In order to answer that question, you need to know what Succession Planning and Human Resource Planning represent.
Succession planning is a method by which businesses make sure there is an orderly transfer of duties, power and job functions when an executive or management employee retires or in one way or another leaves the company. This type of planning identifies the positions and roles where probable vacancies will happen and come up with the best plan to fill these positions.
The planning process for human resources makes sure that the best fit of personality and skills are available in order for the company to succeed in meeting its strategic, short-term goals. Succession planning is a part of this larger process. So, by comparison, the Succession Planning is to the HR Planning as the seed is to the apple. The one is part of the other!