Model selection for random effects: can unselected random effects be used as fixed effects?

I am working on a mixed effects model. What I would consider random effects are year, sampling transect, and sampling location. There are multiple collections taken along each transect, and multiple transects were taken each year. The "full" random effect structure would be ~1|year/transect/collection. I have been taught that you can select the best random effects structure by comparing the AICc of competing models with different random effects structures (using REML rather than ML and using the full fixed effect structure). I ran the competing models, and in my case, the "best" random effect structure is ~1|collection. However, year is still likely an important variable in my analysis. Would it be bad form to add year to my fixed effect structure? It seems reasonable enough to me, but I'd like to know what is the proper thing to do in this scenario.

For your final question: It would not be bad form to use year in your fixed effect. Nevertherless if the year|collection random-effects structure makes the most sense conceptually; use it. It reflects reasonable assumption, you control for a time-evolving trend everyone expects, end of the story. No $p$-value / likelihood-ratio test etc. is above your understanding of the problem at hand. You might want to comment for the reasons certain things appear statistically insignificant but that is another question. Check this excellent thread on "what is the upside of treating a factor as random in a mixed model?", I think it will aid your understanding further.
• Cool, saw your edit. In any case: If you do not expect a time-evolving trend why would you expect yearly differences for a reason other than random fluctuations? As I said, random effects are usually related to the experimental design, maybe you should not try to select your random effects. Also using something like 1|year/... implies you are treating time (in years) as a discrete variable; that is a bit dubious when it comes to time which is clearly continuous. – usεr11852 Jan 4 '16 at 17:59