D Common Unit Conversions

For many transformations, particularly when automated, please use the udunits2 software where possible. For example, in R, you can use

library(udunits2)
## transform meters to mm
ud.convert(10, "m", "mm")
## equivalently, via the udunits synonym database
ud.convert(10, "meters", "millimeters")
## it can also handle more complex units
ud.convert(10, "m/s", "mm/d")

NB: Many of these conversions have been automated within PEcAn.

Useful conversions for entering site, management, yield, and trait data [To-Do: Fix these!]
From (\(X\)) to (\(Y\)) Conversion Notes
\(X_2=\) root production \(X_1=\) root biomass & root turnover rate \(Y = X_2/X_1\) Gill (2000)
DD\(^{\circ}\) MM’ SS’’ XX.ZZZZ \(\textrm{XX.ZZZZ} = \textrm{DD} + \textrm{MM}/60+\textrm{SS}/3600\) to convert latitude or longitude from degrees, minutes, seconds to decimal degrees
lb kg \(Y=X\times 2.2\)
mm/s \(\mu\) mol CO\(_2\) m\(^{2}\) s\(^{-1}\) \(Y=X\times 0.04\)
m\(^2\) ha \(Y = X/10^6\)
g/m\(^2\) kg/ha \(Y=X\times 10\)
US ton/acre Mg/ha \(Y = X\times 2.24\)
m\(^3\)/ha cm \(Y=X/100\) units used for irrigation and rainfall
% roots root:shoot (q) \(Y=\frac{X}{1-X}\) \(\% \text{roots} = \frac{\text{root biomass}}{\text{total biomass}}\)
\(\mu\) mol cm\(^{-2}\) s\(^{-1}\) mmol m\(^{-2}\) s\(^{-1}\) \(Y = X/10\)
mol m\(^{-2}\) s\(^{-1}\) mmol m\(^{-2}\) s\(^{-1}\) \(Y = X/10^6\)
mol m\(^{-2}\) s\(^{-1}\) \(\mu\) mol cm\(^{-2}\) s\(^{-1}\) \(Y = X/ 10^5\)
mm s\(^{-2}\) mmol m\(^{-3}\) s\(^{-1}\) \(Y=X/41\) Korner et al. [1988]
mg CO\(_2\) g\(^{-1}\) h\(^{-1}\) \(\mu\) mol kg\(^{-1}\) s\(^{-1}\) \(Y = X\times 6.31\) used for root_respiration_rate
\(\mu\) mol mol \(Y= X\times 10^6\)
julian day (1–365) date see https://www-air.larc.nasa.gov/tools/jday.htm (NASA Julian Calendar)
spacing (m) density (plants m\(^{2}\)) \(Y=\frac{1}{\textrm{row spacing}\times\textrm{plant spacing}}\)
kg ha\(^{-1}\) y\(^{-1}\) Mg ha\(^{-1}\) y\(^{-1}\) \(Y= X/1000\)
g m\(^{-2}\) y\(^{-1}\) Mg ha\(^{-1}\) y\(^{-1}\) \(Y= X/100\)
kg mg \(Y=X\times 10^6\)
cm\(^2\) m\(^2\) \(Y=X\times 10^4\)