Nitrogen deposition and vegetation change in six Canadian national parks

Koechy, M., and S. D. Wilson (1997)

Rapid vegetation changes in parks in agro-industrial landscapes may be partly due to increased atmospheric nitrogen deposition. To test this hypothesis, we measured atmospheric N deposition and soil available N in six western Canadian national parks, three of which were in agro-industrial landscape and three surrounded by more natural landscape. Deposition was continuously collected by ion-exchange resin bags on the soil surface outside the existing forest canopy. Soil available N was collected by buried resin bags. Bags were replaced four times a year for two years. N deposition was higher in parks in agro-industrial landscape (6.2 mg m^-2 d^-1) than in natural landscape (3.6 mg m^-2 d^-1) but the difference was not significant because one park in natural landscape also received high loads of atmospheric N (5.0 mg mm^-2 d^-1), probably from long-distance transport. Soil available N differed significantly among parks but not between agro-industrial and natural landscapes (1.7 µg bag m^-2 d^-1). Soil available N increased significantly with N deposition, suggesting that ecosystem N fluxes have increased due to N deposition.