Nutrient resorption efficiency and proficiency in fronds and trophopods of a winter-deciduous fern, Dennstaedtia punctilobula

We measured resorption of nitrogen (N), phosphorus (P), copper (Cu), manganese (Mn), and zinc (Zn) in the fronds and trophopods of 12 populations of a winter-deciduous fern, Dennstaedtia punctilobula, because (1) resorption (the withdrawal of nutrients from senescing tissues) has been measured in only one other winter-deciduous fern and one wintergreen fern, (2) the majority of what is known about resorption is derived from studies of woody plants, and (3) the architecture and life history of ferns differ fundamentally from woody perennials in ways that could significantly impact resorption. Resorption of N and P from fronds was both efficient (52% N, 50% P; percentage of nutrient in green leaves withdrawn during senescence) and proficient (0.7% N, 0.07% P; concentration of nutrient in fully senesced leaves). Copper was resorbed from fronds (17% resorption efficiency), but Mn and Zn were not. Rhizomes were a significant sink for resorbed N and P, but trophopods (enlargements of the petiole thought to function as storage organs) were neither a source nor a sink for resorbed nutrients. In comparisons with other herbaceous life-forms of plants, resorption of N and P in ferns was similar in efficiency to that in graminoids and forbs but dissimilar in proficiency to that in forbs. Therefore, while these data support the tenet that resorption efficiency does not differ among life-forms, they also reveal apparent fundamental differences in resorption proficiency among life-form classes of plants.