Spatial distribution of percent cover data for Calluna vulgaris from two example quadrats over the course of the experiment. The upper panels show the cover of Calluna vulgaris for each survey year for a quadrat at 16 m from the NH\({}_{3}\) fumigation source, receiving approximately 6 g N m\({}^{-2}\) y\({}^{-1}\). After five years of treatment, no living Calluna vulgaris remained in the quadrat. The lower panels show the cover of Calluna vulgaris for each survey year for a quadrat at 32 m from the NH\({}_{3}\) fumigation source, receiving approximately 3 g N m\({}^{-2}\) y\({}^{-1}\). Here, living Calluna vulgaris has markedly declined, but some living fraction remains after 13 years.