Maintain an ongoing dialog with employees on company results, and targets.  Focus on individual and team goals.  As long as these goals are clear and employees get regular feedback, personnel changes will not be as surprising and individuals will know their own value.

Whenever there are changes your employees will question what will be next, how will they be impacted, and does this mean they could lose their job or the position they have established for themselves on the team.

This is a big deal and should not be taken likely by you as a manager.  You need to address issues both as a team and individually.  If your organization goes through staff changes often, it may make sense to create a system within your team to manage these transitions.  That way they are not left with questions each time, but they understand the flow of things, the discussions that will take place and the sensitivity of the subject.  They need to feel respected and by making a formal process you will show them that respect.