Differences in C, N,δ13C, andδ15N among plant functional types after a wildfire in a black spruce forest, interior Alaska

Abstract

We measured differences in %C, %N, δ13C, and δ15N 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. δ13C differed among the PFTs and was low for trees and shrubs, suggesting that woody stems slowed C dynamics or showed low water use efficiency. δ15N 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 δ15N of PFTs and showed higher δ15N 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 δ15N 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.