Characterization of the carbon fluxes of a vegetated drained lake basin chronosequence on the Alaskan Arctic Coastal Plain

Abstract

Greenhouse gas fluxes from vegetated drained lake basins have been largely unstudied, although these land features constitute up to 47% of the land cover in the Arctic Coastal Plain in northern Alaska. To describe current and to better predict future sink/source activity of the Arctic tundra, it is important to assess these vegetated drained lake basins with respect to the patterns of and controls on gross primary production (GPP), net ecosystem exchange, and ecosystem respiration (ER). We measured CO 2 fluxes and key environmental variables during the 2007 growing season (June through August) in 12 vegetated drained lake basins representing three age classes (young, drained about 50 years ago; medium, drained between 50 and 300 years ago; and old, drained between 300 and 2000 years ago, as determined by Hinkel et al., 2003) in the Arctic Coastal Plain. Young vegetated drained lake basins had both the highest average GPP over the summer (11.4 gCO 2 m À2 day À1 ) and the highest average summer ER (7.3 gCO 2 m À2 day À1 ), while medium and old vegetated drained lake basins showed lower and similar GPP (7.9 and 7.2 gCO 2 m À2 day À1 , respectively), and ER (5.2 and 4 gCO 2 m À2 day À1 , respectively). Productivity decreases with age as nutrients are locked up in living plant material and dead organic matter. However, we showed that old vegetated drained lakes basins maintained relatively high productivity because of the increased development of ice-wedge polygons, the formation of ponds, and the re-establishment of very productive species. Comparison of the seasonal CO 2 fluxes and concomitant environmental factors over this chronosequence provides the basis for better understanding the patterns and controls on CO 2 flux across the coastal plain of the North Slope of Alaska and for more accurately estimating current and future contribution of the Arctic to the global carbon budget.

Mapping Arctic Tundra Vegetation Communities Using Field Spectroscopy and Multispectral Satellite Data in North Alaska, USA

“…The improved performance when including VIs in this study is especially useful in regards to monitoring plant productivity and ecosystem functioning. It has been shown previously [82,83] that NDVI can be linked heavily with net ecosystem exchange (NEE) [84,85] and CH 4 fluxes [25] for example. NDVI can be highly correlated with vegetation leaf area index (LAI), but also is invariant at higher LAI ranges and can be very sensitive to background variations in vegetation communities such as background soil and water [8].…”

Nonlinear controls on evapotranspiration in arctic coastal wetlands

“…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).…”

Characterizing Post-Drainage Succession in Thermokarst Lake Basins on the Seward Peninsula, Alaska with TerraSAR-X Backscatter and Landsat-based NDVI Data

“…Additionally, over time, basin productivity decreases as wet graminoid vegetation communities, including productive grass (Calamagrostis and Dupontia) and sedge fens (Carex aquatilis), are replaced by ericaceous bog and tussock-dominated ecosystems. Zona et al [32] have shown very high Gross Primary Productivity (GPP) for graminoid vegetation of younger DTLBs compared to the vegetation community of older DTLBs in Arctic ecosystems. This vegetative succession occurs as nutrients from the fresh lake sediments are consumed, permafrost aggradation causes limitations in rooting depth and liquid water availability, and ground ice formation and frost heave result in surface drying [10,32].…”

“…Zona et al [32] have shown very high Gross Primary Productivity (GPP) for graminoid vegetation of younger DTLBs compared to the vegetation community of older DTLBs in Arctic ecosystems. This vegetative succession occurs as nutrients from the fresh lake sediments are consumed, permafrost aggradation causes limitations in rooting depth and liquid water availability, and ground ice formation and frost heave result in surface drying [10,32]. Over time, low-centered ice wedge polygons start to develop in drained basins, indicating the accumulation of massive ground ice bodies [33], which eventually creates preconditions for new ponding and the beginning of a new thermokarst lake cycle [12].…”

“…We also utilized NDVI derived from Landsat-5 TM to aid in the interpretation of basin backscatter signal and the understanding of vegetation succession dynamics in DTLBs. NDVI is sensitive to plant biomass and can be useful to differentiate tundra vegetation type [42] in DTLBs at various stages [32,36]. This further helps to identify major biophysical parameters that are influencing basin backscatter.…”