It's likely that after a few rotations of these trees, soils will be drastically reduced in their abilities to support any kind of plant growth. Mick Petrie There has been a huge increase in the amount of mutant tree research worldwide over the past few years. US consumers use 800 pounds per year of paper products. Herbicide tolerance is the primary area of research at this time. Herbicide tolerant trees allow heavy use of Roundup to control competition with weeds during the trees' early development.
Bt production is also very important.
Trees engineered with Bt have the toxic product of the bacteria in all cells. Ingestion of the toxin by soil micro-organisms has been shown to kill these life forms as well as the insects that eat leaves and twigs. Low lignin content is a high research priority because one third of the dry weight of wood is lignin, which cannot be used by the pulp industry. Of course lignin gives trees their rigid structure. Rapid growth is another desirable trait for obvious reasons.