(IP (NP-SBJ (-NONE- *pro*))
(VP (PP-DIR (P 由)
(NP (PN 此)))
(VP (VV 可)
(VP (VV 知)
(NP-OBJ (CP-APP (IP (NP-SBJ (NN 先民))
(VP (VP (VV 伐)
(NP-OBJ (NN 木)))
(VP (VV 垦荒))))
(DEC 的))
(NP (NN 艰辛)))))))
ARG0: 先民
REL: 垦荒