Do child .htaccess file overwrite their parent .htaccess files?

[OrahChris]

I have an .htaccess file in my root domain something.com. I also have an .htaccess file in a sub folder: something.com/forum/ The root has wordpress and the sub folder contains IPB

I want to ensure that the .htaccess rules in my root domain (wordpress) don't leak into the forum sub folder causing problems. 

How do I ensure the root .htaccess file doesn't place any rules on the forum?