Phosphorus controls symbiotic nitrogen fixation in fire-dependent longleaf pine savannas

Symbiotic nitrogen (N) fixation has the potential to replenish fire-induced N losses in frequently burned ecosystems. A strong relationship between fire and fixation may exist because fire volatilizes N and mineralizes phosphorus (P), creating N-poor, P-rich soils that favor plants capable of N-fixation. However, human activities have enriched ecosystems with N, which may complicate the interplay among fire, fixation, and soil P. We evaluated how N and P modulate the relationship between fire and symbiotic N fixation in longleaf pine savannas, where it was previously documented that N fixation fails to replenish N losses from fire. Across gradients of stand age and fire frequency, we investigated how N and P availability influence fixation, and we established a nutrient addition experiment to evaluate the effects of N and P on legume growth, fixation, and mycorrhizal investment. We uncovered a clear signal of P limitation of herbaceous legumes. Legume growth and fixation were linked to ..., Study site         
We conducted this research at Fort Moore Military Installation in southwestern Georgia (previously known as Fort Benning, and hereafter referred to as Moore) and Eglin Air Force Base in northwestern Florida (hereafter, Eglin), which respectively represent the Fall-Line and Coastal Plain ranges of sandhill longleaf pine savanna ecosystems (Peet, 2006). We received permission to conduct fieldwork through contract RC-2328 with the Strategic Environmental Research and Development Program. The climate at both sites is humid subtropical, and precipitation occurs throughout the year with a wetter season from May to September (MAT = 18.0˚ and 18.7˚C and MAP = 1,260 and 1,802 mm at Moore and Eglin, respectively).
Both military installations were acquired by the Department of Defense in the 1930s and have a mixed history of land use including agriculture, silviculture, grazing, and fire exclusion (Frost, 1993; Rodgers & Provencher, 1999), but now support large tracts of l..., , # Phosphorus controls symbiotic nitrogen fixation in fire-dependent longleaf pine savannas

[https://doi.org/10.5061/dryad.gmsbcc2x1](https://doi.org/10.5061/dryad.gmsbcc2x1)

## Description of the data and file structure

**plot_data.csv**

A CSV including estimates of symbiotic N fixation by herbaceous legumes (n_fix; kg N ha^-1), phosphorus availability as determined by anion resins (resin_p; ppm), net N mineralization (net_nmin; kg N ha-1 year-1), soil leucyl aminopeptidase activity (lap; nmol gsoil^-1 hour^-1), and soil acid phosphatase activity (ap; nmol gsoil^-1 hour^-1) at each plot (plot_id; n = 54) at Eglin and Benning (site). The variables of time since fire (days_since_burn at the time of sampling for soil phosphorus availability), fire return interval (fri; years^-1), and stand age (stand_age; years) are also included.  NA values for fri indicate that there had been no fire events since the establishment of the longleaf pine plantation.

**legume_treatment_responses.csv**
...