Ecological Archives E094-064-A2

Stephanie Yelenik, Steven Perakis, David Hibbs. 2013. Regional constraints to biological nitrogen fixation in post-fire forest communities. Ecology 94:739–750. http://dx.doi.org/10.1890/12-0278.1

Appendix B. Supplementary results: asymbiotic N-fixation rates recalculated with a range of published conversion factors, forest floor and soil ARA rates, and N-mineralization rates.

Table B1. Published 15N2 calibrated ARA conversion rates (Acetylene fixed: Nitrogen fixed, mol:mol) for soil and litter (forest floor) and the corresponding across-site average for N-fixation rates given ARA data from the Klamath National Forest. Rates presented in this manuscript using the theoretical conversion rate of 4 are shown in the final, shaded row for comparison.

ARA: 15N2
conversion
Sample
material
Sample
species/habitat
Source Soil N-
fixation rates
(kg N ha-1 yr-1)
Litter/forest floor
N-fixation rates
(kg N ha-1 yr-1)
3.45 litter Metrocideros
polymorpha
(Ley and D'Antonio 1998)   0.09
3.52 litter Pseudotsuga
menziesii
(Heath et al. 1988)   0.09
3.69 litter Pseudotsuga
menziesii
(Silvester 1989)   0.09
3.9 litter Metrocideros
polymorpha
(Crews et al. 2000,
Reed et al. 2007)
  0.08
13.3 litter Dodonea viscosa (Ley and D'Antonio 1998)   0.02
1.34 soil Woodland/grassland (Ley and D'Antonio 1998) 2.5  
8.6 soil Agriculture/fallow fields (Hardy et al. 1973) 0.4  
4 litter, soil Theoretical
conversion rate
(Hardy et al. 1968) 0.8 0.08

FigB1

Fig. B1. Relationships between the proportional increase in forest floor acetylene reduction rates (ARA) due to phosphorus (P) fertilizer addition and background concentrations (i.e., control plot data only) of (A) forest floor P and (B) soil P (i.e., control plot data only). Relationships between control rates of forest floor ARA and forest floor (C) phosphorus, (D) carbon, and (E) nitrogen. Data points represent means for each of 6 sites. Note that ARA rates are converted to BNF using forest floor biomass or soil bulk density, and ARA conversion rates. Because we did not vary soil bulk density or conversion rates by site, relative differences between sites are the same for soil ARA and BNF. In contrast, relative differences between sites may vary between forest floor BNF and ARA due to site level variation in forest floor biomass.


FigB2

Fig. B2. Relationships between the proportional increase in soil acetylene reduction rates (ARA) due to phosphorus (P) fertilizer addition and background concentrations (i.e., control plot data only) of (A) soil Bray-P and (B) soil total dissolved nitrogen: total dissolved phosphorus (TDN:TDP). Relationships between control rates of soil ARA and soil (C) Bray-P, (D) % Carbon, and (E) net N mineralization. Data points represent means for each of 6 sites.


FigB3

Fig. B3. The relationship between potential net N mineralization rates and (A) Ceanothus biomass and (B) Ceanothus N-fixation rates. Data points represent means for each of 6 sites.


 

Literature cited

Crews, T. E., H. Farrington, and P. M. Vitousek. 2000. Changes in asymbiotic, heterotrophic nitrogen fixation on leaf litter of Metrosideros polymorpha with long-term ecosystem development in Hawaii. Ecosystems 3:386–395.

Hardy, R. W. F., R. C. Burns, and R. D. Holsten. 1973. Applications of the acetylene-ethylene assay for measurement of nitrogen fixation. Soil Biology and Biochemistry 5:47–81.

Hardy, R. W. F., R. D. Holsten, E. K. Jackson, and R. C. Burns. 1968. The acetylene-ethylene assay for N2 fixation: laboratory and field evaluation. Plant Physiology 43:1185–1207.

Heath, B., P. Sollins, D. A. Perry, and K. Cromack Jr. 1988. Asymbiotic nitrogen fixation in litter from Pacific Northwest forests. Canadian Journal of Forest Research 18:68–74.

Ley, R. E., and C. M. D'Antonio. 1998. Exotic grass invasion alters potential rates of N fixation in Hawaiian woodlands. Oecologia 113:179–187.

Reed, S. C., C. C. Cleveland, and A. R. Townsend. 2007. Controls over leaf litter and soil nitrogen fixation in two lowland tropical rain forests. Biotropica 39:585–592.

Silvester, W. B. 1989. Molybdenum limitation of asymbiotic nitrogen fixation in forests of Pacific Northwest America. Soil Biology and Biochemistry 21:283–289.


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