LAUSR

Previous meta-analyses suggested that carnivorous plants - despite access to N, P, and K from prey - have significantly lower leaf concentrations of these nutrients than non-carnivores. Those studies, however, largely compared carnivores in nutrient-poor habitats with non-carnivores in more nutrient-rich sites, so that the differences reported might reflect habitat differences as much as differences in nutrient-capture strategy. Here we examine three carnivorous and 12 noncarnivorous plants in the same nutrient-poor bog to compare their foliar nutrient concentrations, assess their patterns of nutrient limitation using leaf NPK stoichiometry, and estimate %N derived from prey by carnivores using a mixing model for stable N isotopes. We hypothesized that (1) carnivore leaf nutrient concentrations approach or exceed those of non-carnivores in the same nutrient-poor habitat; (2) species in different functional groups show different patterns of stoichiometry and apparent nutrient limitation; and (3) non-carnivores might show evidence of employing other means of nutrient acquisition or conservation to reduce nutrient limitation. At Fallison Bog in northern Wisconsin, carnivorous plants (Drosera rotundifolia, Sarracenia purpurea, Utricularia macrorhiza) showed significantly lower leaf % C and N:P ratio, higher δ15 N, and no difference from non-carnivores in leaf N, P, K, and δ13 C. Sedges had significantly lower leaf % P, % C, and N:K ratio, and higher K:P ratio than non-sedges restricted to the Sphagnum mat, and may tap peat N via aerenchyma-facilitated peat oxidation (oxipeditrophy). Evergreen ericaceous shrubs exhibited significantly higher levels of % C and lower values of δ15 N than mat non-ericads. Calla palustris - growing in the nutrient-rich moat at the bog's upland edge - had very high values of leaf N, K, δ15 N, and N:P ratio, suggesting that it may obtain nutrients from minerotrophic flows from the adjacent uplands and/or rapidly decaying peat. Stoichiometric analyses indicated that most species are N-limited. A mixing model applied to δ15 N values for carnivores, non-carnivores, and insects produced an estimate of 50% of leaf N derived from prey for Utricularia, 42% for Sarracenia, and 41% for Drosera.