Coppices

I have recently been trying to obtain my newest S assignment, which is "add 40 references to your model background by Wednesday" by reading and seeking out some lovely documentation from CU's massive CAFLS access. Of course, for every one relevant article I read, I also read 3 that I think "oh, these are interesting, but how will I ever use that?" Well, this is about one of those articles...

With my study of urban forests, one thing I have failed to think about is coppice. Let me explain. Timber forests are often grown for height and trunk thickness; a "tall, straight bole" is considered to be the best kind of tree. If your tree has even a slight krick in it, you will lose value and grades because you get less boards out of it and the grain alignment is off, which reduces some of the wood products properties. For example, wood has the most tensile strength "with the grain"-- which means if you have to cut your boards with an angle, you'll lose strength, and when you lose strength, you lose grade, and when you lose grade, you lost money... it's all a cycle.

The opposite is true in urban forestry. Wood is not even a concern, really, so trees, yes, are grown for height, but their breath (crown diameter and crown height, and to some extent, I guess you could include LSA) is really of value. I see my dad trimming the crape-myrtle at home all the time, when I ask why, it is because "it grows more." What he doesn't realize is that he is actually practicing a silvicultural technique that was very prominent in the medieval days and also in Japanese forestry: coppice.

The idea of coppice is to promote wide, low growth trees. These trees, obviously, are not being grown for timber, but for other products. Early coppicing was used to get charcoal and wood for fuel. Recent silvicultural practices (including one of my favorite sites on the CEF) use the coppice with standards technique, which is where you have a sparse level of older, tall growth over a level of low growth. "Biomass" is the hit word right now in our field, so obviously this is going over very well. Let's say you have a hardwood forest and you want to grow timber trees but you also want steady cash flows... oh, it's so easy! You plant oaks, let them grow tall, and maintain a lower level forest of, say, maple or beech. You harvest the maple or beech frequently for biomass products by simply performing a massive prune. This is different than say, seed tree, when you've only got a few trees in your upper level-- in coppice with standards you've got about a 50% full overstory and a completely full understory.

So what does this have to do with urban forestry? Well, most of the valuation strategies I've been doing have been, somewhat, based on strategies used in traditional timber situations-- not coppicing. But I wonder-- an urban forest behaves much more like a coppice-- its value is based on breadth/crown size/ almost "biomass" versus timber. I wonder, when looking at some of the measurements that are used for urban forests, whether or not we shouldn't view it through the lens of coppice?

This is something to think about. Perhaps something to think about AFTER I've finished the work I'm currently doing. In the meantime... coppices for the win.