Light-stress avoidance mechanisms in a<i>Sphagnum</i>-dominated wet coastal Arctic tundra ecosystem in Alaska

Zona, Donatella; Oechel, W. C.; Richards, James H.; Hastings, Steven J.; Kopetz, Irene; Ikawa, Hiroki; Oberbauer, Steven F.

doi:10.1890/10-0822.1

Cited by 36 publications

(41 citation statements)

References 51 publications

(73 reference statements)

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“…This is because the soil water potential to initiate stomata closure was never reached. In addition, as mosses represent the majority of the live biomass (Zona et al, 2011), one could argue that they represent a key hydrologic pathway between land and atmospheric systems. And, in fact, boreal mosses are known to act as a heat and moisture "rectifier", allowing heat and moisture fluxes to proceed when they are moist, and reducing heat and moisture fluxes under hot and dry conditions when the uppermost moss surfaces are dry (Oechel and Van Cleve, 1986).…”

Section: Discussionmentioning

confidence: 99%

“…LAI at the CM site reached 1.4 in mid-August of 2001 (Mano, 2003). Mid-August LAI reached 0.58 in 2006 at the BE vegetated, drained lake, where the vascular plant coverage is dominated by Carex aquatilis (Zona et al, 2011). Sedges at the BE site did not experience water stress in midJuly of 2008 (P. Olivas, unpublished data).…”

Section: Site Descriptionmentioning

confidence: 99%

“…Bryophytes represent between 60 and 95 % of the overall live biomass in similar wet meadow communities , with much of the variation due to small-scale heterogeneity associated with micro-topography Hollister and Flaherty, 2010). Across the BE drained lake bed, mosses represent most of the live above-ground biomass (Zona et al, 2009(Zona et al, , 2010(Zona et al, , 2011. Up to 60 % of the ecosystem's net daytime CO 2 uptake at the end of the growing season at BE is represented by Sphagnum (Zona et al, 2011).…”

Section: Site Descriptionmentioning

confidence: 99%

“…Across the BE drained lake bed, mosses represent most of the live above-ground biomass (Zona et al, 2009(Zona et al, , 2010(Zona et al, , 2011. Up to 60 % of the ecosystem's net daytime CO 2 uptake at the end of the growing season at BE is represented by Sphagnum (Zona et al, 2011). Accordingly, controls on evapotranspiration rates from this landscape are likely dominated by moss evaporation processes.…”

Section: Site Descriptionmentioning

confidence: 99%

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Nonlinear controls on evapotranspiration in arctic coastal wetlands

et al. 2011

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Abstract. Projected increases in air temperature and precipitation due to climate change in Arctic wetlands could dramatically affect ecosystem function. As a consequence, it is important to define controls on evapotranspiration, the major pathway of water loss from these systems. We quantified the multi-year controls on midday Arctic coastal wetland evapotranspiration, measured with the eddy covariance method at two vegetated, drained thaw lake basins near Barrow, Alaska. Variations in near-surface soil moisture and atmospheric vapor pressure deficits were found to have nonlinear effects on midday evapotranspiration rates. Vapor pressure deficits (VPD) near 0.3 kPa appeared to be an important hydrological threshold, allowing latent heat flux to persistently exceed sensible heat flux. Dry (compared to wet) soils increased bulk surface resistance (water-limited). Wet soils favored ground heat flux and therefore limited the energy available to sensible and latent heat flux (energy-limited). Thus, midday evapotranspiration was suppressed from both dry and wet soils but through different mechanisms. We also found that wet soils (ponding excluded) combined with large VPD, resulted in an increased bulk surface resistance and therefore suppressing evapotranspiration below its potential rate (Priestley-Taylor α < 1.26). This was likely caused by the limited ability of mosses to transfer moisture during large atmospheric demands. Ultimately, in addition to net radiation, the various controlling factors on midday evapotranspiration (i.e., near-surface soil moisture, atmospheric vapor pressure, Correspondence to: A. K. Liljedahl (akliljedahl@alaska.edu) and the limited ability of saturated mosses to transfer water during high VPD) resulted in an average evapotranspiration rate of up to 75 % of the potential evapotranspiration rate. These multiple limitations on midday evapotranspiration rates have the potential to moderate interannual variation of total evapotranspiration and reduce excessive water loss in a warmer climate. Combined with the prevailing maritime winds and projected increases in precipitation, these curbing mechanisms will likely prevent extensive future soil drying and hence maintain the presence of coastal wetlands.

