Effects of nutrient accumulation by aspen, spruce, and pine on soil properties

Nutrient analysis was done for adjacent, 40-year-old stands of pure quaking aspen (Populus tremuloides Michx.), white spruce (Picea glauca Moench Voss), red pine (Pinus resinosa Ait.) and jack pine (Pinus banksiana Lamb.) on two soils in Minnesota to determine the effects of tree species on soil properties. On both soils, aspen and spruce stands accumulated more of most nutrients than did pine stands, and these species differences were reflected in the litterfall. The weight of the forest floor did not differ among species, but nutrient accumulation and pH were greatest under aspen and spruce. Calcium content was about twice as high under aspen and spruce as under the pines. In the mineral soil, phosphorus (P) and potassium (K) did not differ among species; organic matter and nitrogen (N) tended to be lowest under aspen, and calcium (Ca) was much lower under aspen and spruce than under the pines. Soil pH and cation exchange capacity were highest under the pines; this was directly related to soil Ca contents. Mineral soil differences related to species were most pronounced in the top 10 cm; few differences occurred below 25 cm. The large species differences in the N, Ca, and Mg contents of vegetation, forest floor, and mineral soil show a redistribution of these nutrients, but their amounts in the entire ecosystem do not differ by species. In contrast, P and K in the ecosystem decrease in the order aspen\u3espruce\u3epines, and this is largely a reflection of their accumulation in the vegetation since their differences in the soil are minimal