(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