The excellent article, "Fire: Your Partner in Survival, by Pledger" mentioned the BTU ratings of certain trees. Wanting to know a bit more, I did some searching and found a chart of the BTU ratings of various types of wood.
On another note, Pledger's reference to a cord as 4x8 feet by 16 inches threw me. I looked it up and found that a "full cord" measures 4x4x8 feet, which is the number I was familiar with, ranging from 80 to 100 cubic feet stacked. The web site I found uses 90 cubic feet for its BTU ratings. However, a "face cord" is one-third of a full cord and measures 4x8 feet by 16 inches. This is the one Pledger's article uses. - Larry X.