YES

Problem:
 concat(leaf(),Y) -> Y
 concat(cons(U,V),Y) -> cons(U,concat(V,Y))
 lessleaves(X,leaf()) -> false()
 lessleaves(leaf(),cons(W,Z)) -> true()
 lessleaves(cons(U,V),cons(W,Z)) -> lessleaves(concat(U,V),concat(W,Z))

Proof:
 DP Processor:
  DPs:
   concat#(cons(U,V),Y) -> concat#(V,Y)
   lessleaves#(cons(U,V),cons(W,Z)) -> concat#(W,Z)
   lessleaves#(cons(U,V),cons(W,Z)) -> concat#(U,V)
   lessleaves#(cons(U,V),cons(W,Z)) -> lessleaves#(concat(U,V),concat(W,Z))
  TRS:
   concat(leaf(),Y) -> Y
   concat(cons(U,V),Y) -> cons(U,concat(V,Y))
   lessleaves(X,leaf()) -> false()
   lessleaves(leaf(),cons(W,Z)) -> true()
   lessleaves(cons(U,V),cons(W,Z)) -> lessleaves(concat(U,V),concat(W,Z))
  Usable Rule Processor:
   DPs:
    concat#(cons(U,V),Y) -> concat#(V,Y)
    lessleaves#(cons(U,V),cons(W,Z)) -> concat#(W,Z)
    lessleaves#(cons(U,V),cons(W,Z)) -> concat#(U,V)
    lessleaves#(cons(U,V),cons(W,Z)) -> lessleaves#(concat(U,V),concat(W,Z))
   TRS:
    concat(leaf(),Y) -> Y
    concat(cons(U,V),Y) -> cons(U,concat(V,Y))
   Matrix Interpretation Processor: dim=3
    
    usable rules:
     concat(leaf(),Y) -> Y
     concat(cons(U,V),Y) -> cons(U,concat(V,Y))
    interpretation:
     [lessleaves#](x0, x1) = [0 0 1]x0 + [1 0 0]x1,
     
     [concat#](x0, x1) = [0 1 0]x0,
     
                      [0 1 0]          [0]
     [cons](x0, x1) = [0 1 0]x0 + x1 + [1]
                      [0 1 1]          [1],
     
                        [0 1 0]     [1 0 0]  
     [concat](x0, x1) = [1 1 0]x0 + [1 1 0]x1
                        [0 0 1]     [0 0 1]  ,
     
              [1]
     [leaf] = [0]
              [0]
    orientation:
     concat#(cons(U,V),Y) = [0 1 0]U + [0 1 0]V + [1] >= [0 1 0]V = concat#(V,Y)
     
     lessleaves#(cons(U,V),cons(W,Z)) = [0 1 1]U + [0 0 1]V + [0 1 0]W + [1 0 0]Z + [1] >= [0 1 0]W = concat#(W,Z)
     
     lessleaves#(cons(U,V),cons(W,Z)) = [0 1 1]U + [0 0 1]V + [0 1 0]W + [1 0 0]Z + [1] >= [0 1 0]U = concat#(U,V)
     
     lessleaves#(cons(U,V),cons(W,Z)) = [0 1 1]U + [0 0 1]V + [0 1 0]W + [1 0 0]Z + [1] >= [0 0 1]U + [0 0 1]V + [0 1 0]W + [1 0 0]Z = lessleaves#(concat(U,V),concat(W,Z))
     
                        [1 0 0]    [0]         
     concat(leaf(),Y) = [1 1 0]Y + [1] >= Y = Y
                        [0 0 1]    [0]         
     
                           [0 1 0]    [0 1 0]    [1 0 0]    [1]    [0 1 0]    [0 1 0]    [1 0 0]    [0]                      
     concat(cons(U,V),Y) = [0 2 0]U + [1 1 0]V + [1 1 0]Y + [1] >= [0 1 0]U + [1 1 0]V + [1 1 0]Y + [1] = cons(U,concat(V,Y))
                           [0 1 1]    [0 0 1]    [0 0 1]    [1]    [0 1 1]    [0 0 1]    [0 0 1]    [1]                      
    problem:
     DPs:
      
     TRS:
      concat(leaf(),Y) -> Y
      concat(cons(U,V),Y) -> cons(U,concat(V,Y))
    Qed