TITLE: Toolik Snowfence Experiment: 1995-2001 Leaf Area 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: 1994 - 1998: OPP-9400083 -- ITEX / Comparative Responses of Moist and Dry Arctic Tundra to Altered Snow and Temperature Regimes 1999 - 2003: OPP-9907127 -- ITEX / Collaborative Research: Species Responses to Changes in Climate Across Arctic Gradients Using the North America ITEX Network (NATEX): Influences On Community and Ecosystem Processes 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 Leaf Area Index (LAI) data collected for the Toolik Snowfence Experiment from 1995 to 2001. 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: 19950713 to 20010728 Physical location of measurement: Toolik Field Station, Alaska USA (68.62710 N, 149.59322 W) DATA COLLECTION AND PROCESSING: Data were collected in 1995, 1998, 2000 and 2001 using a LAI-2000 Plant Canopy Analyzer (LI-COR Inc., Lincoln, Nebraska). LAI measurements were collected only at the moist tussock site because the plant canopy at the dry heath site is too low to accommodate the optical sensor. In all years, the 90 degree view cap was attached to the optical sensor. All measurements were consistently collected on cloudy, overcast days. To obtain LAI data, six measurements are taken per microsite (tussock or intertussock) at each plot. First, one reference measurement is taken above the canopy. Then, five measurements are taken below the canopy. This information is used to calculate summary LAI data. For a copy of the complete data set, including all 12 reference measurements at each plot, 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_LAI95-01.txt SUMMARY OF VARIABLES FOR 1995-2001 DATA 1. SITE: country/site/project 2. DATE/TIME_UTC: day/time of data collection, Coordinated Universal Time (YYYYMMDDHHmmss) 3. DATE/TIME_AK: day/time of data collection, Alaska Daylight Time (YYYYMMDDHHmmss) 4. LOCATION: moist site 5. ZONE: 0-6; east (E) or west (W) of the snowfence grid 6. PLOT: unique plot number, plots are 1 m2 7. MICROSITE: tussock (TUS) or intertussock (INT) 8. LAI: Leaf Area Index 9. SEL: standard error of LAI 10. DIFN: Diffuse Non-Interceptance, fraction of sky visible to the sensor 11. MTA: Mean Tilt angle (degrees) 12. SEM: standard error of MTA 13. SMP: number of pairs of above canopy and below canopy observations 14. NOTES 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. TREATMENT ITEX temperature manipulation. OTC: Open-topped chamber (warming), CTL: No chamber (control) PLOT LAI data is collected at the NDVI (Normalized Difference Vegetation Index) plots. NDVI plots are subjected to snow manipulation only. Temperature is not manipulated at any of the NDVI plots. LAI LAI (leaf area index) is a measure of the amount of foliage visible to the sensor. LAI is dimensionless but can be interpreted as 1/2 total green leaf area (one-sided area for broad leaves) in the plant canopy per unit ground area. This value can range from less than 0 (leaf area < ground area) to above 10 (leaf area > ground area). If leaf area is equal to ground area, then LAI is 1. DIFN DIFN (diffuse non-interceptance) is a measure of the fraction of sky that is not blocked by foliage. This value ranges from 0 (no sky visible to the sensor) to 1 (no foliage visible to the sensor). Because DIFN combines LAI and MTA into a single number, it is a single-value representation of canopy structure. MTA MTA (mean tilt angle) is a measure of foliage orientation. MTA ranges from 0 degrees (all foliage horizontal) to 90 degrees (all foliage vertical) with typical values ranging from 30's (predominantly horizontal leaves) to 60's (predominantly vertical leaves). CODES USED IN DATA SET In all years "-9999" indicates missing data. Questionable data is indicated by "****" in the NOTES column. DATA REMARKS: In 1995, LAI measures were not microsite specific and only 4 below canopy measures were taken. In 1998, LAI was measured at NDVI plots behind the snowfence only. FCT 16 (Bad Reading) was set to A(above canopy)/B(below canopy)=1 in all years except 2000. This mode is used when below canopy readings are likely to be made under little foliage. Without use of this setting, in our data set SMP varies from 1-5. LOCATION OF ORIGINAL DATA SHEETS: Boreal Ecology Cooperative Research Unit, University of Alaska, Fairbanks, Alaska, USA DOCUMENTATION AUTHOR: Original: Amy Breen Carroll, 7 January, 2002 Updated by: Amy Breen Carroll, 18 February, 2002 PRINCIPAL FIELD WORKERS: Andrew Borner PRINCIPAL POSTDOCS: Michael H. Jones Anna Arft PUBLICATIONS WHICH INCLUDE THESE DATA: None to date.