Mechanized Thinning, Prescribed Fire, and Needle Age Influences on the Mineral Nutrition of Jeffrey Pine: Elemental Concentrations in Foliage and Soil

Forest thinnings using cut-to-length and whole-tree harvesting approaches followed by prescription underburning were assessed for their influences over multiple growing seasons on the mineral nutrition of Jeffrey pine (Pinus jeffreyi Grev. & Balf.) on a Sierran site. Specifically examined were foliar and soil elemental concentrations encompassing macronutrients and micronutrients plus Al. Foliar N was higher in thinned stand subunits initially before transitioning to a relatively elevated concentration in the burned portion of either the cut-to-length or wholetree subunits, while higher foliar S in the burned cut-to-length treatment combination was evident in the last two of the six sampling periods. Foliar Mn was usually higher in the burned whole-tree combination while B and Al were often higher in burned stand portions but with less specificity regarding thinning treatment. At mid growing season, N, P, K, S, Fe, and Cu were higher in young needles while Ca, Mn, and Al were so in older ones. Near mid study, mineral soil Ca was higher in the unthinned subunit while Mg, Fe, Mn, Zn, and Cu were higher in unburned stand portions.