Sweet Root Natural Area is a section of the Buchanan State Forest, located near Chaneysville, Pennsylvania. As a state-designated Natural Area, Sweet Root is protected from almost all development, including roads and power transmission lines. The reserve protects the upper reaches of Sweet Root Run and the water gap it has carved through Tussey Mountain. The gap contains a old-growth forest of Eastern Hemlock, Sweet Birch, Eastern White Pine, American Basswood, and White and Red Oak, but the hemlock trees are being devastated by the Hemlock woolly adelgid. The remains of an early mill and a saltpetre cave from the Revolutionary War are also within the Natural Area. The saltpetre was used in the production of gunpowder. Current reserve size is .