Maggie,
This is one of the areas where I think the PMBOK Guide 3rd edition was "better" than the new PMBOK Guide 4th edition. In the 3rd edition you had a process for every one of these "management plans".
In the 4th edition you will find statements like the following:
"Although not shown here as a discrete process, the work involved in performing the six processes of Project Time Management is preceded by a planning effort by the project management team. This planning effort is part of the Develop Project Management Plan process (Section 4.2), which produces a schedule management plan that selects a scheduling methodology, a scheduling tool, and sets the format and establishes criteria or developing and controlling the project schedule."
So the guide recognizes that we need to create these plans. For some it calls out a specific process for others you will see a similar statement as the above.