I. Tesari et C. Mattheck, The adaptation of the compression strength of hardwood branches to the loading caused by gravity, ALLG FORST, 170(7), 1999, pp. 128-132
Branches are permanently loaded by their weight and there is temporarily ad
ded the weight of the leaves or snow. Hence bending stresses result which c
ause tension in the wood of the upper side of the branches and compression
in the under-side. Measurements of the compression strength of hardwood bra
nches show that the strength is adapted to the load. At the compression loa
ded underside was measured a higher averaged compression strength than at t
he upper side. Comparisons with the compression strength in trunks show tha
t this is an optimization and that it is not only caused by reduced strengt
h of the tension wood in the upper side of the branches. This increase of c
ompression strength is probably caused by the thicker lignified cell layers
of the wood in the under-side. The width of annual rings seems not to be r
elevant for the compression strength in branches.