Such global N enrichment has
profoundly altered biogeochemical cycles in both aquatic and
terrestrial biospheres (Gruber and Galloway, 2008). N is often the
most limiting nutrient for plant growth (Vitousek and Howarth,
1991; LeBauer and Treseder, 2008). Plant growth and productivity
generally increased with the increase of N deposition across various
terrestrial plant species and ecosystems (Elser et al., 2007; Xia and
Wan, 2008). T