ABoVE: Needle-Level Chlorophyll Fluorescence, Alaska and Idaho, USA, 2017 and 2019

This dataset provides the results of in situ measurements of needle-level chlorophyll fluorescence (ChlF) obtained from a pulse amplitude modulated (PAM) fluorometer from evergreen needleleaf forested sites one in Alaska and one in Idaho. Measured light-adapted minimal fluorescence (Ft) is reported as the quantum yield of fluorescence and light-adapted variable fluorescence over maximal fluorescence (Fv/Fm) and is reported as the quantum yield of photosystem II. Also reported for both sites are two modeled irradiance products: (1) the top-of-canopy instantaneous irradiance (W/m2) and (2) needle-level irradiance (W/m2) that was modeled to account for shadow casting and canopy orientation in modulating direct radiation. Both products were modeled to be contemporaneous with ChlF observations. At the Idaho site only, needle-level irradiance (W/m2) was measured in situ with a handheld pyranometer. The Alaska field site is located in the northern latitudinal forest-tundra ecotone (FTE) near the Dalton Highway in Northern Alaska. Thirty-six Picea glauca (white spruce) trees were sampled on 2017-07-07 to 2017-07-08. The Idaho field site is located in a montane forest near McCall, Idaho. Ten selected Abies grandis (grand fir) trees were sampled on 2019-07-05 to 2019-07-06. Measurement of needle-level ChlF occurred during clear-sky conditions such that the canopies experienced a broad range of variability in sunlit-shading patterns across the day during these near-solstice periods.

Data and Resources

Additional Info

Field Value
Maintainer Earthdata Forum
Last Updated June 2, 2026, 15:52 (UTC)
Created April 1, 2025, 14:07 (UTC)
accessLevel public
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harvest_source_id b99e41c6-fe79-4c19-bbc3-9b6c8111bfac
harvest_source_title Science Discovery Engine
identifier 10.3334/ORNLDAAC/1785
license https://www.usa.gov/government-works
modified 2026-06-01T22:15:58Z
programCode {026:000}
publisher ORNL_DAAC
resource-type Dataset
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source_hash b83485991bb4df3a40ac99f539b6b2674a3ff6473776c7d64c2ea8341bca242b
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spatial ["CARTESIAN", [{"WestBoundingCoordinate": -149.754, "NorthBoundingCoordinate": 67.9947, "EastBoundingCoordinate": -116.067, "SouthBoundingCoordinate": 44.9061}]]
temporal 2017-07-07/2019-07-06
theme {"Earth Science"}