TY - JOUR
T1 - Spatial and temporal variation in primary productivity (NDVI) of coastal Alaskan tundra
T2 - Decreased vegetation growth following earlier snowmelt
AU - Gamon, John A.
AU - Huemmrich, K. Fred
AU - Stone, Robert S.
AU - Tweedie, Craig E.
N1 - Funding Information:
We wish to thank Stan Houston, Erika Anderson, and Jean Van Dalen for assistance in field data collection. Dan Endres and other BRW staff provided helpful discussions and temperature data, David Longenecker and Ellsworth Dutton provided radiation data, Gina Sturm at the National Weather Service's Barrow office provided precipitation data, Cathy Seybold at the United States Department of Agriculture provided technical details of the soil moisture measurements, Suresh-Kumar Santhana-Vannan at ORNL DAAC provided advice on MODIS NDVI products, and the staff of the Barrow Arctic Science Consortium provided field logistical support. We are grateful to the Ukpeaġvik Iñupiat Corporation (UIC) for permitting access. Funding for the field component of this study was provided by IARC to J.A. Gamon and K.F. Huemmrich through the Desert Research Institute, Reno, Nevada. Additional support was provided by NASA and NSF , and final data analysis was supported by NSERC and iCORE/AITF grants to J.A. Gamon.
PY - 2013/2/5
Y1 - 2013/2/5
N2 - In 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.
AB - In 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.
KW - Arctic tundra productivity
KW - Drought
KW - Growing season length
KW - NDVI
KW - Remote sensing
KW - Snowmelt
KW - Spectral reflectance
KW - Temperature
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UR - http://www.scopus.com/inward/citedby.url?scp=84870210599&partnerID=8YFLogxK
U2 - 10.1016/j.rse.2012.10.030
DO - 10.1016/j.rse.2012.10.030
M3 - Article
AN - SCOPUS:84870210599
VL - 129
SP - 144
EP - 153
JO - Remote Sensing of Environment
JF - Remote Sensing of Environment
SN - 0034-4257
ER -