Supplementary material from "Resilience of lake biogeochemistry to boreal-forest wildfires during the late Holocene"

• Main Authors: Chipman, Melissa L., Hu, Feng Sheng
• Format: Article in Journal/Newspaper
• Language: unknown
• Published: The Royal Society 2019
• Subjects: Environmental Science; Ecology; FOS Biological sciences; New Lake; permafrost; Alaska
• Online Access: https://dx.doi.org/10.6084/m9.figshare.c.4614500; https://rs.figshare.com/collections/Supplementary_material_from_Resilience_of_lake_biogeochemistry_to_boreal-forest_wildfires_during_the_late_Holocene_/4614500

Novel fire regimes are expected in many boreal regions, and it is unclear how biogeochemical cycles will respond. We leverage fire and vegetation records from a highly flammable ecoregion in Alaska and present new lake-sediment analyses to examine biogeochemical responses to fire over the past 5300 years. No significant difference exists in δ 13 C, %C, %N, C : N, or magnetic susceptibility between pre-fire, post-fire and fire samples. However, δ 15 N is related to the timing relative to fire ( χ 2 = 19.73, p 15N increased gradually from 1.8 ± 0.6 to 3.2 ± 0.2‰ over the late Holocene, probably as a result of terrestrial-ecosystem development. Elevated δ 15 N in fire decades likely reflects enhanced terrestrial nitrification and/or deeper permafrost thaw depths immediately following fire. Similar δ 15 N values before and after fire decades suggest that N cycling in this lowland-boreal watershed was resilient to fire disturbance. However, this resilience may diminish as boreal ecosystems approach climate-driven thresholds of vegetation structure, permafrost thaw and fire.