People in the Arctic face uncertainty in their daily lives as they contend with environmental changes at a range of scales from local to global. Freshwater is a critical resource to people, and although water resource indicators have been developed that operate from regional to global scales and for midlatitude to equatorial environments, no appropriate index exists for assessing the vulnerability of Arctic communities to changing water resources at the local scale. The Arctic Water Resource Vulnerability Index (AWRVI) is proposed as a tool that Arctic communities can use to assess their relative vulnerability-resilience to changes in their water resources from a variety of biophysical and socioeconomic processes. The AWRVI is based on a social-ecological systems perspective that includes physical and social indicators of change and is demonstrated in three case study communities/watersheds in Alaska. These results highlight the value of communities engaging in the process of using the AWRVI and the diagnostic capability of examining the suite of constituent physical and social scores rather than the total AWRVI score alone.

The Kougarok area, situated on the central Seward Peninsula, Alaska, experienced a severe fire in August 2002. This may be the only tundra fire where high‐quality prefire (1999–2002) and postfire (2003–2006) active layer and meteorology measurements have been collected in the same locations. After fire, near‐surface soil showed increased moisture at the burned tussock site, remaining close to saturation throughout the thawed season 2003–2006. Despite wetter soil after the fire, freezing occurred earlier at the burned tussock site than at the control, indicating the importance of a reduced organic layer. Severe combustion of lichen and moss left 15–25 cm high tussocks, resulting in a doubling of the surface roughness coefficient. Average September temperature at the tussock site increased 2.3 ± 0.7°C throughout the 1 m soil profile, doubling the active layer depth, although this is due partly to favorable meteorological conditions. The shrubby control station experienced a mean annual temperature increase of 1.1 ± 0.3°C in the upper 0.5 m. A similar annual change was found at the burned tussock site. Cooler weather conditions in 2006 stagnated the soil‐warming trend, which occurred after 2002. How the thermal and moisture regimes in tundra will be affected after fire is highly influenced by weather, fire severity, vegetation regrowth, prefire vegetation, and ground ice conditions.

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An open black spruce forest, the most common ecosystem in interior Alaska, is characterized by patchy canopy gaps where the forest understory is exposed. This study measured CO2, sensible heat, and latent heat fluxes with eddy covariance (EC) in one of those large canopy gaps, and estimated understory fluxes in a black spruce forest in 2011-2014. Then understory fluxes and ecosystem fluxes were compared. The understory fluxes during the snow-free seasons were determined by two approaches. The first approach determined understory fluxes as the fluxes from the canopy gap, assuming that fluxes under the canopy crown also had the same magnitude as the canopy gap fluxes. The second approach determined the understory fluxes by scaling canopy gap fluxes with a canopy gap fraction, assuming that only canopy gaps, which mostly constitutes the forest floor, contribute to fluxes. The true understory fluxes would be in between these two estimates. Overall, the understory accounted for 53 (39-66) %, 61 (45-77) %, 63 (45-80) %, 73 (56-90) %, and 79 (59-98) % of the total net ecosystem productivity (NEP), gross primary productivity (GPP), ecosystem respiration (RE), sensible heat flux (H), and latent heat flux (LE), respectively. The ratio of understory NEP (NEPU) to the ecosystem NEP (NEPE) and similarly calculated LEU/LEE during the daytime increased with vapor pressure deficit (VPD) at low VPD conditions (~ 2000 Pa) at half-hourly temporal scale. At high VPD conditions, however, NEPU/NEPE decreased with VPD, whereas LEU/LEE was maintained at the high level even at high VPD conditions. Despite large ranges of the estimates for the understory contributions, we conclude that the understory plays an important role in the carbon and energy balances of the black spruce ecosystem, and their contribution highly depends on the level of VPD.

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