Silviculture is the art and science of growing trees. In general, forest stands are managed using silvicultural practices to attain some target balance of production and ecological function. This can span the range from clearcutting to a complete 'hands-off' preservation approach. Active management approaches generally vary depending on the desired outcome and existing community, but generally range from clearcutting to maintain early successional habitat and promote high production; to single-tree selection systems which favor late-successional communities and high quality timber products.

Forest growth is generally a function of three things - tree density (absolute measure, in the number of stems per unit area), tree size, and site quality.

- we may be able to leave out site quality; otherwise it's a location-specific attribute that won't change throughout the gameplay, and could be potentially just be randomly assigned

- Forests need to be actively managed to reach maximum production. Without periodic thinning to provide growing space, stands tend to stagnate and stop growing (or at least grow very slowly)

Even-aged stands

Even-aged stands generally constitute those stands that consist of a single age/size cohort. These stands originate from a single disturbance event, such as a clearcut, fire, or blowdown. Management and growth of these stands is generally more straightforward than uneven-aged stands, and typically consists of growing a homogeneous stand until rotation age, then cutting the whole thing and starting from scratch. Intermediate thinnings of these stands keeps growth rates high and produces a small amount of return between harvests. Most intensively-managed forest stands are even-aged. These stands are generally limited to early-successional species (most pine, aspen, white birch), and are usually lower-value products (pulp, framing timber, popsicle sticks*).

*There is (was?) actually a popsicle-stick mill in Rhinelander, probably supplied much of the demand for either white birch or aspen. I can't recall all the details, but easy enough to find out if relevant.

Uneven-aged stands

Uneven-aged stands typically result as individuals within an even aged stand die and trees grow up in there place. Consequently, it can take a long time for this structure to develop, but there are silvicultural practices that can encourage and maintain this type of structure. Generally, this structure will consists of a different suite of tree species, which results in a different suite of understory vegetation and utilization by a different suite of critters. Unlike an even-aged stand, the stem diameters within an uneven-aged stand are not normally distributed, but generally take on a 'reverse-j' shape, typified by lots of small diameter trees and relatively few larger trees. Management in these stands typically consists of periodically extracting a small number of stems at a more frequent interval, and typically produces higher-value species (oak, maple, yellow birch, white pine)

Related Topics

Modeling Forest Growth and Yield

Additional Resources

The forest service has developed a web-based overview describing forest management, which includes a nice series of visuals describing different standard silvicultural practices

The silviculture and forest aesthetics handbook is an invaluable tool that describes most of the information that a practicing forester would use to guide forest management decisions