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Section: Discussionmentioning

confidence: 99%

Section: Site Descriptionmentioning

confidence: 99%

Section: Site Descriptionmentioning

confidence: 99%

Section: Site Descriptionmentioning

confidence: 99%

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Nonlinear controls on evapotranspiration in arctic coastal wetlands

et al. 2011

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“…Moss cover usually dominates the surface in high latitudes, and has been shown to play a key role in modifying temperature and moisture conditions in Arctic soils (Beringer et al, 2001;Zona et al, 2011b;Kim et al, 2014). Evaporation from mosses comprises a significant portion of the latent heat flux in Arctic ecosystems (McFadden et al, 2003;.…”

Section: Vegetation Impactmentioning

confidence: 99%

Shifted energy fluxes, increased Bowen ratios, and reduced thaw depths linked with drainage-induced changes in permafrost ecosystem structure

et al. 2017

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Abstract. Hydrologic conditions are a key factor in Arctic ecosystems, with strong influences on ecosystem structure and related effects on biogeophysical and biogeochemical processes. With systematic changes in water availability expected for large parts of the northern high-latitude region in the coming centuries, knowledge on shifts in ecosystem functionality triggered by altered water levels is crucial for reducing uncertainties in climate change predictions. Here, we present findings from paired ecosystem observations in northeast Siberia comprising a drained and a control site. At the drainage site, the water table has been artificially lowered by up to 30 cm in summer for more than a decade. This sustained primary disturbance in hydrologic conditions has triggered a suite of secondary shifts in ecosystem properties, including vegetation community structure, snow cover dynamics, and radiation budget, all of which influence the net effects of drainage. Reduced thermal conductivity in dry organic soils was identified as the dominating drainage effect on energy budget and soil thermal regime. Through this effect, reduced heat transfer into deeper soil layers leads to shallower thaw depths, initially leading to a stabilization of organic permafrost soils, while the long-term effects on permafrost temperature trends still need to be assessed. At the same time, more energy is transferred back into the atmosphere as sensible heat in the drained area, which may trigger a warming of the lower atmospheric surface layer.

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Tundra water budget and implications of precipitation underestimation

Liljedahl

Hinzman

Kane

et al. 2017

Water Resources Research

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Difficulties in obtaining accurate precipitation measurements have limited meaningful hydrologic assessment for over a century due to performance challenges of conventional snowfall and rainfall gauges in windy environments. Here, we compare snowfall observations and bias adjusted snowfall to end‐of‐winter snow accumulation measurements on the ground for 16 years (1999–2014) and assess the implication of precipitation underestimation on the water balance for a low‐gradient tundra wetland near Utqiagvik (formerly Barrow), Alaska (2007–2009). In agreement with other studies, and not accounting for sublimation, conventional snowfall gauges captured 23–56% of end‐of‐winter snow accumulation. Once snowfall and rainfall are bias adjusted, long‐term annual precipitation estimates more than double (from 123 to 274 mm), highlighting the risk of studies using conventional or unadjusted precipitation that dramatically under‐represent water balance components. Applying conventional precipitation information to the water balance analysis produced consistent storage deficits (79 to 152 mm) that were all larger than the largest actual deficit (75 mm), which was observed in the unusually low rainfall summer of 2007. Year‐to‐year variability in adjusted rainfall (±33 mm) was larger than evapotranspiration (±13 mm). Measured interannual variability in partitioning of snow into runoff (29% in 2008 to 68% in 2009) in years with similar end‐of‐winter snow accumulation (180 and 164 mm, respectively) highlights the importance of the previous summer's rainfall (25 and 60 mm, respectively) on spring runoff production. Incorrect representation of precipitation can therefore have major implications for Arctic water budget descriptions that in turn can alter estimates of carbon and energy fluxes.

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Light-stress avoidance mechanisms in aSphagnum-dominated wet coastal Arctic tundra ecosystem in Alaska

Cited by 36 publications

References 51 publications

Nonlinear controls on evapotranspiration in arctic coastal wetlands

Nonlinear controls on evapotranspiration in arctic coastal wetlands

Shifted energy fluxes, increased Bowen ratios, and reduced thaw depths linked with drainage-induced changes in permafrost ecosystem structure

Tundra water budget and implications of precipitation underestimation

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