Seasonal storage of carbon, nitrogen, and phosphorus in two perennial forest herbaceous plants

Abstract

Herbaceous perennials in a forest ecosystem play a role in seasonal nutrient cycling. Asarum canadense L. (wild ginger) and Hydrophyllum virginianum L. (Virginia waterleaf) are perennial herbaceous plants with different seasonal growth patterns native to mesic hardwood forests. Both flower early, but A. canadense leaves persist after flowering while H. virginianum senesces and produces a second flush of leaves by late summer. Our specific question of interest was whether there is a difference in nutrient storage in leaves and roots seasonally in these two species. We excavated plants in spring, summer, and fall to determine carbon (C), nitrogen (N), and phosphorus (P) concentration and content in above and below ground tissues, as well as C:N and N:P ratios. Our findings indicate complex patterns in the location of nutrients in A. canadense and H. virginianum across the growing season. Asarum canadense exhibits relatively consistent above ground growth, with seasonal nutrient accumulation focused below ground for C, N, and P. Patterns are more varied in H. virginianum as a result of the second flush of leaves, notably, the C:N ratio of H. virginianum decreases across the growing season while the N:P ratio increases, but to different degrees in above/below ground tissues. We suggest these patterns are linked to changing photosynthetic capacity across the seasons and a prioritization of vegetative growth over reproductive investment.