Data from: Disentangling the variability of symbiotic nitrogen fixation rate and the controlling factors
Data files
Apr 24, 2024 version files 106.27 KB
Abstract
Symbiotic nitrogen (N) fixation (SNF), replenishing bioavailable N for terrestrial ecosystems, exerts decisive roles in N cycling and gross primary production. Nevertheless, it remains unclear what determines the variability of SNF rate, which retards the accurate prediction for global N fixation in earth system models. This study synthesized 1230 isotopic observations to elucidate the governing factors underlying the variations of SNF rate. The SNF rates varied significantly from 3.69 to 12.54 g N m-2 yr-1 across host plant taxa. The traits of host plant (e.g., biomass characteristics and taxa) far outweighed soil properties and climatic factors in explaining the variations of SNF rate, accounting for 79.0% of total relative importance. Furthermore, annual SNF yield contributed to more than half of N uptake for host plants, which was consistent across different ecosystem types. This study highlights that the biotic factors, especially host plant traits (e.g., biomass characteristics and taxa), play overriding roles in determining SNF rate compared with soil properties. The suite of parameters for SNF lend support to improve N fixation module in earth system models that can provide more confidence in predicting bioavailable N changes in terrestrial ecosystems.
README
The peer-reviewed papers for this synthesis were searched up to September 7, 2022, using Web of Science and China National Knowledge Infrastructure Database. The SNF data were from the field measurements. The strings employed for searching papers are: ((“nitrogen fixation” or “N fixation” or “N2 fixation” or “dinitrogen fixation” or “nitrogenase”) and field). The following criteria were used to sift out the peer-reviewed papers: 1.The SNF rate was measured using 15N isotope method (e.g., 15N natural abundance, and 15N dilution) since these methods guarantee the accuracy of SNF across large spatial/temporal scale than acetylene reduction assay method (Davies-Barnard et al., 2020; Soper et al., 2021); 2. The measurement must be given the unambiguous unit; 3. The studies that plant has been inoculated with specific strains of bacteria (e.g., rhizobium) were excluded; 4. The SNF was measured in the field rather than the laboratory incubation or greenhouse cultivation, and the data from aqueous environments (e.g., river or lake sediments) were excluded.
The SNF rate, host plant taxa, biomass traits (i.e., the biomass of shoot, grain, and root), and soil properties (i.e., clay contents, bulk density, pH, cation exchange capacity, organic carbon, N and phosphorus contents, carbon:N ratio, and carbon:phosphorus ratio) were directly extracted from tables or graphs in peer-reviewed papers using GetData software. Climatic variables (i.e., mean annual temperature and precipitation) and soil microbial traits (i.e., carbon:N and carbon:phosphorus ratio of soil microbial biomass) were obtained from the climatic database (http://www.worldclim.org) (Fick et al., 2017) and soil microbial biomass dataset (Wang et al., 2022), respectively, according to the geographical information.
Methods
The peer-reviewed papers for this synthesis were searched up to September 7, 2022, using Web of Science and China National Knowledge Infrastructure Database. The SNF data were from the field measurements. The strings employed for searching papers are: ((“nitrogen fixation” or “N fixation” or “N2 fixation” or “dinitrogen fixation” or “nitrogenase”) and field). The following criteria were used to sift out the peer-reviewed papers: 1. The SNF rate was measured using 15N isotope method (e.g., 15N natural abundance, and 15N dilution) since these methods guarantee the accuracy of SNF across large spatial/temporal scale than acetylene reduction assay method (Davies-Barnard et al., 2020; Soper et al., 2021); 2. The measurement must be given the unambiguous unit; 3. The studies that plant has been inoculated with specific strains of bacteria (e.g., rhizobium) were excluded; 4. The SNF was measured in the field rather than the laboratory incubation or greenhouse cultivation, and the data from aqueous environments (e.g., river or lake sediments) were excluded. Finally, 112 peer-reviewed papers were eligible for the construction of SNF dataset.