Yes if the visitor clicks on the ads on the first page itself, it will add up to your bounce rates. Sites will normally see an increase in bounce rate after adding adsense to the it. Some site with bounce rate of 40% suddenly change to 60% after putting adsense. Ideally do not put ads on landing page to decrease your bounce rate, unless you are mainly planning to make money from online ads.
Just think about a bounce as an event when user leaves your website - closes it, follows a link outside, navigates away himself, etc.
What is Bounce Rate? Basically it is a function of the visitor's interest in the content of your page/website versus the quality of your content. Linkage: http://www.websitehomework.com/what-is-bounce-rate.html