Modeling long‐term changes in tundra carbon balance following wildfire, climate change, and potential nutrient addition

Abstract

To investigate the underlying mechanisms that control long-term recovery of tundra carbon (C) and nutrients after fire, we employed the Multiple Element Limitation (MEL) model to simulate 200-yr post-fire changes in the biogeochemistry of three sites along a burn severity gradient in response to increases in air temperature, CO concentration, nitrogen (N) deposition, and phosphorus (P) weathering rates. The simulations were conducted for severely burned, moderately burned, and unburned arctic tundra. Our simulations indicated that recovery of C balance after fire was mainly determined by the internal redistribution of nutrients among ecosystem components (controlled by air temperature), rather than the supply of nutrients from external sources (e.g., nitrogen deposition and fixation, phosphorus weathering). Increases in air temperature and atmospheric CO concentration resulted in (1) a net transfer of nutrient from soil organic matter to vegetation and (2) higher C : nutrient ratios in vegetation and soil organic matter. These changes led to gains in vegetation biomass C but net losses in soil organic C stocks. Under a warming climate, nutrients lost in wildfire were difficult to recover because the warming-induced acceleration in nutrient cycles caused further net nutrient loss from the system through leaching. In both burned and unburned tundra, the warming-caused acceleration in nutrient cycles and increases in ecosystem C stocks were eventually constrained by increases in soil C : nutrient ratios, which increased microbial retention of plant-available nutrients in the soil. Accelerated nutrient turnover, loss of C, and increasing soil temperatures will likely result in vegetation changes, which further regulate the long-term biogeochemical succession. Our analysis should help in the assessment of tundra C budgets and of the recovery of biogeochemical function following fire, which is in turn necessary for the maintenance of wildlife habitat and tundra vegetation.

Alleviation of nutrient co‐limitation induces regime shifts in post‐fire community composition and productivity in Arctic tundra

“…Fires remove the insulating soil organic layer resulting in warmer and more deeply thawed soils during succession (Jiang, Rocha, et al, 2015; Rocha & Shaver, 2011b; Rocha et al, 2012). The combustion of vegetation and the soil organic layer also provide new space for species establishment, and alters soil biogeochemistry by reducing C and releasing nutrients that were once tied up in this material (Bret‐Harte et al, 2013; Fetcher et al, 1984; Jiang, Rastetter, et al, 2015; Jiang et al, 2017). The combination of these factors are likely to influence post‐fire community composition and ecosystem structure and function.…”

Post-fire vegetation succession in the Siberian subarctic tundra over 45 years

“…This is unfortunate, as a more comprehensive understanding of fire-plant trait interactions might provide insight into the drivers of changes in ecosystem properties. There is a general need for long-term studies on tundra fire effects (Liljedahl et al , 2007; Jiang et al , 2017), as ecosystem processes in the Arctic are rather slow (Dunbar, 1973; Dahl, 1975). There is also a substantial geographical bias: While almost all studies on tundra fires have been performed in Alaska (e.g.…”

Groundwater Controls on Postfire Permafrost Thaw: Water and Energy Balance Effects

“…Additionally, the severity of the fire varied over the large area burned, providing a gradient of burn severity which can be used to relate the ARF to fires of varying magnitudes elsewhere. Finally, the ARF has been studied in detail due to its proximity to the Toolik Lake Long‐Term Ecological Research field station, providing a rich interdisciplinary body of knowledge to contextualize our study (Bret‐Harte et al, ; De Baets et al, ; Jiang, Rastetter, et al, ; Jiang et al, ; Mack et al, ; Neilson et al, ; Rocha & Shaver, ).…”