub and herb biomass did have greater total cations, percent ash, and individual cations (except Ca and Mg) on hotly burned sites. Although the hotly burned sites had the greatest total biomass, only iron, manganese, total nitrogen, sodium, and phosphorus were significantly higher (5% level) in biomass from hot burns compared to control biomass (g/m 2 basis). Hot burns alter the soil pH to the alkaline range making some elements like iron less soluble and available. Some species growing on hotly burned sites appeared able to alter nutrient uptake making more iron, phosphorus, and other elements available for growth, even with low available levels, compared to control sites. Three‐year‐old western larch ( Larix occidentalis Nutt.) seedlings were able to accumulate high levels of Fe, K, and P relative to controls. Marchantia polymorpha L. concentrated some ions on hotly burned soils, but it was not possible to locate this plant on unburned areas for comparison.