Tree-ring N isotopic ratio increased with increasing latitude and decreasing N availability in pine stands across Finland

•N deposition in 1951–2020 totaled 120–470 kg/ha, i.e., annual average 1.8–6.7 kg/ha.•Soils in pine stands were similar, except decreasing N status with the lowest deposition.•Tree ring δ15N was different between the lowest and highest N deposition sites.•δ15N in 1951–2020 correlated negatively with total-, ammonium- and nitrate-N depositions.•Temporal development of δ15N and N deposition coincided only on some sites.