Shoot increment of Calluna is the most sensitive indicator for N fertilisation.

Cryptogam tissue C:N ratios responded to N inputs ≥5 kg ha⁻¹ yr⁻¹ after 3 years.

Shifts in species cover occurred after 3 years of N inputs ≥10 kg ha⁻¹ yr⁻¹.

C:N ratios of the mineral soil were inappropriate indicators for N inputs.

Dwarf shrub growth suggests ecosystem sensitivity even to low but chronic N inputs.