If I am ranking high for long tail keyword then Will I rank on short tail keywords too?

Not really!

Short tail keywords are already covered in the long tail.

Long tail and short tail keywords are both very different, but essential in SEO. Long tail keywords contain three or more words and are much more specific than short tail keywords. Consequently, it's common that long tail keywords will rank higher than short tail keywords because they are more specific, and when users search for specific terms there is less competition. Having said this, short tail keywords are also important, despite having much higher competition. It's important that you utilise an effective combination of long tail and short tail keywords in your SEO strategy.