For the point frame (PF) and chamber flux (CH) measurements, GPS coordinates were measured with a handheld Garmin Etrex GPS unit while tracking at least five satellites.

Elevation for all sites was estimated from GoogleEarth; where position measurements were not recorded in the field, such as with the sites of dataloggers and monitoring sites, the position was also estimated from GoogleEarth maps.

Datalogger Sites - PAR and Relative Humidity
In order to monitor canopy conditions of the shrub species of interest--Betula nana and Salix pulchra--two CR1000 dataloggers (Campbell Scientific, 815 W. 1800, North Logan, UT, USA) were installed at the sites used for the ITEX shrub canopy studies at Toolik Field Station in Alaska the summer of 2012. The sites (see "Group" category) are labeled as "Upland" and "Outlet"--descriptions of the sample site in relation to Toolik Lake. The Upland site is colocated with Block 1 of the LTER shrub vegetation plots; the Outlet site is colocated with Block 2. The dataloggers were adjacent to, rather than within, LTER plots with the exception of B2BET which was located within the control (CT) plot of the LTER Shrub Block 2.

The following sensors were located at each datalogger site [B1BET, B1SALP, B2BET, B2SALP]:
PAR (LI-190SB Quantum Sensor):
(1) Mid-way within the canopy (approximately 40 cm above the soil)
(1) Below the canopy (approximately 10 cm above the soil)
Relative humidity (RH) and temperature sensors: HMP50/HMP60 Probe :
(1) Below the canopy (approximately 10 cm above the soil)

BF3 Data Logging
Whenever possible, the beam fraction sensor (BF3 sensor, manufactured by Delta-T Devices Ltd, Burwell Cambridge, UK) was programmed to log total and diffuse irradiance every five minutes on a CR800 datalogger (Campbell Scientific, 815 W. 1800, North Logan, UT, USA). The site initially chosen for this was behind a laboratory near Toolik Lake; this site was called "Lab2". While at least 10 meters from the nearest structure, it was thought that the proximity of the lab buildings might influence or even shade the BF3 sensor at low sun angles. Thus a second site was chosen--"Toolik Gate". This site is located at the entrance to the gravel pad of Toolik Field Station and had no nearby structures that could interfere with the BF3 readings.