Fire in lichen-rich subarctic tundra changes carbon and nitrogen cycling between ecosystem compartments but has minor effects on stocks

Abstract

Abstract. Fires are predicted to increase in Arctic regions due to ongoing climate change. Tundra fires can alter carbon and nutrient cycling and release a substantial quantity of greenhouse gases with global consequences. Yet, the long-term effects of tundra fires on carbon (C) and nitrogen (N) stocks and cycling are still unclear. Here we used a space-for-time approach to investigate the long-term fire effects on C and N stocks and cycling in soil and aboveground living biomass. We collected data from three large fire scars (>44, 28, and 12 years old) and corresponding control areas and used linear mixed-effect models in a Bayesian framework to analyse long-term development of C and N stocks and cycling after fire. We found that tundra fires had no long-term effect on total C and N stocks because a major part of the stocks was located belowground in soils which were largely unaltered by fire. However, fire had a strong long-term effect on stocks in the aboveground vegetation, mainly due to the reduction in the lichen layer. Fire reduced N concentrations in graminoids and herbs on the younger fire scars, which affected respective C/N ratios and may indicate an increased post-fire competition between vascular plants. Aboveground plant biomass was depleted in 13C in all three fire scars. In soil, the relative abundance of 13C changed with time after fire. Our results indicate that in lichen-rich subarctic tundra ecosystems, the contribution of fires to the release of additional carbon to the atmosphere might be relatively small as soil stocks appear to be resilient within the observed time frame.

The Arctic Plant Aboveground Biomass Synthesis Dataset

“…87 Russia 68.88 161.44 117 2012–2013 Heim, et al . 25 Russia 67.01 79.14 58 2017–2018 Loranty and Natali 88 Russia 69.32 161.56 26 2014 Mikola, et al . 89 Russia 71.59 128.89 92 2014 Siewert, et al .…”

“…Rather, plant biomass typically has been measured as part of individual research projects, each with its own focus and protocols. For instance, researchers have investigated how plant biomass is affected by climate 23 , 24 , wildfire 25 – 28 , herbivores 29 , 30 , and soil properties such as texture, nutrients, and pH 31 – 33 . Researchers have also measured plant biomass to assess ecosystem carbon storage 34 , 35 , evaluate terrestrial ecosystem models 36 , and map spatial patterns of plant biomass from landscape to biome scales by linking field and remote sensing measurements 37 – 40 .…”