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Phosphatase activity and nitrogen fixation reflect species differences, not nutrient trading or nutrient balance, across tropical rainforest trees
Author(s) -
Batterman Sarah A.,
Hall Jefferson S.,
Turner Benjamin L.,
Hedin Lars O.,
LaHaela Walter J. Kimiko,
Sheldon Pete,
Breugel Michiel
Publication year - 2018
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.13129
Subject(s) - nutrient , biogeochemical cycle , nitrogen , tropical rainforest , phosphorus , nitrogen fixation , rainforest , ecology , sink (geography) , biology , biogeochemistry , carbon sink , environmental science , ecosystem , agronomy , chemistry , geography , cartography , organic chemistry
Abstract A fundamental biogeochemical paradox is that nitrogen‐rich tropical forests contain abundant nitrogen‐fixing trees, which support a globally significant tropical carbon sink. One explanation for this pattern holds that nitrogen‐fixing trees can overcome phosphorus limitation in tropical forests by synthesizing phosphatase enzymes to acquire soil organic phosphorus, but empirical evidence remains scarce. We evaluated whether nitrogen fixation and phosphatase activity are linked across 97 trees from seven species, and tested two hypotheses for explaining investment in nutrient strategies: trading nitrogen‐for‐phosphorus or balancing nutrient demand. Both strategies varied across species but were not explained by nitrogen‐for‐phosphorus trading or nutrient balance. This indicates that (1) studies of these nutrient strategies require broad sampling within and across species, (2) factors other than nutrient trading must be invoked to resolve the paradox of tropical nitrogen fixation, and (3) nitrogen‐fixing trees cannot provide a positive nitrogen‐phosphorus‐carbon feedback to alleviate nutrient limitation of the tropical carbon sink.