Yea the fir trees
browsh  (ber-osh')
a cypress (?) tree; hence, a lance or a musical instrument (as made of that wood) -- fir (tree).
samach  (saw-makh')
probably to brighten up, i.e. (figuratively) be (causatively, make) blithe or gleesome
at thee and the cedars
'erez  (eh-rez')
a cedar tree (from the tenacity of its roots) -- cedar (tree).
of Lebanon
Lbanown  (leb-aw-nohn')
(the) white mountain (from its snow); Lebanon, a mountain range in Palestine -- Lebanon.
saying Since thou art laid down
shakab  (shaw-kab')
to lie down (for rest, sexual connection, decease or any other purpose)
no feller
karath  (kaw-rath')
to cut (off, down or asunder); by implication, to destroy or consume; specifically, to covenant
is come up
`alah  (aw-law')
to ascend, intransitively (be high) or actively (mount); used in a great variety of senses, primary and secondary, literal and figurative (as follow)
against us