Facultative nitrogen fixation by canopy legumes in a lowland tropical forest

Autor: Alexander R. Barron, Lars O. Hedin, Drew W. Purves
Rok vydání: 2010
Předmět:
Zdroj: Oecologia. 165:511-520
ISSN: 1432-1939
0029-8549
DOI: 10.1007/s00442-010-1838-3
Popis: Symbiotic dinitrogen (N(2)) fixation is often invoked to explain the N richness of tropical forests as ostensibly N(2)-fixing trees can be a major component of the community. Such arguments assume N(2) fixers are fixing N when present. However, in laboratory experiments, legumes consistently reduce N(2) fixation in response to increased soil N availability. These contrasting views of N(2) fixation as either obligate or facultative have drastically different implications for the N cycle of tropical forests. We tested these models by directly measuring N(2)-fixing root nodules and nitrogenase activity of individual canopy-dominant legume trees (Inga sp.) across several lowland forest types. Fixation was substantial in disturbed forests and some gaps but near zero in the high N soils of mature forest. Our findings suggest that canopy legumes closely regulate N(2) fixation, leading to large variations in N inputs across the landscape, and low symbiotic fixation in mature forests despite abundant legumes.
Databáze: OpenAIRE
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