Data for: "Limitations of a frozen feast: Light availability affects boreal plant access to novel nitrogen released from permafrost thaw"

Climate change is driving permafrost thaw, releasing previously frozen resources, such as nitrogen, to the soil active layer. In low-nitrogen systems, like boreal peatlands, this novel nitrogen source may benefit plant productivity. However, other resource limitations (e.g., light) may limit plant access to thaw-front nitrogen. We used a stable isotope experiment to explore variations in understory boreal plant species’ ability to take up different forms of newly released nitrogen from permafrost thaw under different canopy covers. This experiment occurred in a peatland in the sporadic discontinuous permafrost zone of the Northwest Territories, Canada. We added 15N labelled ammonium, nitrate, and the amino acid glycine at the thaw front (40 cm depth) at two sites differentiated by high and low canopy cover and determined uptake of 15N in leaves of several common and abundant boreal plant species. At each site we had 6 quadrats that were 2 m by 2 m and applied one of the four treatments (control (no addition), glycine, ammonium, nitrate) in each corner. This data set provides nitrogen permil values, percent nitrogen, and foliage dry weight analyzed for nitrogen. Foliage was collected one year after 15N addition. We found that the probability of plant uptake of thaw-front nitrogen was significantly greater at low canopy cover sites; however, nitrogen form, plant species, and foliar Nmass had no effect. We further found that Rubus chamaemorus had the highest foliar Nmass followed by Rhododendron groenlandicum, Chamaedaphne calyculata, and Vaccinium vitis-idea. Our results demonstrate that access to nitrogen released from permafrost thaw by boreal plants may be mediated by light availability. Understanding the variation in site response to permafrost thaw contributes to our understanding of how boreal peatlands will change with ongoing climate change.