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How to Calculate the Climate Decomposition Index (CDI)

A CDI is a multiplicative function that describes the effect of monthly variation in temperature and water on decomposition. The water function assumes that water controls decomposition primarily through water stress.  Thus, extremely high levels of soil moisture (e.g., waterlogged soils) may not be well represented by these CDIs.  Annual CDIs are the mean value of monthly CDIi's, which are calculated as a function of mean monthly air temperature (Ti), monthly precipitation (PPTi), and monthly PETi of the ith month:


 In Adair et al. (2008), multiple temperature equations were compared using the Long-term Intersite Decomposition Experiment Team (LIDET) data set. For this data set, the best equation was the Lloyd and Taylor (1994) variable Q10 temperature function (shown above as FT(Ti)).

CDI may be calculated using monthly precipitation and temperature data. If climate data are not available, it is possible to use simulated data  from CRU.

Two options are available for calculating CDI (excel files):

CDI using the Lloyd and Taylor (1994) temperature function

CDI using an arctangent temperature function (Del Grosso et al. 2005)

Please feel free to contact me (adair(at)nceas(dot)ucsb(dot)edu) with questions.

Banner photo: Mt. Massive in Colorado, 2009