Effects of nitrogen deposition on nitrogen acquisition by Sarracenia purpurea in the Adirondack Mountains, New York, USA

Human generated emissions to the atmosphere have historically increased inorganic nitrogen (N) deposition throughout the Adirondack Mountains of New York. Nitrogen is generally a limiting nutrient for the purple pitcher plant (Sarracenia purpurea L.). Our objective was to determine the dependence of S. purpurea on atmospherically deposited and insect-derived N sources across an increasing nitrogen deposition gradient. Sampling was conducted at 10 sites, with 104 S. purpurea plants sampled. The effects of increasing nitrogen deposition on morphological characteristics and organic N content of S. purpurea and a noncarnivorous reference plant, Chamaedaphne calyculata L. Moench, Leatherleaf, were examined. Sarracenia purpurea flower and C. calyculata leaf tissues were analyzed for stable nitrogen isotope (δ¹⁵N), and foliar N content. Increased nitrogen deposition up to 4.1 kgN∗ha^-1∗yr^-1 was correlated with increased plant size and δ¹⁵N values of S. purpurea. However, deposition exceeding these levels decreased overall plant size and δ¹⁵N values. Nitrogen derived from assimilation of insects ranged from 55% to 90% of foliar N at higher N deposition levels. Plants that acquired the greatest amount of N from insect consumption were also the largest plants. These results reflect the importance of monitoring ecologically sensitive species, like S. purpurea, in light of anthropogenic sources of pollution.