

Hi,  

I am applying a mixed model to calculate the variance components of different factors in our seagrass data. The model i was using looks something like:  

POMI14_vc <- lmer(POMI_14 ~ Depth + surveyor + (1|region/site/zone) + (1|year), 
 data = P_oceanica) 

When I apply this model, however, year comes out with SD = 0. Year, in this data set signifies inter-annual variation (in the health status of seagrass meadows), of which there is a considerable amount. That makes me believe that there is is a feature of the model which is 'absorbing' the inter-annual variation.  

Can you suggest why this may be occuring? What modifiations could i use to fix this?   

kind regards  

Scott Bennett 
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