Forest floor chemistry under seven tree species along a soil fertility gradient

Forest floor chemistry, i.e., C/nutrient ratios, pH, and element contents, were determined in stands of two deciduous species and five conifer species replicated at seven sites along a soil fertility gradient. There were consistent differences between forest floors of the tree species. Lodgepole Fine (Pinus contorta Dougl.) forest floors had highest C/nutrient ratios, lowest pH, and the greatest element contents, whereas oak (Quercus robur L.) forest floors had low C/nutrient ratios and the fewest element contents of all species. Differences in forest floor C/nutrient ratios, pH, and element contents between sites of low nun-lent status and sites of intermediate to high nutrient status were also great. Forest floor pH was related to mineral soil pH, and C/P, C/Ca, and C/K ratios were related to mineral soil nutrient concentrations. Forest floor C content was negatively related to most mineral soil fertility variables and was closest related to texture, pH, and concentrations of P and Ca. The C content of lodgepole pine and oak forest floors tended to be less affected by the soil fertility gradient. The results suggest that C storage and immobilization of nutrients in forest floors may be managed along an extensive soil gradient by selection of the proper tree species.