In romantic novels the setting are often described as being on or near a type open peat-rich wasteland what is this desolate tract of land called?

The desolate tract of land you're describing is most likely a moor.

Moors are open, often windswept areas of heathland dominated by grasses, heather, and other low-lying vegetation. They are typically found in areas with acidic, peat-rich soils, which are often associated with a damp, misty atmosphere.

This combination of wild beauty, solitude, and sometimes eerie atmosphere makes moors a popular setting for romantic novels, especially those with Gothic or dramatic themes.