Explanation to data of "Root heterogeneity along an arctic elevational gradient: the importance of resolution",
by Sabrina Träger & Scott D. Wilson, Functional Ecology.

Presented are data of root length (in mm) for each single root ("root_ID") per minirhizotron image ("window")
within a specific minirhizotron tube ("tube"), on a specific sampling date (June, August, September).
Roots first appearance during sampling (June, August, or September) is noted in "appeared_date".
Roots disappearance during sampling is noted in "death_date". If nothing is mentioned, roots
did not disappear ("-").

Four elevations were sampled, each having 10 tubes (except 500 m, where one tube was missing).
In each tube, 30 contiguous images ("windows") were sampled.

Tubes 1-10 are at 500 m a.s.l. (Tube 5 missing)
Tubes 11-20 are at 600 m a.s.l.
Tubes 21-30 are at 750 m a.s.l.
Tubes 31-40 are at 1100 m a.s.l.