Premium
Molybdenum and phosphorus limitation of moss‐associated nitrogen fixation in boreal ecosystems
Author(s) -
Rousk Kathrin,
Degboe Jefferson,
Michelsen Anders,
Bradley Robert,
Bellenger JeanPhilippe
Publication year - 2017
Publication title -
new phytologist
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 3.742
H-Index - 244
eISSN - 1469-8137
pISSN - 0028-646X
DOI - 10.1111/nph.14331
Subject(s) - tundra , subarctic climate , moss , taiga , ecosystem , nitrogen fixation , nitrogenase , boreal , biomass (ecology) , growing season , black spruce , environmental chemistry , ecology , nutrient , environmental science , botany , nitrogen , biology , chemistry , organic chemistry
Summary Biological nitrogen fixation ( BNF ) performed by moss‐associated cyanobacteria is one of the main sources of new nitrogen (N) input in pristine, high‐latitude ecosystems. Yet, the nutrients that limit BNF remain elusive. Here, we tested whether this important ecosystem function is limited by the availability of molybdenum (Mo), phosphorus (P), or both. BNF in dominant mosses was measured with the acetylene reduction assay ( ARA ) at different time intervals following Mo and P additions, in both laboratory microcosms with mosses from a boreal spruce forest and field plots in subarctic tundra. We further used a 15 N 2 tracer technique to assess the ARA to N 2 fixation conversion ratios at our subarctic site. BNF was up to four‐fold higher shortly after the addition of Mo, in both the laboratory and field experiments. A similar positive response to Mo was found in moss colonizing cyanobacterial biomass. As the growing season progressed, nitrogenase activity became progressively more P limited. The ARA : 15 N 2 ratios increased with increasing Mo additions. These findings show that N 2 fixation activity as well as cyanobacterial biomass in dominant feather mosses from boreal forests and subarctic tundra are limited by Mo availability.