Here’s a puzzle: Cut down half the ponderosa pines on an acre of land and you end up with just as much wood as when you started — eventually.
The counter-intuitive result comes from a long-term study of the growth of trees on 168 different plots of land between 1944 and 1988, reported in the Canadian Journal of Forest Research.
A research team led by Dr. Jianwei Zhang from the U.S. Forest Service’s Pacific Southwest Research Station wanted to know what affect thinning ponderosa pine forests and removing undergrowth would have on total wood production.
Turns out, removing most of the brush and half of the trees made the remaining trees grow so much bigger and faster that in the end you ended up with just as much biomass as before you thinned — except now you had a much lower risk of catastrophic crown fires.
The researchers found that in stands suffering from significant tree death from things like beetles and mistletoe, you could thin even more severely and end up with more wood than you started with — apparently by limiting the spread of disease and infestation to surviving trees.
The aggressive thinning also significantly reduced the buildup of fuel on the ground. That would make wildfires much less destructive, since fires that consume large buildups of dead wood and brush on the ground can effectively sterilize the soil — and make it less able to absorb water.
Moreover, the researchers concluded that removing shrubs from the understory when combined with thinning also boosts overall tree growth — apparently by reducing the competition for water. Thinning a stand and removing the brush also results in a net reduction in the release of carbon into the atmosphere, by reducing both wildfires and wood decay.
The long-term findings based on carefully measuring the growth rates and biomass of tens of thousands of trees bolsters the Forest Service’s recent emphasis on thinning projects to restore forest health.
The Forest Service has awarded a contract to Good Earth to thin 300,000 acres in and around Rim Country in the next decade.
The plan calls for the international forest management and energy company to dramatically reduce tree densities by focusing on removing small trees and brush and converting them into jet fuel and finger-jointed furniture.
This most recent research supports that concept and demonstrates that not only will properly managed thinning projects reduce wildfire risk, they’ll actually increase the timber value of the trees that remain without any net loss of biomass.