Differences in C, N, δ13C, and δ15N among plant functional types after a wildfire in a black spruce forest, interior Alaska

We measured differences in %C, %N, delta(13C,) and delta N-15 of plant functional types (PFTs) between burned and unburned ground surfaces soon after a wildfire on a north-facing slope in interior Alaska. The C and N were measured for 16 species and Sphagnum litter. delta C-13 differed among the PFTs and was low for trees and shrubs, suggesting that woody stems slowed C dynamics or showed low water use efficiency. delta N-15 concentrations suggested that the herbaceous plants depended less on the mycorrhizal associations that became weak on the burned surfaces. The shrub leaves showed the lowest delta N-15 of PFTs and showed higher delta N-15 on the burned surface, showing that N transfer from the soils to the leaves in the shrubs was slowed by the wildfire. Mosses showed the highest C/N ratio. Sphagnum litter decomposed faster on the burned surface, and %N and delta N-15 in the litter increased from the second to third year on both burned and unburned surfaces, while %C changed little. In conclusion, the responses to the wildfire differed among the PFTs as characterized by their C and N dynamics.