[__MatrixMan__]

I'm skeptical that the soil in a lumber forest will remain viable for growing trees indefinitely. Crop rotation and fallow is necessary for sustained growth of other crops, it's probably necessary for trees too, just on a larger timescale.

[kayodelycaon]

Crop rotation is needed for yearly crops that deplete soil. By harvesting them, you’re removing the nutrients.

As I understand it, you’re not taking any significant amount of nutrients when you harvest the trunks of trees and leave the branches behind to replenish the soil.

Controlled burning can also be used to speed up the process. Some species of pine trees actually require fire to reproduce.

There are questions about making the soil more acidic. Pine trees grow better in acidic soil. Correlation is not necessarily causation.

[__MatrixMan__]

Lignin is C31H34O11, all stuff that the tree can get from air and water, so you've got a point there.

But a tree trunk is more than just lignin. Also it could be more complex than whether you're robbing the soil of nitrogen and phosphorous. There's a lot we don't know about the role of soil microbiota, for instance. I don't have any evidence that it's going to be a problem, but nobody has evidence that it's not going to be a problem either (only that it hasn't yet).

Although I guess this is all orthogonal to whether, once you've harvested the wood by whatever means, you process it into something stronger and denser.