樹幹 is read as じゅかん (jukan) and means trunk.
じゅかん
jukan
じゅもく
tree
き
wooden clappers (signalling the beginning or end of a performance)
じゅりつ
establishment
じゅひ
bark (of a tree, etc.)
じゅれい
age of a tree
じゅし
resin
じゅりん
forest
じゅじょう
up in a tree
じゅかい
sea of trees
じゅしかこう
resin treatment
じゅえき
sap
じゅひょう
frost-covered trees