FOREST ECOLOGY

Nitrogen-fixing trees: Friend or foe?

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Science  01 Sep 2017:
Vol. 357, Issue 6354, pp. 883
DOI: 10.1126/science.357.6354.883-a

Pentaclethra macroloba is a fast-growing nitrogen-fixing tree.

PHOTO: JOAN SIMON/FLICKR

Forest regeneration not only is an important aspect of conservation but also presents a large carbon-capturing potential. Trees that form a symbiotic relationship with nitrogen-fixing bacteria are thought to provide a key reservoir of nitrogen for the surrounding ecosystem, facilitating forest regeneration. However, Taylor et al. report that for tropical rainforests in Costa Rica, this is not the case. They found that plots with more nitrogen-fixing trees had lower overall growth. This study suggests that the benefit of nitrogen input is overshadowed by the suppression of growth caused by fast-growing, resource-depleting, nitrogen-fixing neighbors. More research is needed to identify whether this role of nitrogen-fixing trees as suppressors, rather than facilitators, is relevant in forest regeneration more widely.

Proc. Natl. Acad. Sci. U.S.A. 10.1073/pnas.1707094114 (2017).

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