Fire affects asymbiotic nitrogen fixation in southern Amazon forests

Published: 01-03-2020| Version 2 | DOI: 10.17632/x4ytsfd2g2.2
Barbara Bomfim,
Lucas Silva,
Ben Hur Marimon Junior,
Beatriz Marimon,
Timothy Doane,
William Horwath


In this study, we investigate the biogeochemical consequences of fire in seasonally flooded Amazon forests, where recent declines in forest cover have been linked to increases in fire frequency and severity. Previous studies have hypothesized that a quasi‐permanent state‐shift transition from typical Amazon forests to open savannas can occur when fire results in further depletion of already impoverished soil nutrient pools. Asymbiotic N2 fixation (ANF) is an essential pathway for fire‐affected forests to acquire nitrogen (N) after disturbance, but ANF response to fire has yet to be quantified in Amazonia. Here, we quantify ANF through field sampling and laboratory incubations using 15N‐labeled dinitrogen (15N2) and measurement of 14 biogeochemical parameters in surface (0–10 cm) and subsurface (10–30 cm) soils. Our data represent burned and unburned replicated sampling sites, across five stands, spanning a gradient from infrequent (once in 13 years) to frequent (five times in 13 years) fire occurrences. Biogeochemical variables (asymbiotic N fixation, total C, total N, total P, total Fe, Mehlich-3 P, Mehlich-3 Fe, potentially mineralizable N, pH, and gravimetric water content) of soils collected in burned and unburned areas within five seasonally flooded forests in the southern portion of Brazilian Amazonia. Soils were collected in July 2016 and hand-carried immediately for the University of California, Davis, where all the laboratory work was conducted. The document "Bomfim et al. SI" provides all the information regarding the soil data.


Steps to reproduce

All the information related to the laboratory analyses are described in Bomfim et al. (2020)-- link provided below.