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Functional type contribution to the carbon balance of arctic vegetation at Barrow, AK .
Houston, Stan*,1,2, Gamon, John1,2, Huemmrich, K.2,3, Anderson, Erika2,4, 1 California State University at Los Angeles, Los angeles, CA2 Desert Research Institute, Reno, NV3 University of Maryland, NASA GSFC, Washington, DC4 Kalamazoo College, Kalamazoo, MI
ABSTRACT- The objective of this study was to use remote sensing and gas exchange techniques to assess the photosynthetic physiology of primary cover types and evaluate their contribution to ecosystem flux of arctic tundra. The vegetation at Barrow can be broken down into three fundamentally distinct types (vascular plants, mosses, and lichens) that differ optically and physiologically. The three cover types exhibited contrasting reflectance spectra when sampled at a small scale (~15 cm patches) using a portable spectrometer. Of the three groups, lichen spectra were the most distinct, largely due to their pigment composition, which contrasted strongly from that of the vascular plants and mosses. Vascular plants showed a strong seasonality in NDVI (Normalized Difference Vegetation Index, a measure of canopy greenness derived from reflectance), while mosses and lichens did not. Vascular plants showed a strong correlation between NDVI and independent measures of photosynthetic activity (gas exchange and chlorophyll fluorescence), indicating that NDVI is linked to the photosynthetic performance of vascular plants in this ecosystem. Ecosystem flux was modeled based on the seasonal course of optical properties and photosynthetic rate for the three functional types, showing that a change in species composition will have an effect on the local carbon balance. These results also demonstrate that remote sensing can detect changes in species composition and carbon balance for this tundra ecosystem.
KEY WORDS: reflectance, ndvi, carbon, flux