Establish ant enclosures
Install 36 ant enclosures in the montane meadow during summer 2010. Each enclosure was 5 m in diameter and encircled a central F. obscuripes nest. Male fern rhizomes along landscape edges (15 cm tall) buried 5 cm deep. Plastic barriers were slippery for thatch ants, which could not crawl over the material, but foraging trails were occasionally dug underneath the barriers.
Quantities: 36 enclosures total, 5 m diameter each, 15 cm tall barriers, buried 5 cm deepDuration: Summer 2010 installation, maintained each summer through 2012 by reinstalling barriers and removing bridging vegetationConditions: Montane meadow conditions
Equipment: male fern rhizomes, plastic barriers
Apply nitrogen treatments
Apply elevated N deposition (3.5 times ambient) in half of the ant enclosures. Total N deposition in the meadow was approximately 2 kg N ha⁻¹ year⁻¹ when study began in 2010. Apply 0.5 g N m⁻² of slow-release ammonium nitrate fertilizer once each summer to randomly-selected enclosures (n = 18) to mimic a total N deposition rate of 7 kg N ha⁻¹ year⁻¹.
Quantities: 18 enclosures treated, 0.5 g N m⁻² application rate, targeting 7 kg N ha⁻¹ year⁻¹ total deposition rateDuration: Once each summer from 2010 to 2012Conditions: Applied to randomly-selected enclosures
Equipment: slow-release ammonium nitrate fertilizer
Monitor bear foraging activity
Allow bears to forage on ant nests within the enclosures from 2010 to 2012. Nests were considered inactive if no more than one ant-worker emerged when the ground next to the nest was beaten. Bear attacks on nests and nest inactivity occurred in all three sections of the study meadow and were unrelated to N additions according to binomial models.