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Spatial and Temporal Variation in Primary Productivity (NDVI) of Coastal Alaskan Tundra: Decreased Vegetation Growth Following Earlier SnowmeltIn the Arctic, earlier snowmelt and longer growing seasons due to warming have been hypothesized to increase vegetation productivity. Using the Normalized Difference Vegetation Index (NDVI) from both field and satellite measurements as an indicator of vegetation phenology and productivity, we monitored spatial and temporal patterns of vegetation growth for a coastal wet sedge tundra site near Barrow, Alaska over three growing seasons (2000-2002). Contrary to expectation, earlier snowmelt did not lead to increased productivity. Instead, productivity was associated primarily with precipitation and soil moisture, and secondarily with growing degree days, which, during this period, led to reduced growth in years with earlier snowmelt. Additional moisture effects on productivity and species distribution, operating over a longer time scale, were evident in spatial NDVI patterns associated with microtopography. Lower, wetter regions dominated by graminoids were more productive than higher, drier locations having a higher percentage of lichens and mosses, despite the earlier snowmelt at the more elevated sites. These results call into question the oft-stated hypothesis that earlier arctic growing seasons will lead to greater vegetation productivity. Rather, they agree with an emerging body of evidence from recent field studies indicating that early-season, local environmental conditions, notably moisture and temperature, are primary factors determining arctic vegetation productivity. For this coastal arctic site, early growing season conditions are strongly influenced by microtopography, hydrology, and regional sea ice dynamics, and may not be easily predicted from snowmelt date or seasonal average air temperatures alone. Our comparison of field to satellite NDVI also highlights the value of in-situ monitoring of actual vegetation responses using field optical sampling to obtain detailed information on surface conditions not possible from satellite observations alone.
Document ID
20140017189
Acquisition Source
Goddard Space Flight Center
Document Type
Reprint (Version printed in journal)
Authors
Gamon, John A.
(California State Univ. Los Angeles, CA, United States)
Huemmrich, K. Fred
(Maryland Univ. Baltimore County Baltimore, MD, United States)
Stone, Robert S.
(National Oceanic and Atmospheric Administration Boulder, CO, United States)
Tweedie, Craig E.
(Texas Univ. El Paso, TX, United States)
Date Acquired
December 9, 2014
Publication Date
January 1, 2015
Publication Information
Publication: Remote Sensing of Environment
Publisher: Elsevier
Volume: 129
Subject Category
Meteorology And Climatology
Report/Patent Number
GSFC-E-DAA-TN14745
Funding Number(s)
CONTRACT_GRANT: NNX10AT36A
Distribution Limits
Public
Copyright
Public Use Permitted.
Keywords
Growing
Arctic tundra
productivity
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