Ecological interpretations of nitrogen isotope ratios of terrestrial plants and soils

• DOI: 10.1007/s11104-015-2542-1
• Publication Date: 2015-06-11T06:03:53Z
• Authors: Joseph M. Craine; E. N. J. Brookshire; Michael D. Cramer; Niles J. Hasselquist; Keisuke Koba; Erika Marin-Spiotta; Lixin Wang
• Keywords: Terrestrial ecosystem; Terrestrial plant; Isotopes of nitrogen; Cycling

Background Knowledge of biological and climatic controls in terrestrial nitrogen (N) cycling within and across ecosystems iscentral tounderstandingglobalpatternsof keyecosystemprocesses.Theratiosof 15 N: 14 Ninplants and soils have been used as indirect indices of N cycling parameters, yet our understanding of controls over N isotope ratios in plants and soils is still developing. Scope In this review, we provide background on the mainprocessesthataffectplantandsoilNisotoperatios. In a similar manner to partitioning the roles of state factors and interactive controls in determining ecosystem traits, we review N isotopes patterns in plants and soils across a number of proximal factors that influence ecosystem properties as well as mechanisms that affect these patterns. Lastly, some remaining questions that would improve our understanding of N isotopes in terrestrial ecosystems are highlighted. Conclusion Compared to a decade ago, the global patterns of plant and soil N isotope ratios are more resolved. Additionally, we better understand how plant and soil N isotope ratios are affected by such factors as mycorrhizal fungi, climate, and microbial processing. A comprehensive understanding of the N cycle that ascribes different degrees of isotopic fractionation for each step under different conditions is closer to being realized, but a number of process-level questions still remain.