As the Arctic warms, tundra wildfires are expected to become more frequent and severe. Assessing how the most flammable regions of the tundra respond to burning can inform us about how the rest of the Arctic may be affected by climate change. Here we describe ecosystem responses to tundra fires in the Noatak River watershed of northwest Alaska using shrub dendrochronology, active-layer depth monitoring, and remotely sensed vegetation productivity. Results show that relatively productive tundra is more likely to experience fires and burn more severely, suggesting that fuel loads currently limit tundra fire distribution in the Noatak Valley. Within three years of burning, most alder shrubs sampled had either germinated or re-sprouted, and vegetation productivity inside sixty burn perimeters recovered to pre-fire values. Tundra fires resulted in two phases of increased primary productivity as manifested by increased landscape greening. Phase one occurred in most burned areas 3-10 years after fires, and phase two occurred 16-44 years after fire in situations where tundra fires triggered near-surface permafrost thaw resulting in shrub proliferation. A fire-shrub-greening positive feedback is currently operating in the Noatak Valley and this feedback could expand North as air temperatures, fire frequencies, and permafrost degradation increase. This feedback will not have indiscriminate expansion though; in the Noatak Valley, the fire-shrub-greening process is relatively limited in tussock tundra, where low-severity fires and shallow active layers exclude shrub proliferation. Climate warming and enhanced fire occurrence will likely shift fire-poor regions into either the tussock tundra or erect shrub tundra fire-adapted ecological attractor states that now dominate the fire-rich Noatak Valley.
|Date made available||Jan 1 2021|
|Publisher||UC Santa Barbara|