Wood Stiffness

Wood stiffness or modulus of elasticity (MOE) is a measure of the elastic resistance to bending under an applied load.  In structural applications it is one of the major determinants of quality and hence value of timber.  In general about 50% of the variation in stiffness is explained by basic density.  50% is also explained by variation in microfibril angle (MFA).  Together basic density and MFA explain 80-85% of the variance in stiffness.

See also https://www.fpl.fs.fed.us/documnts/pdf2001/green01d.pdf