TITLE: 1999 Ivotuk Biomass, NDVI, LAI Data AUTHORS Howard E. Epstein Department of Environmental Sciences University of Virginia Charlottesville, VA 22904-4123 (434) 924-4308 (phone) (434) 982-2137 (Fax) hee2b@virginia.edu Sebastian M. Riedel, University of Virginia Donald A. (Skip) Walker, University of Alaska Fairbanks FUNDING SOURCE – NSF OPP-9908829 DATA SET OVERVIEW During the 1999 growing season at Ivotuk, AK, we measured normalized difference vegetation index (NDVI), leaf area index (LAI) and the aboveground biomass of a variety of plant types/parts biweekly for four tundra vegetation types: moist acidic tundra (MAT), mossy tussock tundra (MT), moist non-acidic tundra (MNT) and shrubby tundra (ST). Data were collected 6-7 times between June and August. Ivotuk, AK is located at 68.49 °N and 155.74 °W; elevation ranges from approximately 500-600m. INSTRUMENTS NDVI We used an Analytical Spectral Devices (Boulder, CO) FieldSpec spectroradiometer to measure the reflectance of visible and near infrared wavelengths from the land surface. The instrument measures radiance in 1.4 nm intervals from 350-1050 nm (512 channels). LAI We used a LI-COR LAI-2000 to estimate leaf area index. This instrument is used to measure solar irradiance both above (or outside) and below vegetation canopies, and calculates LAI using a radiative transfer model. Biomass Biomass values were calculated by harvesting, sorting, drying and weighing vegetation components. DATA COLLECTION We measured normalized difference vegetation index (NDVI), leaf area index (LAI) and the aboveground biomass of a variety of plant types/parts biweekly at Ivotuk, AK for four tundra vegetation types: moist acidic tundra (MAT), mossy tussock tundra (MT), moist non-acidic tundra (MNT) and shrubby tundra (ST). Data were collected 6-7 times between June and August of 1999; the actual dates vary depending on the measurement and the grid being sampled (i.e. it was impossible to collect all of the data, even for a single grid on the same day). Each of the four grids is 100m X 100m with grid points spaced every 10m; there are therefore 121 grid points in each grid. NDVI NDVI data were measured biweekly for each grid (vegetation type) at 20 randomly selected grid points. The same grid points were sampled during each biweekly time period. Four replicate measurements were taken at each grid point, one meter from the point in each of the four cardinal directions, and averaged to yield a mean value. The fiber optic sensor of the radiometer was held approximately 1.5 m above the ground surface pointing downward, yielding a footprint of approximately 0.35 m². NDVI was calculated as (NIR-RED)/(NIR+RED), where NIR is the near infrared reflectance (725-1000nm) and RED is the red reflectance (580-680nm). LAI LAI data were estimated biweekly for each grid at 20 randomly selected grid points (the same points at which the NDVI data were taken). At each grid point, one above canopy measurement was taken, and four below canopy measurements were taken (one meter from the grid point in each of the cardinal directions), and the instrument calculated a single LAI value for each grid point. Aboveground Biomass Aboveground phytomass was collected biweekly from 10 randomly selected 20 X 50 cm plots within each grid. Phytomass sampling occurred near, but not within, the footprints of the NDVI and LAI measurements. On the 4th sampling period (July 15-26), twenty plots (instead of 10) were harvested for MAT and MT, and on the 5th sampling period (July 27 – Aug. 7), twenty plots were harvested for MNT and ST. Vascular plants were clipped at the top of the moss layer, and mosses were clipped at the base of the green layer. Phytomass samples were sorted into six categories: bryophytes, lichens, horsetails, other forbs, graminoids and shrubs. Graminoids were further divided into live and dead. Shrubs were divided into deciduous and evergreen, which were further separated into woody, foliar live and foliar dead components. DATA FORMAT Data are column delimited in either ASCII or Excel. The following are descriptions of each of 12 data sheets found either in the Excel spreadsheet or separately as ASCII files. Mean NDVI and LAI Columns are DATE of LAI sample, MEAN LAI, STANDARD ERROR OF LAI, and DATE of NDVI sample, MEAN NDVI, STANDARD ERROR OF NDVI. Means and standard errors are across 20 samples for each data. Data are separated by the four tundra vegetation types. NDVI Raw Data Columns are VEGETATION TYPE, GRID POINT and NDVI by DATE. VEGETATION TYPES are moist acidic tundra (MAT), moist nonacidic tundra (MNT), mossy tussock tundra (MT) and shrub tundra (ST). Twenty grid points were sampled per vegetation type per date. NDVI values are means of four measurement, each one meter from the grid point. LAI Raw Data Columns are VEGETATION TYPE, GRID POINT and LAII by DATE. VEGETATION TYPES are moist acidic tundra (MAT), moist nonacidic tundra (MNT), mossy tussock tundra (MT) and shrub tundra (ST). Twenty grid points were sampled per vegetation type per date. LAI values are calculated from one above canopy measurement and four below canopy measurements at each grid point. Seasonal Mean Phytomass Columns are PLANT TISSUE TYPE by VEGETATION TYPE and PHYTOMASS by DATE. Plant tissue types are: Forbs (excluding horsetail), Graminoids, Horsetail, Lichen, Moss, Deciduous Shrub Woody, Deciduous Shrub Foliar, Evergreen Shrub Woody, Evergreen Shrub Foliar, Total Shrub, Total Aboveground Live Phytomass, Total Standing Dead. All tissue types (except Total Standing Dead) are aboveground live only. Phytomass by Date is recorded in g/m² ? one standard error. Peak Phytomass Data Columns are PLANT TYPE and PHYTOMASS BY VEGETATION TYPE. Plant types are Graminoid, Moss, Lichen, Horsetail, Forb, and Shrub. Phytomass values are g/m² by vegetation type. Total phytomass and one standard error are calculated for each vegetation type. The date of peak aboveground live biomass is also provided. Phytomass Periods 1-7 Columns are DATE, VEGETATION TYPE, PLOT (Grid Point), and PHYTOMASS BY PLANT TISSUE TYPE. Phytomass values are in grams per 0.1 m², because the area of harvest was 20 X 50 cm (0.1. m²). Standard Deviation, Standard Error and Coefficient of Variation are also calculate by DATE and VEGETATION TYPE. There is a separate Excel Worksheet or ASCII file for each of seven sampling periods.