Data for: Tree symbioses sustain nitrogen fixation despite excess nitrogen supply

Symbiotic nitrogen fixation (SNF) is a key ecological process whose impact depends on the strategy of SNF regulation – the degree to which rates of SNF change in response to limitation by N vs. other resources. SNF that is obligate or exhibits incomplete down-regulation can result in excess N fixation, whereas a facultative SNF strategy does not. We hypothesized that tree-based SNF strategies differed by latitude (tropical vs temperate) and symbiotic type (actinorhizal vs rhizobial). Specifically, we expected tropical rhizobial symbioses to display strongly facultative SNF as an explanation for their success in low-latitude forests. In this study, we used 15N isotope dilution field experiments in New York, Oregon, and Hawaii to determine SNF strategies in six N-fixing tree symbioses. Nitrogen fertilization with +10 and +15 g N m-2 y-1 for 4-5 years alleviated N limitation in all taxa, paving the way to determine SNF strategies. Contrary to our hypothesis, all six of the symbioses we stu..., See paper., The data files are .csv files, so they can be opened in many programs. For example, Excel.
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