Ecological risks in anthropogenic disturbance of nitrogen cycles in natural terrestrial ecosystems

• Published in: Ecological research 2009-09, Vol.24 (5), p.955-964
• Main Authors: Fujimaki, Reiji, Sakai, Akiko, Kaneko, Nobuhiro
• Format: Article
• Language: English
• Subjects: Anthropogenic factors; Behavioral Sciences; Biomedical and Life Sciences; Biosphere; Ecology; Ecosystem management; Environmental impact; Evolutionary Biology; Forest ecosystem; Forest management; Forestry; Forests; Grasslands; Herbivory; Human influences; Introduced plants; Introduced species; Land use; Life Sciences; Nitrogen; Nitrogen saturation; Nutrient balance; Nutrient cycles; Plant communities; Plant populations; Plant Sciences; Plant species; Rare species; Reactive nitrogen (Nr); Risk management; Saturation; Special Feature; Species extinction; Terrestrial ecosystems; Terrestrial environments; Translocation; Vegetation change; Zoology
• ISSN: 0912-3814; 1440-1703
• DOI: 10.1007/s11284-008-0578-x

Anthropogenic addition of reactive nitrogen (Nr) to the biosphere is increasing globally and some terrestrial ecosystems are suffering from a state of excess Nr for biological nitrogen (N) demand, termed N saturation. Here, we review the ecological risks in relation to N saturation and prospective responses to N saturation. Excess Nr increases the risks of local extinction of rare plant species, encouragement of exotic plant species, disturbance of nutrient balance in plant organs, and increase of herbivory in plant communities. On the ecosystem scale, excess bioavailable N induces forest decline, disturbance of nutrient cycling within ecosystems, depending on vegetation, soil, land-use, and N-loading history. These Nr risks will increase in the Asian region, where impacts of Nr in natural terrestrial ecosystems have been scarcely studied. Whether much of the terrestrial ecosystems on a global level are in the sate of N saturation or not is still controversial, but the potential risks of excess Nr seem to be increasing. The fundamental ways to mitigate Nr risks are to reduce Nr production, prevent Nr translocation, and promote conversion of Nr to N 2 . Temporal, but promising actions against ecological N risks may include management of forests and riparian zones, and carbon addition in grassland.