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15 N IN SYMBIOTIC FUNGI AND PLANTS ESTIMATES NITROGEN AND CARBON FLUX RATES IN ARCTIC TUNDRA
Author(s) -
Hobbie John E.,
Hobbie Erik A.
Publication year - 2006
Publication title -
ecology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.144
H-Index - 294
eISSN - 1939-9170
pISSN - 0012-9658
DOI - 10.1890/0012-9658(2006)87[816:nisfap]2.0.co;2
Subject(s) - tundra , nitrogen cycle , nitrogen , terrestrial ecosystem , nutrient , terrestrial plant , ecosystem , environmental science , botany , ecology , biology , chemistry , organic chemistry
When soil nitrogen is in short supply, most terrestrial plants form symbioses with fungi (mycorrhizae): hyphae take up soil nitrogen, transport it into plant roots, and receive plant sugars in return. In ecosystems, the transfers within the pathway fractionate nitrogen isotopes so that the natural abundance of 15 N in fungi differs from that in their host plants by as much as 12‰. Here we present a new method to quantify carbon and nitrogen fluxes in the symbiosis based on the fractionation against 15 N during transfer of nitrogen from fungi to plant roots. We tested this method, which is based on the mass balance of 15 N, with data from arctic Alaska where the nitrogen cycle is well studied. Mycorrhizal fungi provided 61 – 86% of the nitrogen in plants; plants provided 8 – 17% of their photosynthetic carbon to the fungi for growth and respiration. This method of analysis avoids the disturbance of the soil – microbe – root relationship caused by collecting samples, mixing the soil, or changing substrate concentrations. This analytical technique also can be applied to other nitrogen‐limited ecosystems, such as many temperate and boreal forests, to quantify the importance for terrestrial carbon and nitrogen cycling of nutrient transfers mediated by mycorrhizae at the plant – soil interface.