Hi

Is it recommended to glue the mitered joints of the hardwood nosing? Will the expansion or contraction of the wood cause to crack over time?

Thanks
Marko

Glue can be very effective for holding hardwood and trim in place. Every wood floor is susceptible to major changes in humidity. An acclimated floor will be less susceptible to movement as the flooring can move across the rows of flooring seasonally. Most wood used for flooring will not ever expand lengthwise.
I always glue nosing whether there is a mitered joint or not.