Jerry S. notes:

http://www.woodbin.com/calcs/s=ADagulator.htm

If you put 5000 lbs on a 30" x 12" x .5" l.d. MDF shelf, it deflects
70.33".
I never knew the stuff was so stretchy. :-P


BTW, I didn't see poplar listed.

Right at the end, yellow poplar. I'd guess that aspen is roughly
similar, as is southern magnolia.