Three potential taxes on this transaction:
1. Stamp duty-you pay this- there will be stamp duty which is assessed on the value of the land.
2. CAT or gift tax- again, you pay this-you have a threshold of 30150 to take from an uncle so, assuming you have not received any other gifts which have used up part of that threshold in the past, if the land is valued under that, no tax, but any part above that figure is taxable at 30%.
3.CGT or capital gains tax- this is a potential tax for your uncle. He would have to consult his own tax advisor about this. There are some reliefs available depending on the circumstances.
For a resource to read more, have a look at the revenue.ie website about each tax, or better still, consult a tax advisor who will be able to advise on the specific circumstances.