At the experimental burn plots at Toolik Lake, ion exchange membranes were used to measure nutrient availability over two time periods: Early season (June) and mid season (July). Membranes were deployed in the field for either 21 or 20 days, depending on logistical constraints. The experiment is arranged in 10 paired plots of burnt and non-burnt plots (burn control), numbered from 1 to 10 from the access road towards the Brooks range.

Membranes were charged prior to placement in the field according to Weintraub Lab protocol:

'Anion and cation exchange resin membranes (GE Power and Water, via Maltz sales: anion model #3009749; cation model #3009753; Qian and Schoenau 2005), cut into 2x6 cm strips, will be inserted into the soil using a putty knife as a pilot, marked with an attached piece of string, and left in the soil for 20 days. The resin membranes will then be collected and immediately placed into 50 ml centrifuge tubes with 35 ml of 2M KCl. The tubes will be gently shaken horizontally on a shaker table for 1 hour at which point the extractant will be frozen in microcentrifuge tubes for later analysis. For each set of field resins, 3 anion and 3 cation resins will be kept refrigerated in Ziploc bags and analyzed as blanks, processed in exactly the same way except for field deployment. Between uses, resin membrane strips can be recharged by shaking in five sequential 1 hr 0.5 M HCl rinses, followed by shaking in a 1 hr 0.5 M NaHCO3 rinse.'

Some notes on inserting the membranes:

Using a created knife, cut two  slits into the soil 4 cm wide , 10 cm deep at 45 degrees to the ground, 3 cm apart from each other. Carefully slide the membranes (one cation, one anion) into the slits so that the top is 2 cm from the bottom on the moss layer (firmly in the organic horizon). Press the soil back together so that there is complete contact between membrane and soil.

Pairs of membranes were inserted in tussocks and in intertussock pairs, in the center of each plot  approximately 20- 40 cm apart. Care was taken to not touch membranes with bare skin as they were extracted, they were rinsed in the field with deionized  water then fully rinsed prior to extraction in the lab.