Repeated, Spatial & Temporally Nested Design Confirmation I'm an ecology grad student struggling to confirm proper analysis for the following experimental design:
I identified 3 spatial blocks, each containing the same 3 plant types (tree, grass, shrub). There was only a single representative of each plant type within each block (9 representatives total). I measured %nitrogen of leaf tissue 10 times (date) with an irregular frequency on the same representatives.
I am interested in the plant type effect & the interaction effect of plant type & date. I would like to know if there was an effect of block and/or date. I include subject to account for its respective variation.
I believe the following model would be appropriate:
%nitrogen ~ (1|Block) + (1|Block:Subject) + (1|Date) + Vegetation + (1|Vegetation:Date)
...such that %nitrogen = response; Vegetation = fixed factor; & Block, Subject, & Date are random factors (as well as all interactions containing a random factor)
Is my nesting appropriate? Are my factor designations for "random"/"fixed" appropriate?      
 A: [response] ~ (1|Block) + (1|Block:Subject) + (1|Date) + Vegetation + (1|Vegetation:Date)
You don't have sufficient levels of Vegetation to treat it as random, and you have also stated that it is fixed, so even philosophically, you shouldn't include it as a random effect.
You also don't have sufficient levels of Block to treat it as a random effect either.
A better model would be:
[response] ~  Vegetation*Date + Block + (1|Subject)
This will estimate fixed effects for Vegetation, Date and their interaction, while controlling for the repeated measures within Subject by estimating random intercepts.
Since you have 10 dates and 3 vegetations, this will result in quite a lot of interaction terms (18), if you code Date as a factor. If Date is numeric (for example the number of days since the experiment began), this will enable you to model the (linear) change in the response as a function of time. You could then also allow the effect of time to vary for each Subject with a random slope: (Date|Subject). You could also add a quadratic term for to cater for non-linear change. 
