Normalized difference vegetation index (NDVI) and Leaf area index (LAI) data from tussocks in the reciprocal transplant gardens at Toolik Lake, Coldfoot, and Sagwon in 2016.
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At the reciprocal transplant gardens (CF, TL, SG), single transplant tussock per plot repeatedly measured through the season. This was always the tussock closest to the boardwalk (normally tussock A). If tussock was too small, pick a different one. Every measurement tussock had all other species within the tussock removed (except moss). If other species grew over the tussock from outside these branches were also cut. The tussocks were maintain free of other species throughout the season to ensure NDVI of only the tussock was measured. Scans over every non-transpant (NT) tussock were also taken. These can be found in a line approximately 10-20 m from the transplant gardens, East of the gardens in Coldfoot and Toolik Lake and North of the garden at Sagwon.
A handheld Greenseeker (Trimble) was used to measure NDVI from the tussocks once per measurement day. This can be used in any light condition without a reference scan because it uses its own red light source. Two perpendicular measurements of the diameter of the tussock from a birds-eye view. Using a custom-made ruler which takes the measured diameter and multiplies it by 2.4 (which is the scaler for the field of view), the Greenseeker was held at the appropriate height with respect to the two diameters of the tussock and two scans directly above the tussock were taken. A mean NDVI was taken.
Using a relationship established with NDVI scans and destructive harvests :
(LAI = 11.898*NDVI3.3534 (R² = 0.8684))
LAI was calculated from the mean of the two NDVI scans
On some occastions measurements were not taken on some plots due to time constraints on the day or the tussock was being used for the demography study
Version 1: uploaded to data portal