Response of foliar nutrients of Rubus allegheniensis to nutrient amendments in a central Appalachian hardwood forest

Foliar nutrient concentrations are often useful in inferring soil fertility and plant-soil interactions. This study examined pre- and post-senescent foliar macronutrients and Mn of Rubus allegheniensis to assess potential effects of two nutrient amendments on mineral soil nutrient availability in aggrading hardwood stands: additions of (NH4)2SO4 (simulating increases in acid deposition) and additions of (NH4)2SO4 with dolomitic limestone (simulating mitigation of effects of acidification). Foliar Mn analysis further addressed a prediction of the nutrient redistribution hypothesis, i.e., Rubus accumulates Mn in pre-senescent leaves and further concentrates Mn in post-senescent leaves to produce high-Mn litter. The study used a four plot × four block randomized design with three experimental treatments (Control, NS, NS + Lime). Rubus leaves were harvested randomly in plots of all treatment before and after senescence. Experimental treatments appeared to increase availability of N and P, with little effect on K. Simulated acidification decreased availability of Ca and Mg, an effect mitigated for Mg by addition of dolomitic limestone. By contrast, Mn in Rubus foliage was up to 100 times more concentrated than in most plant species, and was further concentrated by ∼60% during senescence. These latter observations support predictions of the nutrient redistribution hypothesis that Rubus redistributes Mn from the rooting zone to surface soil.