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

Abstract

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 pine (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 lowest element contents of all species. Differences in forest floor C/nutrient ratios, pH, and element contents between sites of low nutrient 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.