Contrasting Litter Nutrient and Metal Inputs and Soil Chemistry among Five Common Eastern North American Tree Species

Abstract

Forest composition has been altered throughout Eastern North America, and changes in species dominance may alter nutrient cycling patterns, influencing nutrient availability and distribution in soils. To assess whether nutrients and metals in litterfall and soil differed among sites influenced by five common Ontario tree species (balsam fir (Abies balsamea (L.) Mill.), eastern hemlock (Tsuga canadensis (L.) Carr.), white pine (Pinus strobus L.), sugar maple (Acer saccharum Marsh.), and yellow birch (Betula alleghaniensis Britt.)), litterfall and soil chemistry were measured at a managed forest in Central Ontario, Canada. Carbon (C) and macronutrient (nitrogen (N), phosphorus (P), potassium (K), calcium (Ca), and magnesium (Mg)) inputs in litterfall varied significantly among sites, primarily due to differences in litterfall mass, which was greatest in deciduous-dominated sites, while differences in elemental concentrations played relatively minor roles. Trace metal inputs in litterfall also varied, with much higher zinc (Zn) and cadmium (Cd) in litterfall within yellow birch dominated stands. Mineral soil oxide composition was very similar among sites, suggesting that differences in soil chemistry were influenced by forest composition rather than parent material. Litter in deciduous-dominated stands had lower C/N, and soils were less acidic than conifer-dominated sites. Deciduous stands also had much shorter elemental residence times in the organic horizons, especially for base cations (Ca, Mg, K) compared with conifer-dominated sites, although total soil nutrient pools were relatively consistent among sites. A change from stands with greater conifer abundance to mixed hardwoods has likely led to more rapid cycling of elements in forests, particularly for base cations. These differences are apparent at small scales (100 m2) in mixed forests that characterize many forested regions in Eastern North America and elsewhere.