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,  13C and  15N of plant functional types 17 (PFTs) between burned and unburned ground surfaces soon after a wildfire on a north-18 facing slope in interior Alaska. The C and N were measured for 16 species and 19 Sphagnum litter.  13C differed among the PFTs and was low for trees and shrubs, 20 suggesting that woody stems slowed C dynamics or showed low water use efficiency. 21  15N concentrations suggested that the herbaceous plants depended less on the 22 mycorrhizal associations that became weak on the burned surfaces. The shrub leaves 23 showed the lowest  15N of PFTs and showed higher  15N on the burned surface, showing 24 that N transfer from the soils to the leaves in the shrubs was slowed by the wildfire. 25 Mosses showed the highest C/N ratio. Sphagnum litter decomposed faster on the burned 26 surface, and %N and  15N in the litter increased from the second to third year on both 27 burned and unburned surfaces, while %C changed little. In conclusion, the responses to 28 the wildfire differed among the PFTs as characterized by their C and N dynamics. 2930Key words: Burned and unburned ground surface, carbon (C) and nitrogen (N), Alaskan 31 taiga, plant functional type, stable isotope