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 \label{tab:conversions}

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{XX} + \textrm{MM}/60+\textrm{SS}/60)

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 ref: http://disc.gsfc.nasa.gov/julian_calendar.shtml (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)