[R-sig-ME] nested two level mixed model with lmer

Cristina Muschitiello muschitiello at gmail.com
Tue Jun 14 11:14:45 CEST 2016

I'd need to have a suggestion for my analysis:

I have two soil treatments: CT and NT.

For each treatment, I have 11 CO2 measurements taken in 7 times, i.e. 11
"replicates" for 7 dates.
Replicates are nested in the treatments.

I'd like to evaluate if the measurements are different in time for the two

My information are:

   - replicates(11)=random factor;
   - days=repeated measure factor (fixed factor)
   - treatment = between subject factor (fixed factor)
   - CO2 = Co2 emission measures (=dependent variable)

Is it correct to consider this as a nested two-level repeated measures

Is it correct to use the following R sintax?

m1 <- lmer(CO2~days*treatment+(days|replicates),mydata)

Is this a random intercept and slope model with replicates nested in

Is it correct to say that this model accounts for:

the main effect of treatment and time and
the interaction between the two?
What would be the difference of m1 from m2?

m2 <- lmer(CO2~days*treatment+(1|replicates),mydata)

Thank you


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