Summer Ground Layer Biomass and Nutrient Contribution to Above-ground Litter in an Indiana Temperate Deciduous Forest

Abstract

Eastern deciduous forests of North America have productive ground layers, but information regarding the role of ground layer vegetation in carbon cycling is limited. The ground layer, here defined as all vascular plants ≤1 m in height, contributes most of its biomass and nutrient content annually to the above-ground litter pool. This study assessed the species composition and biomass and nutrient contributions of summer ground layer vegetation to the above-ground litter pool at the AmeriFlux Site in the Morgan-Monroe State Forest, Indiana. Two hundred fifteen 1-m2 subplots were sampled for ground layer species and cover (%). Forty-three of those subplots were harvested for above-ground biomass and tissue nutrient analysis. A 10-cm soil sample was obtained from each harvested subplot and analyzed for pH, organic matter and nutrient content. Boehmeria cylindrica (false nettle), Lindera benzoin (spicebush), Viola spp. (violets), Parthenocissus quinquefolia (Virginia creeper), Polystichum acrostichoides (Christmas fern) and Asplenium spp. (spleenworts) were the most important and abundant ground layer species. Ground layer species were distributed along gradients of weathering and soil organic matter. Mean ground layer cover was 36.7 ± 17.4 % and mean calculated ground layer biomass was 24.7 ± 15.4 g/m2 in the mid- to late-growing season. Ground layer biomass was positively correlated with available soil P. Woody plants accounted for approximately 51% of ground layer biomass followed by non-graminoid herbs (35%) and graminoids (14%). Ground layer litter, comprised of graminoids, non-graminoid herb foliage and stems and woody plant foliage, contributed 26.5 g/m2 and 11.1 g C/m2, or ≤5% of the biomass and C, to the above-ground litter pool in 1999. While the ground layer contributed relatively small quantities of biomass and C to the above-ground litter pool, it provided nutrient-rich tissues with C:N ratios lower than tree leaf litter. With the exception of K, tree leaf litter contributed more nutrients by mass to above-ground litter than did ground layer litter because tree leaf litter comprised 88% of the biomass of above-ground litter.