User:Davidlburton/sandbox

Nitrate Exposure (NE) is a measure of the exposure of the soil microbial community to nitrate. It is an extensive variable with units of concentration-days (g N d/kg), which integrates nitrate concentration over time, reflecting the influence of nitrate on soil biological processes over time, supporting growth, poising the redox and influencing gene expression. NE is often calculated from composite samples that also integrate nitrate concentration over space. Expressing the presence of nitrate as a variable integrated over both time and space provides the opportunity to explore the longer-term, spatially integrated influence of nitrate on soil biological processes. This represents not only the role of nitrate as a substrate, but also its influence on redox condition and indirect effects on gene expression that are reflected over the longer term. Nitrate Exposure(NE) is calculated as the integral of nitrate concentration over time according to equation:

$$NE = \sum_{i=1}^N[{NO_3}^-]_i*\left ( \frac{d_{i+1}+d_{i-1}}{2} \right)$$

Where [NO3-]i is the concentration of NO3- (g N/kg soil) measured on ith event, di is the date of the ith event (days) integrated over N events. NE has the units of concentration-days (e.g., g N d kg-1 soil).