Canopy 15N fertilization increases short-term plant N retention compared to ground fertilization in an oak forest
Luca Da Ros, Mirco Rodeghiero, Christine L. Goodale, Gregor Trafoier, Pietro Panzacchi, Francesco Giammarchi, Giustino Tonon, Maurizio Ventura
Abstract
The effects of atmospheric nitrogen (N) deposition on forests ecosystems depend on the fate of N in the ecosystem, and the role of tree canopy in intercepting, transforming, and assimilating atmospheric N inputs. In this study, increased in N deposition was simulated with the application of N fertilizer with two contrasting strategies: above and below the canopy, in a sessile oak (Quercus petraea (Matt.) Liebl.) stand. Three weeks after the labeled fertilization, more than twice as much fertilizer was recovered in plants in the above-canopy application (12 ± 5 %), than in the below-canopy application (5 ± 2 %). By contrast, the litter layer on the forest floor retained more fertilizer in the below-canopy (37 ± 8%) than in the above-canopy (7 ± 5 %) application. Seven months later, more fertilizer was recovered in wood and fine roots in below-canopy (8 ± 1 %) than in above-canopy (4 ± 1 %) fertilization. Wood recovery was higher in the below-canopy (6.7 ± 2.7 % vs 3.6 ± 0.6 % in the above-canopy). This experiment shows that fertilization approach alters the short-term fate of the added N in a broadleaved forest, highlighting the importance of the forest canopy in intercepting atmospheric N deposition also in these widely represented forests.