# Wildfires in the Siberian Arctic
## 4 Discussion
### Implications for Arctic Ecology and Carbon Storage  
Our analysis of wildfire dynamics in the Siberian Arctic suggests that fire frequency and extent will continue to increase under current climate trends that increase the availability of both above- and below-ground fuel and lightning frequency as a source of ignition. With continued regional warming, the role of lightning as a source of wildfire ignition is likely to increase both because of the increased availability of dry fuel as well as from a direct increase in lightning frequency. Our results show that the relationship of fire to climate is based not just on continuous climate trends, but on \"heat waves\", unusual spikes in air temperature.  
The implications for C dynamics are somewhat less clear. Throughout the Holocene, Arctic taiga and tundra biomes have stored soil C that was removed from the atmosphere and fixed into organic biomass by Arctic vegetation. Although growing seasons are short in the Arctic, conditions that promote microbial decay of soil organic matter are also suppressed to a sufficient degree to result in net accumulation of soil C in deep, wet taiga and tundra soils. The northward migration of the wildfire boundary along with increased fire frequency and extent increases the contribution of greenhouse gases from arctic soils that have accumulated C throughout the Holocene particularly in the carbon-rich soil and turf deposits of the boggy areas of Western Siberia. Increased wildfire has been described as a threat to shift the status of the region from a sink to a source of atmospheric C [16].  
A countervailing trend may be presented for aboveground C storage through enhanced vegetation growth. Since the onset of the current warming period, larch species that dominate in the permafrost zone have increased in growth index, leading to a potential increase in woody biomass [23; 24]. Although quantitative analysis and projections of the balance between fire-driven C loss and vegetation-fixed C accumulation are still poor, these observations support the current status of the Siberian Arctic as a carbon sink [50]. Ouranalyses of the vegetation productivity markers for GPP, NPP, and EVI indicate increased carbon fixation by Siberian Arctic vegetation both within burnt areas (Figure 4) and for the region as a whole (Figures 5 and S1). Similar findings have been reported for boreal forests of North America e.g., [19; 22] who found that net ecosystem biomass production and black spruce growth increased in northern Canada.  
Fundamental changes in vegetation type following wildfire were reported by [PERSON] et al. [51] who found that severe burning of organic soils in Alaskan forests shifted tree dominance from slow-growing black spruce to fast-growing deciduous broadleaf trees, resulting in a net increase in C storage by a factor of five over the disturbance cycle. Tall woody shrubs (e.g., _Alnus frutiosa_) have been reported to replace low-growing herbaceous vegetation after tundra wildfires in western Siberia [52]. Increased dominance of deciduous species in Arctic taiga and tundra could increase the C residence time and mitigate to some extent the release of stored soil C into the atmosphere. Remote sensing of the circumpolar Arctic indicates the phenomenon of \"tundra greening\" in response to more favorable growing conditions supports increased C fixation (e.g., [18; 52]). The same environmental changes in C fixation and storages will be accompanied by changes in the microbial flora that directly affect rates of organic breakdown, so that increased C fixation does not necessarily lead to long-term C storage.  
Although commonly regarded as remote, the circumpolar Arctic is increasingly the focus of modern industrialization, particularly for resource extraction. The implications of increased wildfire, particularly in western Siberia, will pose additional challenges for natural gas and petroleum exploration and utilization.