# 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. 
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$$^2$$ $$Y=X\times 10^4$$