Phytomass, LAI, and NDVI in northern Alaska: Relationships to summer warmth, soil pH, plant functional types, and extrapolation to the circumpolar Arctic

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Read Full Article (file size: 757353 bytes) Cited by JOURNAL OF GEOPHYSICAL RESEARCH, VOL. 108, NO. D2, 8169, doi:10.1029/2001JD000986, 2003 Phytomass, LAI, and NDVI in northern Alaska: Relationships to summer warmth, soil pH, plant functional types, and extrapolation to the circumpolar Arctic D. A. Walker Institute of Arctic Biology, University of Alaska Fairbanks, Fairbanks, Alaska, USA H. E. Epstein Department of Environmental Sciences, University of Virginia, Charlottesville, Virginia, USA G. J. Jia Department of Environmental Sciences, University of Virginia, Charlottesville, Virginia, USA A. Balser Institute of Arctic Biology, University of Alaska Fairbanks, Fairbanks, Alaska, USA C. Copass Institute of Arctic Biology, University of Alaska Fairbanks, Fairbanks, Alaska, USA E. J. Edwards Institute of Arctic Biology, University of Alaska Fairbanks, Fairbanks, Alaska, USA W. A. Gould International Institute of Tropical Forestry, USDA Forest Service, San Juan, Puerto Rico J. Hollingsworth Institute of Arctic Biology, University of Alaska Fairbanks, Fairbanks, Alaska, USA J. Knudson Institute of Arctic Biology, University of Alaska Fairbanks, Fairbanks, Alaska, USA H. A. Maier Institute of Arctic Biology, University of Alaska Fairbanks, Fairbanks, Alaska, USA A. Moody Institute of Arctic Biology, University of Alaska Fairbanks, Fairbanks, Alaska, USA M. K. Raynolds Institute of Arctic Biology, University of Alaska Fairbanks, Fairbanks, Alaska, USA Abstract We examined the effects of summer warmth on leaf area index (LAI), total aboveground phytomass (TAP), and normalized difference vegetation index (NDVI) across the Arctic bioclimate zone in Alaska and extrapolated our results to the circumpolar Arctic. Phytomass, LAI, and within homogeneous areas of vegetation on acidic and nonacidic soils were regressed against the total summer warmth index (SWI) at 12 climate stations in northern Alaska (SWI = sum of mean monthly temperatures greater than 0°C). SWI varies from 9°C at Barrow to 37°C at Happy Valley. A 5°C increase in the SWI is correlated with about a 120 g m⁻² increase in the aboveground phytomass for zonal vegetation on acidic sites and about 60 g m⁻² on nonacidic sites. Shrubs account for most of the increase on acidic substrates, whereas mosses account for most of the increase on nonacidic soils. LAI is positively correlated with SWI on acidic sites but not on nonacidic sites. The NDVI is positively correlated with SWI on both acidic and nonacidic soils, but the NDVI on nonacidic parent material is consistently lower than the NDVI on acidic substrates. Extrapolation to the whole Arctic using a five-subzone zonation approach to stratify the circumpolar NDVI and phytomass data showed that 60% of the aboveground phytomass is concentrated in the low-shrub tundra (subzone 5), whereas the high Arctic (subzones 1–3) has only 9% of the total. Estimated phytomass densities in subzones 1–5 are 47, 256, 102, 454, and 791 g m⁻², respectively. Climate warming will likely result in increased phytomass, LAI, and NDVI on zonal sites. These changes will be most noticeable in acidic areas with abundant shrub phytomass. Published 31 January 2003. Index Terms: 0315 Atmospheric Composition and Structure: Biosphere/atmosphere interactions; 1640 Global Change: Remote sensing; 9315 Information Related to Geographic Region: Arctic region. Read Full Article (file size: 757353 bytes) Cited by Citation: Walker, D. A., et al. (2003), Phytomass, LAI, and NDVI in northern Alaska: Relationships to summer warmth, soil pH, plant functional types, and extrapolation to the circumpolar Arctic, J. Geophys. Res., 108(D2), 8169, doi:10.1029/2001JD000986. Copyright 2003 by the American Geophysical Union.

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