The Scottish Alder Tree is a species of tree native to Scotland and other parts of Europe. Its scientific name is Alnus glutinosa, and it is commonly referred to as the Common Alder or Black Alder. It is an important part of Scotland's natural landscape and is often used for timber and firewood. The acronym ARN stands for Alnus glutinosa, the scientific name of the Scottish Alder Tree, while TREE is the four-letter word for the species.