Needle-Level Chlorophyll Fluorescence Measurements from Alaska and Idaho Forests

Two evergreen needleleaf forest sites in Alaska and Idaho, USA, provide in situ measurements of needle-level chlorophyll fluorescence (ChlF) and modeled irradiance. The dataset contains observations from 36 white spruce trees sampled in Alaska in July 2017 and 10 grand fir trees sampled in Idaho in July 2019. It was produced by the National Aeronautics and Space Administration (NASA) for the ABoVE campaign to study photosynthetic activity.

Use Cases

• Calibrating or validating remote sensing models of chlorophyll fluorescence using ground-truth measurements of quantum yield (Ft, Fv/Fm).
• Studying diurnal patterns of photosynthetic efficiency under variable light conditions using time-series irradiance data (top-of-canopy and needle-level).
• Analyzing species-specific (Picea glauca, Abies grandis) or site-specific (forest-tundra ecotone vs. montane forest) differences in light-adapted fluorescence.
• Investigating the relationship between modeled irradiance products and directly measured needle-level irradiance (Idaho site only).

Strengths

• Provides contemporaneous, ground-based chlorophyll fluorescence and irradiance data for validating satellite products.
• Includes direct in situ irradiance measurements at the Idaho site for model verification.
• Covers two distinct forest ecosystems (Alaskan forest-tundra ecotone and Idaho montane forest) and two tree species.
• Measurements were taken during clear-sky, near-solstice periods to capture a broad range of sunlit-shading patterns.

Limitations

• Key metadata such as row count, file size, and specific column names are unavailable across all platforms.
• Conflicting last updated dates exist between sources (2019-07-06 on NASA Earthdata and 2026-03-13 on Data.gov).
• Temporal coverage is limited to two specific days in 2017 and 2019, restricting analysis of seasonal trends.

Provenance

Source

National Aeronautics and Space Administration

Collection Method

In situ measurements from a pulse amplitude modulated (PAM) fluorometer and a handheld pyranometer, combined with modeled irradiance products.

Time Range

2017-07-07 to 2019-07-06

Freshness

2026-03-13 20:13:38.773967

Geography

Northern Alaska (forest-tundra ecotone near Dalton Highway) and McCall, Idaho (montane forest), USA.