Summary of the article on the Cost of Nitrogen Fixation:

**Cost of Nitrogen Fixation**

The article discusses the cost of nitrogen fixation, which is derived from the work of Houlton et al. (2008). The cost of fixation is represented by the following equation:

\\[N\_{cost,fix} = -s\_{fix}/(1.25 e^{a\_{fix} + b\_{fix} . t\_{soil} (1 - 0.5 t\_{soil}/ c\_{fix}) })\\\]

Where:
- \\(a\_{fix}\\), \\(b\_{fix}\\) and \\(c\_{fix}\\) are parameters of the temperature response function of fixation, as reported by Houlton et al. (2008)
- \\(t\_{soil}\\) is the soil temperature in degrees Celsius
- The values of the parameters are fitted to empirical data: \\(a=-3.62 \pm 0.52\\), \\(b=0.27 \pm 0.04\\), and \\(c=25.15 \pm 0.66\\)
- The factor of 1.25 converts the temperature response function to a 0-1 limitation factor, as employed by Houlton et al.
- The function represents the rate of uptake for a given temperature, which is then assimilated into the cost term by assuming the rate is analogous to a conductance for nitrogen and inverting the term to produce a cost/resistance analogue.
- The temperature-limited cost is then calculated by multiplying the temperature term by the minimum cost at optimal temperature (\\(s\_{fix}\\)), resulting in a cost in terms of carbon to nitrogen ratios.