Well, the answer to this question depends a lot on which version of the poem you are referring to. Dickinson wrote two, and they are both markedly different. Stanza one is virtually the same in each version. The dead lie in their graves, finally "safe" from the world, awaiting resurrection. This image of the dead is juxtaposed in the first version of the stanza two with images of a joyful natural world, and in the second version with images of a cold and indifferent universe.
The first word of the poem, "Safe," might give a certain smug confidence to the "elect" that the poem suggests may not be justified. The unjustified smugness may also be implied by the manner in which the soft but heavy alliterative "m" of "meek members" is offset by the harder alliterative "r" of "Rafter" and "Roof." They may have their satin-lined coffins and their confidence in resurrection, but their reality is suggested by the way they are cut off from all vitality and sensation by the "Roof of Stone." The dead, in their "Alabaster Chambers," seem suspended in some cold white prison. They are untouched by "Morning," associated by hope, or by "Noon," which we might associate with fulfilment and intensity.
However, in the earlier version, stanza two contrasts the coldness and suspension of the dead with the vibrancy and activity of nature. The alliterative effects now change to support this sense of vibrancy as is demonstrated in such phrases as "Light laughs the breeze" and "Babbles the Bee." Perhaps Dickinson is using these natural images to offer consolation in the fact that in spite of the death of the individual life goes on and the cycle continues.