Reply to: Data do not support large-scale oligotrophication of terrestrial ecosystems

CRAINE J., ELMORE A., WANG L., BOECKX P., DELZON S., FANG Y., GRAY A., GUERRIERI R., GUNDALE M., HIETZ P., NELSON D., PERI P.L., TEMPLER P., WERNER C.

Nature Ecology and Evolution

Springer Nature Publishing

Año: 2019 vol. 3 p. 1287 - 1288

There are many reasons that the isotopic signature of deposited N is unlikely to be causing the declines in plant δ15N. Although our analysis of foliar δ15N was limited to after 1980, declines in foliar, tree-ring and sediment δ15N pre-date the onset of widespread inorganic N fertilizer use, as well as any timing ofshifts to more reduced forms of N in deposition. Also, despite variation in the isotopic signatures of N deposition and its sources, there is no evidence currently that the signature of atmospheric N deposition has been declining overtime. A global, comprehensive dataset on the signature of N deposition does not exist and would be helpful to generate. Yet, even if the isotopic signature of N deposition has been declining, changes in N availability can have a stronger influence on plant δ15N than the signature of added N.