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CDI
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 CDI_{i}'s, which are
calculated as a function of mean monthly air temperature (T_{i}),
monthly
precipitation
(PPT_{i}),
and monthly PET_{i}
of the i^{th} month:
In Adair et al. (2008), multiple
temperature equations were compared using the Longterm
Intersite
Decomposition
Experiment Team (LIDET)
data set. For this data set, the best equation was the Lloyd and Taylor
(1994) variable Q_{10} temperature function (shown above as F_{T}(T_{i})).
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. 


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photo: Mt. Massive in Colorado, 2009
