TITLE: Toolik Snowfence Experiment: 2002 Normalized Difference Vegetation Index PRINCIPAL INVESTIGATOR: Dr. Marilyn Walker Leader, Boreal Ecology Cooperative Research Unit USFS PNW Research Station and University of Alaska Fairbanks Boreal Ecology Cooperative Research Unit School of Agriculture and Land Resources Management P.O. Box 756780 University of Alaska Fairbanks Fairbanks, AK 99775-6780 Phone: 907-474-2424 Fax: 907-474-6251 E-mail: ffmdw@uaf.edu FUNDING SOURCE: National Science Foundation ARCTIC SYSTEM SCIENCE PROGRAM: Land-Atmosphere-Ice Interactions (LAII) and The International Tundra Experiment (ITEX) GRANT TITLES AND GRANT NUMBERS: 1999 - 2003: OPP-9996383 -- ITEX / Comparative Responses of Moist and Dry Arctic Tundra to Altered Snow and Temperature Regimes CONDITIONS FOR USE AND CITATION: For permission to use these data, contact the Principal Investigator. Grant numbers must be cited in any manuscripts resulting from these data. In addition, a copy of the manuscript must be sent to the PI. DATA SET OVERVIEW: This file contains Normalized Difference Vegetation Index (NDVI) data collected for the Toolik Snowfence Experiment in 2002. The Toolik Snowfence Experiment (part of the International Tundra Experiment network) examines the short- and long-term effects of increased snow depth (shortened growing season) and increased summer temperature on arctic tundra vegetation. The goal of this project is to assess potential changes in tundra plant communities in response to global climate change. Time period covered by data: 20020530 to 20020607 Physical location of measurement: Toolik Field Station, Alaska USA (68.62710 N, 149.59322 W) DATA COLLECTION AND PROCESSING: Data were collected using a PS-II Spectral Analyzer (Analytical Spectral Devices Inc., Boulder, Colorado) exclusively at the NDVI plots established at the moist tussock and dry tundra sites. NDVI plots are subjected to snow manipulation only. Temperature is not manipulated at any of the NDVI plots. All measurements were consistently collected on cloudless days when the sun is at its highest point (from 1000 to 1400 Alaska Daylight Time). NDVI values are the mean of 5 readings, one/second, measured from circular sweeps of each plot with the sensor positioned approximately 0.5 m from the ground surface. For a copy of the complete spectral data set, contact the principal investigator. The Toolik Snowfence Experiment's design and manipulation are described further in: Walker, M. D., D. A. Walker, J. M. Welker, A. M. Arft, T. Bardsley, P. D. Brooks, J. T. Fahnestock, M. H. Jones, M. Losleben, A. N. Parsons, T. R. Seastedt and P. L. Turner. 1999. Long-term experimental manipulation of winter snow regime and summer temperature in arctic and alpine tundra. Hydrological Processes 13: 2315-2330. DATA FORMAT: File name: USTOOLIK_NDVI02.txt SUMMARY OF VARIABLES FOR 2002 DATA 1. SITE: country/site/project 2. DATE: date of data collection (YYYYMMDD) 3. LOCATION: site; moist or dry 4. ZONE: 0-6; E (east) or W (west) of the grid 5. PLOT: unique plot number, plots are 1 m2 6. NDVI: Normalized Difference Vegetation Index 7. RED_BAND: visible spectral measurement (um) 8. NIR_BAND: near infrared spectral measurement (um) DESCRIPTION OF SELECT VARIABLES: SITE USTOOLIK: Toolik Field Station, Alaska, USA; Comparative responses of moist and dry arctic tundra to altered snow and temperature regimes LOCATION Research site: Snowfences are erected and grids established at both a moist tussock site (68.62032 N, 149.59931) and a dry heath site (68.62261 N, 149.59589 W). In addition, monitored plots are established where a natural snowdrift occurs. This site is referred to as the snowfield. ZONE Snow manipulation: A 60 m snowfence is aligned on an east-west axis at both the moist and dry sites. Both snowfences are perpendicular to the predominant winter winds from the Brooks Range to the south, effectively creating a leeward drift 50-60 m long on the north side of the fence. An established grid on the north side of the fence divides the drift into 6 parallel zones (60 m x 10 m). Zone number increases from 1 to 6, as distance from the snowfence increases. Zones 1, 2 and 3 accumulate the most snow (2-3 m), while zones 4, 5 and 6 accumulate the least snow (0.5-2 m). Zone 0 (the control) is located adjacent to the snowfence grid and does not receive supplemental snow. NDVI NDVI is calculated from the visible and near-infrared light reflected by vegetation [(NIR - RED) / (NIR + RED)]. NDVI ranges from -1 to +1. Positive values correspond to vegetated surfaces and negative values generally correspond to non-vegetated surfaces (eg. rock, water, soil). Healthy vegetation absorbs most of the visible light that hits it and reflects a large portion of the near- infrared light. Unhealthy or sparse vegetation reflects more visible light and less near-infrared light. CODES USED IN DATA SET In all years "-9999" indicates missing data. DATA REMARKS: Our access to the PS-II was limited to early season in 2002. NDVI data collected at plots 46-60 at the moist site on 7 June, 2002 are missing. LOCATION OF ORIGINAL DATA SHEETS: Boreal Ecology Cooperative Research Unit, University of Alaska, Fairbanks, Alaska, USA DOCUMENTATION AUTHOR: Original: Amy Breen Carroll, 17 January, 2003 PRINCIPAL FIELD WORKERS: Amy Breen Carroll Miyuki Tachibana PRINCIPAL POSTDOCS: Henrik Wahren PUBLICATIONS WHICH INCLUDE THESE DATA: None to date.