@article {1333354,
	title = {Nitrogen-fixing tree abundance in higher-latitude North America is not constrained by diversity},
	journal = {Ecology Letters},
	volume = {20},
	year = {2017},
	pages = {842-851},
	abstract = {The rarity of nitrogen (N)-fixing trees in frequently N-limited higher-latitude (here, \&gt;\&nbsp;35{\textdegree}) forests is a central biogeochemical paradox. One hypothesis for their rarity is that evolutionary constraints limit N-fixing tree diversity, preventing N-fixing species from filling available niches in higher-latitude forests. Here, we test this hypothesis using data from the USA and Mexico. N-fixing trees comprise only a slightly smaller fraction of taxa at higher vs. lower latitudes (8\% vs. 11\% of genera), despite 11-fold lower abundance (1.2\% vs. 12.7\% of basal area). Furthermore, N-fixing trees are abundant but belong to few species on tropical islands, suggesting that low absolute diversity does not limit their abundance. Rhizobial taxa dominate N-fixing tree richness at lower latitudes, whereas actinorhizal species do at higher latitudes. Our results suggest that low diversity does not explain N-fixing trees{\textquoteright} rarity in higher-latitude forests. Therefore, N limitation in higher-latitude forests likely results from ecological constraints on N fixation.},
	url = {https://onlinelibrary.wiley.com/doi/abs/10.1111/ele.12778},
	author = {Duncan N.L. Menge and Sarah A. Batterman and Wenying Liao and Benton N. Taylor and Jeremy W. Lichstein and Gregorio Angeles-Perez}
}
