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Ectomycorrhizal impacts on plant nitrogen nutrition: emerging isotopic patterns, latitudinal variation and hidden mechanisms
Author(s) -
Mayor Jordan,
Bahram Mohammad,
Henkel Terry,
Buegger Franz,
Pritsch Karin,
Tedersoo Leho
Publication year - 2015
Publication title -
ecology letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 6.852
H-Index - 265
eISSN - 1461-0248
pISSN - 1461-023X
DOI - 10.1111/ele.12377
Subject(s) - ecosystem , biogeochemical cycle , tropics , ecology , nitrogen cycle , terrestrial ecosystem , latitude , productivity , environmental science , nutrient cycle , isotopes of nitrogen , nutrient , ectomycorrhiza , cycling , biogeochemistry , biology , nitrogen , mycorrhiza , symbiosis , chemistry , geography , genetics , macroeconomics , organic chemistry , geodesy , archaeology , bacteria , economics
Ectomycorrhizal (EcM)‐mediated nitrogen (N) acquisition is one main strategy used by terrestrial plants to facilitate growth. Measurements of natural abundance nitrogen isotope ratios (denoted as δ 15 N relative to a standard) increasingly serve as integrative proxies for mycorrhiza‐mediated N acquisition due to biological fractionation processes that alter 15 N: 14 N ratios. Current understanding of these processes is based on studies from high‐latitude ecosystems where plant productivity is largely limited by N availability. Much less is known about the cause and utility of ecosystem δ 15 N patterns in the tropics. Using structural equation models, model selection and isotope mass balance we assessed relationships among co‐occurring soil, mycorrhizal plants and fungal N pools measured from 40 high‐ and 9 low‐latitude ecosystems. At low latitudes 15 N‐enrichment caused ecosystem components to significantly deviate from those in higher latitudes. Collectively, δ 15 N patterns suggested reduced N‐dependency and unique sources of EcM 15 N‐enrichment under conditions of high N availability typical of the tropics. Understanding the role of mycorrhizae in global N cycles will require reevaluation of high‐latitude perspectives on fractionation sources that structure ecosystem δ 15 N patterns, as well as better integration of EcM function with biogeochemical theories pertaining to climate‐nutrient cycling relationships.