Robustness of multiqubit entanglement against local decoherence

We investigate the disentanglement dynamics of generalized multiqubit Greenberger-Horne-Zeilinger-type states parallel to Psi(n,N)>=alpha parallel to 1 >(circle times n)parallel to 0 >(circle times(N-n))+beta parallel to 0 >(circle times n)parallel to 1 >(circle times(N-n)) (with 1 <= n < N) in a local decoherence environment. By adopting the time after which all the bipartite entanglements vanish or become negligibly small as the criterion of entanglement robustness, we show that states parallel to Psi(n,N)> are more robust than states parallel to Psi(N)>=alpha parallel to 0 >(circle times N)+beta parallel to 1 >(circle times N) in all respects. Since the two states parallel to Psi(N)> and parallel to Psi(n,N)> can be transformed into each other by local operations, we confirm that entanglement robustness can be enhanced by local operations though the amount of entanglement cannot.